Conference PaperPDF Available

A Wind-powered Rover for a Low-Cost Venus Mission


Abstract and Figures

Venus, with a surface temperature of 450°C and an atmospheric pressure 90 times higher than that of the Earth, is a difficult target for exploration. However, high-temperature electronics and power systems now being developed make it possible that future missions may be able to operate in the Venus environment. Powering such a rover within the scope of a Discovery class mission will be difficult, but harnessing Venus' surface winds provides a possible way to keep a powered rover small and light. This project scopes out the feasibility of a wind-powered rover for Venus surface missions. Two rover concepts, a landsailing rover and a wind-turbine-powered rover, were considered. The turbine-powered rover design is selected as being a low-risk and low-cost strategy. Turbine detailed analysis and design shows that the turbine can meet mission requirements across the desired range of wind speeds by utilizing three constant voltage generators at fixed gear ratios.
Content may be subject to copyright.
American Institute of Aeronautics and Astronautics
A Wind -powered Rover for a Low-Cost Venus Mission
Gina Benigno1
Towson University, Towson, MD 21252
Kathleen Hoza1
Massachusetts Institute of Technology, Cambridge, MA 02139
Samira Motiwala1,2
Stanford University, Stanford, CA 94305
Geoffrey A. Landis,3
NASA John H. Glenn Research Center, Cleveland, OH 44135
Anthony J. Colozza4
Vantage Partners LLC, Cleveland, OH 44135
Venus, with a surface temperature of 450°C and an atmospheric pressure 90 times higher
than that of the Earth, is a difficult target for exploration. However, high-temperature
electronics and power systems now being developed make it possible that future missions
may be able to operate in the Venus environment. Powering such a rover within the scope of
a Discovery class mission will be difficult, but harnessing Venus’ surface winds provides a
possible way to keep a powered rover small and light. This project scopes out the feasibility
of a wind-powered rover for Venus surface missions. Two rover concepts, a landsailing rover
and a wind-turbine-powered rover, were considered. The turbine-powered rover design is
selected as being a low-risk and low-cost strategy. Turbine detailed analysis and design
shows that the turbine can meet mission requirements across the desired range of wind
speeds by utilizing three constant voltage generators at fixed gear ratios.
Arotor = Rotor area
Ablades = Blade area
Asail = Blade area
AR = Aspect ratio
b = Sail luff height
CD = Drag coefficient
CL = Lift coefficient
Cr = Rolling resistance
CP = Center of pressure
Fp = Propulsive force
Fs = Sail force
g = Gravitational acceleration
h = Height
1 NASA Space Academy 2012, NASA Glenn Research Center, Cleveland OH
2 AIAA Student member
3 NASA John Glenn Research Center, mailstop 302-1, 21000 Brookpark Road, Cleveland OH 44135. AIAA
Associate Fellow
4 Vantage Partners, LLC, John Glenn Research Center, mailstop 309-1, 21000 Brookpark Road, Cleveland OH
American Institute of Aeronautics and Astronautics
l = Sail length
L = Characteristic length of rotor blade
m = Rover mass
mblades = Rotor blade mass
mtower = Turbine tower mass
n = number of rotor blades
P = Power
Pmax = Maximum available power
Pkinetic = Kinetic power
r = Rotor radius
R = Radius of Venus, 6051.2 km
Re = Reynolds number
S = Sail surface area
t = Time taken to complete one full orbit
TSR = Tip speed ratio
Vapp = Apparent wind speed
Vblade = rotor blade speed
VC = Circular velocity
Vwind = True wind speed
α = atmospheric absorption
γ = Viewing angle from center of Venus
λ = radio wavelength (cm)
µ = Standard gravitational parameter
µv = kinematic viscosity of Venus atmosphere
ρ = Atmospheric density
I. Introduction
Venus is one of the more scientifically interesting planets in our solar system, yet is relatively unexplored, and
much is still unknown about the planet. While similar in size, density, and surface gravity, Venus is also quite
different from our own planet, Earth. It has a surface temperature of 464°C, and an atmosphere mainly composed of
Carbon Dioxide (96.5%) and Nitrogen (3.5%) at surface pressure of 92 Bar.1
These surface conditions make design of a spacecraft to penetrate the Venusian atmosphere difficult. Previous
missions to the Venusian surface have been quickly destroyed by the extreme surface temperature and pressure. The
longest-lasting spacecraft on the Venusian surface to date is the Russian Venera 13 lander, which managed to
survive Venus’s surface conditions for 127 minutes before losing its connection with Earth.
Most electronics designed for use on Earth are not able to withstand surface temperatures upwards of 400°C;
however, several institutions are successfully developing high-temperature electronic components, using silicon
carbide and other wide-bandgap semiconductor based electronics.2 Currently, they have successfully tested silicon
carbide based electronics at 500°C 3 for extended periods of time. The further developments of these silicon-carbide
based electronics will be invaluable for future missions to Venus.4 They will contribute to not only the scientific
instruments, but also communications systems, as well as potential mechanical systems for a Venus rover.5
Venus’s opaque atmosphere makes it difficult to study the surface from space, except by radar images. Magellan
was able to successfully map out 98% of Venus’s surface,6 however, only so much can be discovered about a planet
by images taken from orbit; detailed exploration requires “ground truth” to be established from surface missions.
Whereas short-lived probes have successfully landed on the surface of Venus, a rover has yet to be sent there.
Recent Mars missions have shown the value of rovers on planetary surfaces, allowing the ability to do observations
at multiple locations, rather than being stuck to just the landing location. A rover may also have the ability to scrape
under the surface of Venus; it is likely that the rocks and soil are chemically altered through interaction with the
atmosphere of Venus. Being able to study underneath the soil and the insides of rocks could provide us with entirely
new information by accessing samples unaltered by contact with the Venusian atmosphere.
With the use of high-temperature electronics, the goal of this rover mission is to be able to survive for many
days. A longer lifetime means a much longer record of atmospheric and surface conditions can be taken, covering a
large part, if not all, of a Venus solar day.
Fig. 1 illustrates an artist’s conception of this conceptual design for the Venus rover.
American Institute of Aeronautics and Astronautics
Figure 1. Artist’s Conception of Venus Rover
II. Venus Rover Concept
High surface temperature conditions on Venus poses a significant challenge to designing a Venus power
systems. Previously proposed rover designs7,8 implemented the use of radioisotope power systems, which produce
power by converting the heat from radioactive decay into electricity, using either thermoelectric conversion
(“Radioisotope Thermoelectric Generators,” or “RTG”)9 or Stirling10 conversion technology. Although they have
been proposed for use on Venus,11 radioisotope power systems are expensive and heavy,12 and also may have
difficulties operating in the corrosive, high-temperature, high-pressure environment of Venus, which may makes
them unsuitable for a Venus mission. The cost and lack of availability of the plutonium isotope make them a poor
choice for a low-cost, Discovery class mission.
In this design study, we analyze an alternative method for generating power: harnessing the wind on Venus as a
power source for a rover. Wind speeds on the surface of Venus have been directly measured only at four sites on the
Venus surface, at which the Venera probes found13,14 speeds in a range of 0.3 to 0.9 m/s. Although the absolute
speed is slow compared to winds on Earth, the density of the Venus atmosphere is high enough that this wind can be
used to generate force.
This study analyzed two main rover concepts: a landsailrover and a wind turbine-powered rover. These
concepts rely on surface winds to generate power for the scientific instruments and for mobility. Design assumptions
for these concepts include wind speeds of 0.3 m/s (worst-case scenario) and 0.6 m/s (most likely or average case
scenario), a rover base mass of 70 kg, rolling resistance of 0.05 (the equivalent of a stagecoach on a dirt road),
power requirements of 30 Watts for scientific instruments, and total energy of 233 W-h per science stop.
A. Landsailer Design
The Venus landsailer concept is in essence a sailboat on wheels, as depicted in Fig. 2.15 The sail can be treated
as an airfoil, which develops aerodynamic forces as air flows past the sail. These forces may be decomposed into
components of lift and drag, perpendicular and parallel to the airflow, respectively.
The apparent wind speed is the speed relative to the moving vehicle, and is the vector sum of the true wind
speed (wind speed relative to the ground) and the speed of the vehicle relative to the ground.16 However, for the
Venus landsailer, the velocity of the vehicle will be low compared to the wind speed, and hence the apparent wind
speed can be assumed to be equal to the true wind speed, Vwind.
American Institute of Aeronautics and Astronautics
Figure 2. Venus Landsail Concept (from ref. 15)
Thus, the force on the sail can be calculated by the lift equation:
!!!!"#$!! (1)
where ρ is the air density on Venus (67 kg/m3), Vwind is the wind speed, Asail is the sail surface area, and CL is the
aerodynamic coefficient. Although the atmospheric density is high compared to that of Earth, the wind speeds are
much lower, resulting in a similar Reynolds number for the Venus rover in comparison to typical terrestrial sails.
The force required to propel a vehicle depends on the rolling resistance, which is a function of both the terrain
and the wheel type and size:
!=!!!!!! (2)
where Cr is the coefficient of rolling friction, m is the rover body mass, and g is the gravitational acceleration on
Venus (8.87 m/s2). The minimum size of the sail needed to move the rover for assumed parameters can be computed
by setting the two forces equal to each other. Fig. 4 shows a graph of the minimum sail area as a function of mass
for rolling resistance coefficients ranging between 0.02 (rolled new gravel) and 0.08 (medium hard soil), since the
rolling resistance of the rover on Venus is just an assumed parameter for an unknown environment and wheel
The star on Fig. 3 indicates the sail area size for the assumed parameters of 70 kg rover mass and 0.05 rolling
resistance, which yields a minimum sail area of 10.64 m2 needed to move the vehicle.
The sail itself can be dimensionalized by considering different aspect ratios (AR) of the sail. The aspect ratio is
defined as:
!" =!!!
where b is the length of the luff and Asail is the surface area of the sail. The sail may be estimated as a simple
geometric triangle with height b and length l, as shown in Fig. 4.
CP represents the center of pressure, which is estimated as 1/3 the height from the base of the triangle.
Aspect ratios determine the efficiency of the sail, because higher aspect ratios yield lower lift-induced drag. Typical
aspect ratios for terrestrial sails range between 1 and 6; higher aspect ratios generate more lift but experience stall at
high angles of attack whereas lower aspect ratios generate greater drag.16 A polar diagram by Marchaj17 showing lift
versus drag with plotted data for sails for different aspect ratios show that the most favorable aspect ratios for ocean
cruising and maximum performance are between 2.5 and 3.5.
Table 2 shows different aspect ratios and their corresponding lengths and the center of pressure location for the
sail area size determined. Packaging and center of pressure create challenges to sail design, so the lower aspect ratio
of 2 was chosen to keep the height of the mast lower. This results in a triangular sail with a 45° base angle.
American Institute of Aeronautics and Astronautics
Figure 3. Sail Area vs. Mass for Various Rolling Resistances
Figure 4. Sail Geometric Shape
Table 2. Sail Dimensions for Various Aspect Ratios
Asail = 10.64 m2
b (m)
l (m)
American Institute of Aeronautics and Astronautics
Given the center of pressure, the base of the rover needs to be sized so that the force generated on the sail
(approximately 31 Newtons) does not cause the rover to tip and be unable to recover. A base width of 0.35 meters is
required to overcome this force; the width is designed for 0.5 meters to include margin.
Power can generated from two main sources for this conceptual design: work done on the sail from the
aerodynamic force (e.g., acting on a generator attached to the wheels) or from solar cells placed on the sail surface
or on the rover body. The power requirements for the mission are 30 Watts for science instruments and an additional
30 Watts for steering and mechanisms (which need not be operated simultaneously). Wind imparting kinetic energy
onto the sail cannot transfer all of its energy to the sail. The Betz limit dictates the maximum power available for a
wind turbine:16
!"# =!"
!"#$%"& =!"
!! (4)
However, sails are typically only one-fourth as effective as wind turbines in extracting the wind’s energy, and
the maximum power achieved occurs when the rover speed is 1/3 of the true wind speed, where the wind does more
work on the relatively slow-moving vehicle because it is required to “pushharder.16. For this case
!"# =!
!!!"#$!! (5)
where CD is the drag coefficient on the sail.
Solar cells operate poorly at the Venus surface due to both the low light levels and the high temperature.
However, photovoltaic solar cells have been calculated to have some performance on the surface of Venus. Dual-
junction PV solar cells have about 0.2% efficiency at the surface and require an estimated 1.6 m2 of surface area to
generate 1 Watt of power.18 Table 3 summarizes the total power generated from the solar cells (sail and rover) and
from wind energy (propulsion).
Table 3. Available Power
Power Source
Power Generated
Power generated from solar cells can be stored in batteries as charged energy for a long period of time in order to
meet power requirements. If 24 hours are allowed for charging, approximately 330 W-h of energy can be stored and
used for almost 11 hours of either science missions or mobility.
B. Wind Turbine Design
The turbine-powered rover (Figure 1) uses a two-bladed rotor to capture kinetic energy in Venus surface winds.
This energy is converted to electrical energy via a high temperature generator. While Venus surface conditions
present serious challenges for generator function, high-temperature motors suitable for operation at Venus surface
conditions have been developed.19 This design could be modified to run backwards as a generator. Electrical energy
produced would be stored in sodium-sulfur batteries, which can operate at Venus surface temperatures.20 This
energy would then be used to power science instruments and drive the wheels via a high temperature motor.
The power generation of the turbine will be dependent on the power of the air incident upon the turbine disk
area. The total kinetic power of this air is given as:
!! (6)
For a sail, the theoretically extractable power is considerably less than the total kinetic energy of the air, as given
by the Betz limit seen in Eq. (4). Furthermore, unavoidable inefficiencies in the rotor will significantly reduce
actual power production.
Rotor efficiency will have a large impact on the power output of the rover, and it is necessary to estimate the
efficiency of a turbine operating in Venus surface conditions. It is not immediately obvious how well performance
analyses for large commercial turbines operating on Earth will apply to a small wind turbine operating in a high-
density atmosphere. However, in terrestrial wind turbines, efficiency is approximately linear with lift/drag ratio,21
and lift/drag ratio is correlated to the turbine’s Reynolds number, as seen in Fig. 5.
American Institute of Aeronautics and Astronautics
Figure 5. Lift/Drag Ratio vs. Reynolds Number for Terrestrial Wind Turbines
The Reynolds number gives the ratio of inertial to viscous forces, and is defined as:
!" =!!
! (7)
Since the rotor may be moving much faster than the wind speed, we can no longer approximate the apparent
wind speed as equal to the wind speed. Apparent wind velocity Vapp and characteristic length L are both design
variables of the rotor.21 The apparent wind velocity depends on tip speed ratio, which is defined as:
!"# =!!"#$%
Tip speed ratio is tied to rotor efficiency,22 as shown in Fig. 6:
Figure 6. Efficiency as a Function of Tip Speed Ratio (TSR) for a Two-Bladed Rotor
Peak efficiency is achieved when TSR is approximately 6.3. Using a design wind speed of 0.6 m/s and design
TSR of 6.3 gives a design apparent wind speed of 3.8 m/s
American Institute of Aeronautics and Astronautics
The characteristic length L for the rotor blades will depend on solidity, defined as:
!"#$%$&' =!!"#$%&
For a two-bladed configuration, terrestrial wind turbines have efficiency optimized when solidity is ~0.05. 21
Setting solidity equal to 0.05 and using the relationships detailed above reduces turbine efficiency to a function of
rotor area. This allows for calculations of energy stored for a given wind speed as seen in Fig. 8.
The mass is estimated by summing the estimated mass of the turbine tower, blades, and generators. For a given
height, the mass of a tower varies with the square of tower height. Based on known values for terrestrial turbine
tower masses, the approximate mass of the mast for a Venus wind turbine can be interpolated: 23
!!"#$% =3.64! (9)
To leave room for blade clearance of science instruments while keeping the center of pressure low, the tower is
assumed to have a height 30 cm greater than the rotor blade length.
Rotor blade mass scales approximately with the radius raised to the 2.3 power.24 Using a scaling factor of 1.63
based on terrestrial wind turbine data,24 blade mass can be approximated as:
!!"#$%& =!1.63!!.! (10)
Generators are estimated to weigh 0.88 kg each, based on the mass of a demonstrated high-temperature motor.25
When combined, these three components will compose the bulk of the turbine weight and allow for estimation of
turbine mass as shown in the blue curve in Fig. 7.
Figure 7. Turbine Sizing for wind speed 0.6 m/s
Power production is directly dependent on turbine area and a large-sized turbine has the obvious advantage of
providing more power to the rover. However, constraints on mass and packaging make it necessary to keep turbine
size relatively small. Using the methods detailed above to estimate rover size, it seems likely that 5 m2 turbine area
will provide the appropriate balance. At this baseline area of 5 m2 and give 0.6 m/s winds, the turbine will generate
5.2 Watts. Thus, it will take 80 seconds to store enough energy to move 5 meters, and 45 hours to store enough
energy to do one science run.
Assuming wind speed on the Venus surface to lie in the (relatively wide) range of 0.3 to 0.9 m/s, we perform
the analysis varying wind speed while holding area constant at 5 m2, to give the results in Fig. 8.
At the low end of the wind speed range, the turbine will produce 0.59 W, take about 12 minutes to store enough
energy to move, and take ~17 days to store enough energy for one science run. This shows that the 5 m2 turbine will
provide enough power for mission success even in the lowest wind speeds considered. Equally importantly, the
turbine will not tip the rover even at the highest wind speeds.
American Institute of Aeronautics and Astronautics
Figure 8. Analysis of a 5 m2 Turbine
III. Trade Studies and Down-Select
Both Venus rover concepts have their advantages and disadvantages. The landsailer is simpler it has fewer
moving parts and is overall less massive and it has greater aesthetic appeal. However, the motor actuating the mast
would lack precision control and the rover would be difficult to package; the mast would need to be deployable. In
addition, if the unpredictable wind speeds on the Venusian surface causes the vehicle to tip, the mission is
The wind turbine rover is much easier to control with finer precision motors, easier to pack, takes advantage of
higher wind speeds to generate a greater amount of power, and is less likely to tip. Its main disadvantage is the
higher complexity required (more moving parts). It is also more massive than a landsailer and would require a
longer charging time for lowest expected wind speeds (on the order of weeks).
Due to the lower risk, the wind turbine was selected as the Venus rover design concept for this study.
IV. Candidate Science Payload
The designed mission for the Venus rover is to carry a payload of science instrumentation to the surface, and the
detailed design of the mission will depend on the science payload selected. Although designing scientific
instruments for the Venus surface is not part of this study, a notional payload is required to enable the rover design
requirements to be established. Thus, the science package listing here should not be considered the “final” payload
selection, but rather a notional set of payload instruments representative in overall function to what would be
selected for an actual mission. The instrument set here is based on past instruments flown to Mars, with the objective
that the capabilities of this mission would be similar in scope to the scientific mission performed by the MER rovers.
The amount of power available is limited. To be able to get the most out of Venus’s wind speed, a low-mass,
low-power payload is necessary for the rover. This was a significant factor in the instrument set selected here. The
candidate scientific instrument list is shown in Table 1. Several other instruments were considered, but were
removed from the list due to higher mass or power than the design goal required. The resulting instrument list
contains instruments that image the site, measure the chemistry and mineralogy of the surface, and grind or drill
samples that will be taken from Venus’s surface, as well as measure temperature, pressure, and wind speed and
American Institute of Aeronautics and Astronautics
Table 1. Candidate Instrument List
Power (W)5
Size (cm)
Bits per
Temperature (°C)
Alpha Particle X-Ray
Spectrometer (APXS)
8.5 long,
5 diameter
-40 to 5
Calibration Target
10 x 10
X-ray Diffraction (XRD)
30 x 20 x 10
Optimal: -60
Microscopic Imager
12 x 7.5 x 5
Operating: -55 to 20
Non-Operating: -110 to 50
Thermal Emission
Spectrometer (TES)
23.5 x 16.3 x
-45 to 50
Navigation Cameras
.2 x 4
5 x 5 x 10
CCD: -55 to 20
.27 x 2
50 x 60 x 110
Operating: -55 to 20
Non-Operating: -110 to 50
Radar Reflector
50 x 50 x 20
Radiant Heater (Mini-TES)
10 x 10 x 10
Rock Abrasion Tool (RAT)
10 long,
7 diameter
0 - 500
Rover Environmental
Monitoring Station
50 hrs
10 x 10 x 10
-130 to 70
A significant constraint on the instrument design for the rover is the high surface temperature. The candidate
instrument listed are primarily designed to work at temperatures of 20°C and below. Since thus rover is not designed
with a cooling system, it is assumed that by the time this mission is ready to launch, high-temperature electronics
will be available, allowing instruments of similar capability to withstand the extreme Venusian surface temperatures.
To account for the fact that these instruments will be of different design, a growth factor of 150% was assumed on
the mass and power values shown in table 1.
Atmospheric science requirements include data on surface pressure, temperature, and wind speed and direction.
These will be measured using a Rover Environmental Monitoring Station (REMS) instrument similar to that used on
the MSL mission to Mars, incorporating a series of booms containing different sensors to measure meteorological
The Alpha Particle X-Ray Spectrometer (APXS) is typical of instruments to measure the elemental composition
of samples. This is done by analyzing the energy spectrum of the characteristic fluorescent X-rays emitted when a
sample is irritated with alpha particles from radioactive source.27,28,29 While existing sensors for Energy-dispersive
X-ray detectors used in an instrument such as this achieve low noise levels only when operating at low temperature,
the noise floor in a detector is an exponential function of the temperature divided by the bandgap of the
semiconductor used for the detector (typically a p-i-n diode operating at high reverse bias). Thus, the basic physics
implies that by using a wide-bandgap semiconductor for the detector, an acceptable noise level can be achieved at
Venus temperature. Although such high-bandgap avalanche photodiodes are not currently being manufactured,
there is no fundamental reason that they could not be developed.
A Thermal Emission Spectrometer (TES) is typical of a non-contact measurement. TES is a Fourier Transform
Spectrometer that will provide remote measurements of mineralogical as well as thermophysical properties of its
surface surroundings. An example of the effective operation of thermal emission spectroscopy on a planetary rover
is the use of the miniTES instrument on the Mars Exploration Rovers.30 Infrared detectors (bolometers) can operate
at the required temperature, however, to function, the instrument needs to be at a lower temperature than the sample
being analyzed. Due to Venus’s greenhouse effect, objects in equilibrium at the surface are at nearly the same
temperature, meaning the sample will be about the same temperature as the instrument. For the Venus instrument, a
radiant heater will be used instead to heat the sample for the necessary temperature difference. The radiant heater
American Institute of Aeronautics and Astronautics
will be a simple metal halide lamp similar to those used on submersible vehicles.8 These are rated to a depth of
2,000 meters under water, corresponding to a pressure of roughly twice the Venus surface. The heated sample will
emit a unique thermal infrared spectrum, characteristic of the different minerals contained in the sample.30
A third composition and mineralogy tool that could be used on such a rover is an X-ray diffraction tool. An
example of an X-ray diffraction instrument is the CheMin package used on the Mars Science Laboratory to analyze
the crystallographic composition of samples.31 The CheMin expose a beam of X-rays to a sample of rock, and the x-
ray diffraction pattern reveals the crystal structure of the sample. Each mineral has a specific diffraction pattern
which is identified by the angular dependence of the diffracted beams.
One of the desired objectives of a surface science investigation is that the soil and surrounding rocks be studied.
A Rock Abrasion Tool (RAT)32 will be used so that the analysis tools can be used to investigate the chemical
composition and mineralogy of not only surface samples, but also soil that is not immediately exposed to the
Venusian atmosphere, as well as the insides of rocks. The RAT will position itself against a rock or soil surface
using the rover’s arm it is positioned on, and use a grinding mechanism to dig into the rock to expose a fresh sample
that has not been exposed to the Venusian atmosphere. Once pristine surface is exposed, the APXS, mini-TES. and
X-ray diffraction instruments can be employed to determine the mineralogy of samples not immediately exposed to
the Venusian atmosphere. Adaptation of the Rock Abrasion Tool to operation on Venus requires use of high-
temperature motors; an abrasion and coring tool for Venus is currently being developed,33 and a drill to has been
developed and demonstrated in operation on the surface of Venus by previous Russian missions.5
Imaging investigations are also important. A Microscopic Imager (MI)34 will be used to take close-up, high-
resolution images of rocks and surface soil. As it is placed on the rovers arm, used in conjunction with the RAT, the
MI will have the capability to take images of subsurface samples as well. Close up images of the Venusian surface
will be useful for studying the microstructure of rocks and soil. The Panoramic Camera, or PanCam for short, will
take high-resolution panoramic images of the surface.35 Images taken by PanCam would be useful in identifying
potentially interesting sampling sites, while the Navigation Cameras (“NavCams”)36 will take wider field-of-view
images to be used to direct the rover driving. Images provided from NavCam as well as PanCam will also provide
data for investigative studies of surface morphology, rock and soil distribution, as well as the general surface
geology. A calibration target will also be placed on the surface of the rover in view of the cameras, to provide a
reference for the cameras to calibrate images to the Venus illumination spectrum, so that the data taken on Venus
can be compared to data taken on Earth. Finally, the radar reflector is an unpowered instrument that will be used to
allow the rover to be located, either from a radar in an orbiting satellite, or directly from Earth.
V. Turbine-Powered Rover Detailed Design
A. Mission Requirements
To this date, spacecraft that have been sent to Venus include orbiters, atmospheric probes, stationary landers, and
balloons, but a rover has yet to be sent to explore Venus. The goal of this project is to analyze a conceptual design
for a rover to be sent to, and survive, the extreme conditions of the Venus surface. Due to these extreme surface
conditions, the longest a lander or probe has ever lasted is the Venera 13 for 127 minutes. The short mission times
mean that not much has been able to be studied on the surface first hand. This mission is designed to verify
assumptions based off the small amounts of data gathered from previous probe or lander missions, as well as
uncover entirely new data. Though the past probes to reach the surface of Venus have made advances over what was
known before them, a rover would be next level of discovery for Venus. Not only would one spot be able to be
studied, but several meters of area surrounding the landing site.
It is possible that the top layers of soil and outside of rocks are affected by the chemicals in the atmosphere. By
studying the lower layers of soil and the insides of rocks, the rover will be able to study samples that have been
untouched by the Venusian atmosphere for hundreds, or potentially even thousands of years. This will probe the
geological history of Venus, and determine the state of alteration of the mineralogy due to surface/atmospheric
interaction, and possible even shed light on the intriguing question of whether Venus ever had water on its surface,
and when (or if) the global climate had altered to its current state as a planet of extreme surface conditions.
B. Concept of Operations
Atmospheric entry and descent through the Venus atmosphere have been previously done by NASA with the
Pioneer Venus mission atmospheric probes.37 This mission assumes planetary entry will be performed with a direct
atmospheric entry using a 4.5 diameter aeroshell containing a heat shield on the bottom and a parachute system in
American Institute of Aeronautics and Astronautics
the top compartment. Upon atmospheric entry and deceleration, the heat shield will drop and the spacecraft will
slow down through the deployment of a drogue parachute followed by another high-temperature parachute.
The rover is assumed to land directly on its wheels, similar to the design in a previous study;8 however, landing
analysis or simulations were not conducted to validate the feasibility of the suspension system’s ability to absorb the
shock upon landing. There is no “typical” surface terrain to select on Venus; its diverse surface features include,
“mountain ranges, craters, continent-spanning sinuous hills, and chaotic terrain.” However, it is expected that a
highly sloped or extremely rugged landing site can be avoided and that the terrain will be relatively flat upon
landing. Surface roughness may be estimated from images obtained by the Russian Venera landers,38 as shown in
Fig. 9.
Figure 9. The surface of Venus, as viewed from Venera-9 (top) and Venera-13 (bottom) landers
The Venusian solar day lasts approximately 116.75 Earth days,39 so about 58 days of sunlight can be achieved
per day. Although the rover does not require sunlight for operation, since it is wind and not solar powered,
illumination is required for vision, and hence the mission will be designed to operate only during the daylit portion
of the Venus day. The mission duration was assumed to be 55 days, during with time all scientific operation and
data transmission back to Earth is to be accomplished. Under worst-case expected conditions of 0.3 m/s wind
speeds, the rover will need to charge for approximately 17 days between science runs, enabling for a total of 4
science runs. Average-case conditions of 0.6 m/s wind speeds enables for 19 mission science runs with two days of
charging time in between each run.
C. Wind Turbine Detailed Design
Initial analysis assumed that the rotor and generator would both operate at their maximum efficiencies;
however, because of the uncertainty regarding Venus surface conditions as well as some variation in wind speed
being likely, this is unworkable without the use of a variable gear ratio or voltage control of the generator. Both of
these techniques would require significant addition of moving parts and therefore complexity to the rover, which
would increase the risk of mission failure. To avoid this risk, three different generators will be used, each of which
will have a fixed gear ratio and voltage. Relationships between torque, RPM, and efficiency are based on fixed gear,
constant voltage assumptions40 and values for the high-temperature motor25 and can be seen in Fig. 10.
By switching between these generators, the rover will be able to maintain a tip speed ratio, torque, and RPM,
which will keep both the rotor and generator within acceptable operating limits over the required range of wind
American Institute of Aeronautics and Astronautics
Figure 10. RPM and Efficiency as Functions of Torque for a Constant Voltage Generator
Figure 11. Analysis of efficiency, power stored, tip speed ratio, and time to store energy for Generator #1 (low wind
American Institute of Aeronautics and Astronautics
Figure 12: Analysis of efficiency, power stored, tip speed ratio, and time to store energy for Generator #2
(intermediate wind speed)
Figure 13: Analysis of efficiency, power stored, tip speed ratio, and time to store energy for Generator #3 (high wind
American Institute of Aeronautics and Astronautics
VI. Rover Mechanical and Subsystem Design
A. Four-Wheel vs. Six-Wheel Design
Trade studies were conducted to determine the most feasible design for the rover body configuration. The
ability of the rover’s mobility system to traverse obstacles and its steering mechanism are major elements that
characterize the rover. Two types of suspension systems in particular were investigated for this mission: four-wheel
suspension and six-wheel rocker-bogie suspension systems.
Four-wheeled suspension systems use differential steering to change direction and require few motors for
actuation. The rocker-bogie suspension systems consist of two links, a main rocker, and a forward bogie on each
side, as illustrated in Fig. 14 (right). A wheel and steering mechanism is attached to one end of the main rocker
while the opposite end is connected to the forward bogie through a passive pivot joint. Weight is distributed on the
wheels by defining rocker and bogie lengths as well as pivot joint positions.41
Rovers capable of surmounting large obstacles in comparison to wheel size have a high degree of mobility.
Enough traction is required from the rear wheels to thrust the forward wheels with enough force to overcome an
obstacle. Four-wheeled rovers are typically incapable of traversing obstacles larger than the wheel radius due to lack
of traction while six-wheeled rovers are able to surmount these obstacles head-on because the extra wheels provide
greater traction and reduce the normal force on each wheel. Rocker-Bogie suspension systems can also perform
multiple types of steering (Ackerman, crabbing, differential, and zero radius) for greater mobility.41
Although the limited amount of traction is an issue for a four-wheeled rover design, the rover is still able to
overcome obstacles if the obstacle is approached at an angle and traversed one wheel at a time. This enables the
four-wheel design to have similar capabilities to the six-wheel design but with fewer control system requirements,
less suspension mass, and less actuation motors, which greatly reduces the weight and complexity of the system and
fits better within the scope of a Discovery-class mission. Furthermore, the rocker-bogie suspension system carries
the risk of jamming an obstacle between the tandem wheels of the bogie.
Figure 14. Four-Wheeled rover (left) and Six-wheeled Sojourner rover with rocker-bogie suspension (right)
B. Wheel Sizing and Drive Train Configuration
The diameter of the wheel is proportional to the size of the obstacle, and for a four-wheeled vehicle, it can be
estimated that the rover can overcome an obstacle roughly 18% of its wheel diameter. If an average obstacle size of
15 centimeters tall is assumed on the surface of Venus, the minimum wheel diameter required to traverse these
obstacles is approximately 0.833 meters.
Two different drive train configurations were investigated for this concept: a dual-output angle drive and a
standard four-wheel drive, as shown in Fig. 15. The dual-angle output drive concept is simpler and uses only two
motors for mobility, whereas the standard four-wheel drive would have a motor to power each wheel. However, the
simpler drive-train configuration can only accommodate one mode of steering (skid steering)41 and therefore not
selected for the design.
American Institute of Aeronautics and Astronautics
Figure 15. Dual-Output angle drive (left, courtesy University of Oklahoma) and standard four-wheel drive (right)
C. Rover Dimensions
Figures 16 and 17 shows the dimensions of the conceptual rover, which has a base width of 1.5 meters, a length
of 2 meters and a height of 2.75 meters. The relatively small size enables the rover to fit into a designed aeroshell
3.35 meters high and 4.5 meters in diameter without folding, as shown in Fig. 17, which simplifies the design and
avoids the need for complex folding mechanisms. The 4.5 meter diameter aeroshell is based on the Pioneer-Venus
atmospheric-entry aeroshell;37 the bottom of the aeroshell is heat shield, and the top compartment will store the
parachute system (not shown). Detailed analysis of aeroshell packing and entry, descent, and landing analysis was
not conducted in this study.
Figure 16. Dimensioned Rover (Side View)
American Institute of Aeronautics and Astronautics
Figure 17. Dimensioned Rover (Top View)
Figure 18. Rover fit in the Pioneer-Venus Large Probe aeroshell: Side View (Left) and Top View (Right)
D. Communications Design
The first step for the communications system was a trade study to decide between communication via an orbiting
relay satellite to connect to Earth, or a direct to Earth transmission. Although use of a relay increases the mission
cost by adding a second, orbiting, spacecraft, the antenna size and power required for a direct-to-Earth data link was
prohibitive. To minimize the transmission power required, a design in which the rover communicates through an
orbiting satellite was chosen to relay the data to Earth.
To determine the optimum orbiter altitude, the viewing angle from the center of Venus is calculated first. With
an assumed viewing angle from the surface of 45°, the orbital angle from the center of Venus, γ, is:
!!! (11)
American Institute of Aeronautics and Astronautics
Figure 19. Angle definitions:
viewing angle (from the surface)
and orbital angle (from center of
where h is the height from the surface, and the radius of Venus R is 6051.8
km. The range of orbital altitude considered ranged from 200 km above the
surface, barely above the Venusian atmosphere, to 10,000 km above the
surface. As the altitude of the relay satellite increased, the viewing angle from
the center of the Venus (and hence the fraction of the orbit that the relay is in
view) increased accordingly, as shown in Fig. 19. The final calculation used
the fraction of the orbit to calculate and find the highest fraction of power,
including both the view angle and the 1/r2 power law, to find the altitude at
which the highest bit rate to transfer data to and from Earth is achieved. The
analysis showed that that the highest fraction of power received by the orbiter
occurs with the lowest Venus orbit. Hence to get the highest amount of bits in
a given period of time, the lowest Venus orbit is optimal.
The orbital speed as a function of communication orbiter’s altitude is:
!!! (12)
is Venus’ standard gravitational parameter, 324,859 km3/s2. The
orbiting velocity was then used to find the overhead time, in which the
satellite was within the 45° viewing angle. The time it took to take one full
orbit around Venus was found using Kepler’s law:
! (13)
The amount of time the orbiter is in view of the lander (within 45° of the zenith) is shown in Fig. 20.
Figure 19. Bit Rate as a Function of Orbiting Satellite Height6
After finding the total bits/measurement for each instrument, the numbers of bits/measurement were totaled. This
number was then used in conjunction with the overhead time to find the bit rate. For this part in the project, it was
assumed that each instrument would only run once, and that the total number of bits would be able to be transferred
to the orbiting satellite in one overhead pass. This way, the lowest bit rate per single overhead pass would be able to
be found. In the most strained, basic scenario, each instrument would be able to run at least once and be able to
transfer all of the data back to Earth in one overhead pass. These bit rates will inevitably change, depending on the
amount of power designated to data transfer. It will also change due to the fact that the data coming from some
instruments will require more frequent measurements than others. The NavCam, for example, will need to send a
great deal of data back to Earth, to allow navigation to support driving. Other instruments, such as the CheMIN will
need to send only one measurement back to Earth at a time. The frequency at which each instrument will take
measurements has not yet been determined.
6 Calculated using total number of bits/measurement.
0" 100000" 200000" 300000" 400000" 500000" 600000" 700000"
American Institute of Aeronautics and Astronautics
Figure 20. Satellite Overhead Time in Relation to Orbiting Height
E. Radio Subsystem Design
The radio subsystem design requires a trade-off between the efficiency of operation at high temperature, the
radio opacity of the Venus atmosphere, and the complexity of tracking.
A solid-state radio system operating at a frequency of 500 MHz was chosen. Despite Venus’s thick and opaque
atmosphere, a frequency of 500 MHz is able to penetrate through the atmosphere, letting the rover connect to the
orbiting satellite and send data back to Earth.
The transmission frequency was chosen to be one at which silicon-carbide power amplifiers have been
demonstrated, in order to allow a fully solid-state transmitter operating at Venus ambient. NASA has successfully
tested a differential oscillator operating at 500 MHz at 475°C,42 a higher temperature than the surface of Venus,
which demonstrates that the main power amplifier of the communications system can be designed to operate at the
required temperatures.
The opacity of the Venus atmosphere to radio waves is a function of wavelength. Radar measurements show that
the opacity in the microwave to VHF region can be modeled as:43
α = (3.8/λ)2 (14)
where α is the absorption, and λ the wavelength in cm. At our target frequency of 500 MHz (λ =60 cm), the
absorption of the radio signal by the atmosphere is too small to be significant. The chosen frequency lies between
those used by the Russian Venera surface-to-relay communications, 122.8 and 138.6 MHz, and the Pioneer
atmospheric probes transmission frequency, 2.3 GHz,44 two previous missions which both successfully
communicated from the surface of Venus to spacecraft overhead.
Omnidirectional antennas do not require pointing, but since they transmit in all directions, only a small fraction
of the energy radiated is directed toward the receiver. An antenna with higher directivity (i.e., a high gain antenna)
allows more of the transmitted energy to be received by the relay satellite and hence reduces the energy required per
bit communicated, but puts constraints on the wavelengths or else requires larger antenna size. A high antenna gain
also requires that the antenna be accurately pointed at the receiver. Antenna pointing adds to the complexity in the
system, requiring either mechanical components (gimbal, motor) or a phased-array for electronic steering, as well as
added computational complexity of understanding the rover orientation and tilt and calculating the satellite location
relative to the rover. The three-element Yagi antenna chosen is a compromise between the simplicity of an
omnidirectional antenna and the complexity of a dish. It provides a moderate gain of about 7.5 dB (compared to a
dipole). As a result, it will require pointing. To mitigate the complexity of tracking, it was assumed that four Yagi
antennas are mounted on the rover, and the transmitter output is switched to the appropriate antenna. The rover
orientation may also be adjusted to optimally place the antenna pattern over the orbiter track.
VII. Conclusion
The Curiosity mission to Mars has reminded the public of the value of rovers on extraterrestrial planets, and it is
time to extend this capability to another planet, Venus. Venus is of scientific interest at least as great as the interest
in Mars, and, the more can be found out about Venus by use of a rover mission, while the public is still excited and
willing to support extraterrestrial planetary rovers.
0" 500" 1000" 1500" 2000" 2500" 3000" 3500" 4000"
American Institute of Aeronautics and Astronautics
The benefit of having a rover on Venus is the fact that it can conduct science in more than one location, rather
than being fixed at the landing spot. This, with the use of high temperature silicon-carbide electronics, may be
exactly what is needed to find out the geological history and present geology and mineralogy of Venus. While it is
difficult to design a rover to survive the surface conditions of Venus, that just means that this mission is that much
more important. If there is no challenge, and nothing new to learn, then there would be no point to science at all.
Venus has both of these components at large, making it one of the most scientifically interesting planets in our solar
The student researchers on this project enjoyed the support of the NASA Space Academy 2012 program. We
would like to thank NASA Glenn artist Terence Condrich for his artist’s conception of our rover, Dr. Kankam and
Bernice Beznoska of NASA Glenn for their work hosting the NASA Space Academy, and our respective California
and Maryland Space Grant Consortiums for their funding this summer.
1Loders, K., and Fegley Jr., B., The Planetary Scientist’s Companion, Oxford, 1998, pp. 108-124.
2 Neudeck P. G., Okojie R. S. , and Chen, L.-Y., “High-Temperature Electronics- A Role for Wide Bandgap
Semiconductors,” Proceedings of the IEEE, Vol. 90, No. 6, June 2002, pp. 1065-1076.
3 Chen, L.-Y., Hunter, G. W., and Neudeck, P. G., "Silicon Carbide Die Attach Scheme for 500°C Operation,"
Proc. Materials Research Soc. Symposium 2000, Vol. 622, No. 1, Cambridge University Press, 2000, pp.
4 Hunter, G. W., Okojie, R. S., Neudeck, P. G., Beheim, G. M., Ponchak, G. E., Fralick, G., Wrbanek, J.,
Kraskowski, M., Spry, D., and Chen, L. Y., "High Temperature Electronics, Communications, and
Supporting Technologies for Venus Missions," Fourth Annual International Planetary Probe Workshop,
Pasadena, CA, June 2006.
5 Kolawa, E., Extreme Environments Technologies for Future Space Science Missions, JPL D-32832, NASA,
Sept. 19, 2007.
6 Saunders, R. S., Spear, A. J., Allin, P. C., Austin, R. S., Berman, A. L., Chandlee, R. C., ... and Wall, S. D.,
“Magellan Mission Summary,” Journal of Geophysical Research, 97 (E8), 1992, 13067-13.
7 Landis, G. A., “Robotic Exploration of the Surface and Atmosphere of Venus,” paper IAC-04-Q.2.A.08, Acta
Astronautica, Vol. 59, No. 7, October 2006, pp. 517-580.
8 Landis, G. A., Dyson, R., Oleson, S. J., Warner, J. D., Colozza, A. J., and Schmitz, P. C., "Venus Rover Design
Study," paper AIAA-2011-7268, AIAA Space 2011 Conference & Exposition, Long Beach CA, Sept. 26-29,
9 Bennett, G. L., Lombardo, J. J., Hemler, R. J., and Peterson, J. R., “The General-purpose Heat Source
Radioisotope Thermoelectric Generator - Power for the Galileo and Ulysses Missions,” Proc. Intersociety
Energy Conversion Engineering Conference (IECEC) '86, 1986, pp. 1999-2011.
10 Wong, W. A., Wood, J. G., and Wilson, K., “Advanced Stirling Convertor (ASC)--From Technology
Development to Future Flight Product,” Space Technology and Applications International Forum (STAIF
2008), Albuquerque, NM, February 10-14 2008; NASA/TM-2008-215282, 2008.
11 Dyson, R. W., and Bruder, G. A., “Progress Towards the Development of a Long-Lived Venus Lander Duplex
System,AIAA Paper 2010-6917, 8th AIAA International Energy Conversion Engineering Conference
(IECEC), Nashville, TN, July 2528, 2010; NASA/TM-2011-217018, 2011.
12 Lafleur, J. D., "Nuclear Power Systems for Spacecraft," IEEE Transactions on Aerospace and Electronic
Systems, Vol. 2, 1970, pp. 147-164.
13 Keldysh, M. V., “Venus Exploration with the Venera 9 and Venera 10 Spacecraft,” Icarus, 30 (4), 1977, pp.
14 Ksanfomalti, L., Goroshkova, N., and Khondyrev, V., Wind Velocity at the Venus Surface According to
Acoustic Measurements,” Kosmicheskie Issledovaniia, 21, Mar-April 1983, pp. 218-224. In English:
American Institute of Aeronautics and Astronautics
15 Landis, G. A., "A Landsailing Rover for Venus Mobility," Journal of the British Interplanetary Society, to be
published (2013).
16 Kimball, J., Physics of Sailing, Taylor and Francis Group, Boca Raton, FL, 2010. 978-1-4200-7376-8.
17 Marchaj, C. A., Aero-Hydrodynamics of Sailing, 3rd edition, Tiller Publishing, Easton, MD, 2000. ISBN-13:
18 Landis, G. A. and Vo, T., "Photovoltaic Performance in the Venus Environment," 34th IEEE Photovoltaic
Specialists Conference, Philadelphia PA, 7-12 June 2009; in updated form as Landis, G. A., and Haag, E.,
“Analysis of Solar Cell Efficiency for Venus Atmosphere and Surface Missions” AIAA 11th International
Energy Conversion Engineering Conference, San Jose CA, July 2013.
19 Ji, J., Narine, R., Kumar, N., Singh, S., and Gorevan, S., "High Temperature Mechanisms for Venus
Exploration," 37th COSPAR Scientific Assembly, Vol. 37, 2008, p. 1370.
20 Harrison, R., and Landis, G. A., "Batteries for Venus Surface Operation," Paper AIAA-2008-5796, Journal of
Propulsion and Power, Vol. 26, Number 4, July/Aug 2010, pp., 649-654.
21 Park, J., The Wind Power Book, Chesire, Palo Alto, CA, 1981.
22 Ragheb, M., and Ragheb, A. M., "Wind Turbines Theory- The Betz Equation and Optimal Rotor Tip Speed
Ratio," in R. Carriveau, Fundamental and Advanced Topics in Wind Power, 2011, pp. 19-37.
23 Livingston, T., "Space Frame Towers," California Wind Energy Collaborative, Wind Tower Composites,
24 Griffin, D. A., Blade System Design Studies, Volume II: Preliminary blade designs and recommended test
matrix; SAND2004-0073, United States Department of Energy, 2004.
25 Honeybee Robotics, “Data Sheet: High Temperature Motor / Extreme Environment Actuator,”
26 Gómez-Elvira, J., Castañer, L., Lepinette, A., Moreno, J., Polko, J., Sebastián, E., Torres, J., Zorzano, M. T.,
and the REMS Team, REMS, an Instrument for Mars Science Laboratory Rover,” Lunar and Planetary
Institute Science Conference Abstracts, Vol. 40, March 2009, p. 1540.
27 Rieder, R., et al., "The New Athena Alpha Particle X-ray Spectrometer for the Mars Exploration Rovers,"
Journal of Geophysical Research, Vol. 108, November 11, 2003, p. 13.
28 Shanmugam, M., Acharya, Y. B., Goyal, S. K., and Murty, S. V. S., "Alpha Particle X-Ray Spectrometer
(APXS) On-Board Chandrayaan-2 Rover," Lunar and Planetary Institute Science Conference Abstracts, Vol.
42, March 2011, p. 1232.
29 Gellert, R., Campbell, J. L., King, P. L., Leshin, L. A., Lugmair, G. W., Spray, J. G., ... and Yen, A. S., "The
Alpha-Particle-X-Ray Spectrometer (APXS) for the Mars Science Laboratory (MSL) Rover Mission," 40th
Lunar and Planetary Science Conference, Houston, TX, March 2009. Lunar and Planetary Institute, Vol.
30 Christensen, P. R., et al., "The Miniature Thermal Emission Spectrometer for the Mars Exploration Rovers,"
Journal of Geophysical Research, Vol. 108, December 24, 2003, p. 23.
31 Blake, D., et. al., "Characterization and Calibration of the CheMin Mineralogical Instrument on Mars Science
Laboratory," Space Science Reviews, Vol. 170, No. 1-4, 2012 (DOI: 10.1007/s11214-012-9905-1), pp. 341-
32 Gorevan, S. P., Myrick, T., Davis, K., Chau, J. J., Bartlett, P., Mukherjee, S., and Richter, L., "Rock Abrasion
Tool: Mars Exploration Rover Mission," Journal of Geophysical Research, Vol. 108 (E12), 2003, 8068.
33 Ji, J, “High Temperature Mechanisms,” Short Course on Extreme Environment Technology, 6th International
Planetary Probe Workshop, Atlanta GA, June 21-22 2008.
34 Herkenhoff, K. E., et al., "Athena Microscopic Imager investigation," Journal of Geophysical Research, Vol.
108, 2003.
35 Bell III, J. F., et al., "Mars Exploration Rover Athena Panoramic Camera (Pancam) investigation," Journal of
Geophysical Research, 10 8 (E12), 2003, 8063.
36 Maki, J. N., et al., "Mars Exploration Rover Engineering Cameras," Journal of Geophysical Research, Vol.
108, American Geophysical Union, 2003.
37 Fimmel, R. O., Colin, L. and Burgess, E., Pioneer Venus, NASA report SP-461, 1983.
38 Garvin, J., Head, J., Zuber, M., and Helfenstein, P., “Venus: the Nature of the Surface from Venera
Panoramas,” J. Geophys. Res., 89, B5, May 10 1984, pp. 3381-3399.
39 Bond, P., Exploring the Solar System, John Wiley & Sons, Hoboken, NJ, 2012.
40 Gottlieb, I., Electric Motors and Control Techniques, McGraw-Hill, 1994.
American Institute of Aeronautics and Astronautics
41 Roman, M. J., Design and Analysis of a Four-Wheeled Planetary Rover. University of Oklahoma, Norman,
OK, 2005.
42 Hunter, G., et al., "Development of High Temperature Wireless Sensor Technology Based on Silicon Carbide
Electronics," ECS Transactions, 33(8), The Electrochemical Society, 2010, pp. 269-281.
43 Muhleman, D. O., “Microwave Opacity of the Venus Atmosphere,” Astronomical Journal, Vol. 74, No. 1, 57-
68, February 1969 (DOI 10.1086/110776).
44 Smith, J. R., and Ramos, R., “Data Acquisition for Measuring the Wind on Venus from Pioneer Venus,”
Telecommunications and Data Acquisition Progress Report 42-57, IEEE Transactions on Geoscience and
Remote Sensing, vol. GE-18, No. 1, January 1980, pp. 126-130.
... Other power systems have been proposed for the Venus surface. Wind power systems have attracted some interest [32][33][34]. One proposed wind-powered lander is shown in Fig. 4. The surface winds of Venus were measured on four of the Soviet Venera missions, showing speeds ranging from 0.3 m/s (Venera 14) to a 1.3 m/s (maximum measured on Venera 10) [35]. ...
... A 3D-printed model of a proposed small wind-powered lander for Venus [32]. ...
Future missions to Venus will require electrical power, but providing power systems that work in the high temperature environment of the surface of Venus is difficult. Power system choices include solar power from photovoltaic arrays, batteries, radioisotope power systems, and wind. The current state of power technology for operation on the Venus surface sources is surveyed and assessed.
... A rover massing 1059 kg (1.99 m x 0.33 m x 2 m) with a thermal control system has been proposed to operate at 500 degrees [4]. A much smaller wind powered rover of 70 kg (2.75 m x 0.33 m x 2 m) was proposed with studies of potential power systems, communication and radio systems [5]. The wind speeds required [6]. ...
Venus is among the most enigmatic and interesting places to explore in the solar system. However, the surface of Venus is a very hostile, rocky environment with extreme temperatures, pressures, and chemical corrosivity. A planetary rover to explore the surface would be scientifically valuable, but must use unconventional methods in place of traditional robotic control and mobility. This study proposes that a tensegrity structure can provide adaptivity and control in place of a traditional mechanism and electronic controls for mobility on the surface of Venus and in other extreme environments. Tensegrity structures are light and compliant, being constructed from simple repeating rigid and flexible members and stabilized only by tension, drawing inspiration from biology and geometry, and are suitable for folding, deployment, and adaptability to terrain. They can also utilize properties of smart materials and geometry to achieve prescribed movements. Based on the needs of scientific exploration, a simple tensegrity rover can provide mobility and robustness to terrain and environmental conditions, and can be powered by environmental sources such as wind. A wide variety of tensegrity structures are possible, and some initial concepts suitable for volatile and complex environments are proposed here.
... Given the electronics protection driven limitations of prior Venus lander designs, it has been recognized for some time that long duration Venus lander missions would require a complete suite of lander operations electronics and sensors functioning for long-duration in, and without protection from, the extreme environment. As a variety of wide bandgap semiconductor (SiC and III-Nitride) transistors and circuits have been reported to operate at T ≥ 460 °C over the last two decades, these progressing wide bandgap technologies have been pondered as candidates for use in Venus surface exploration missions [12][13][14]. The fact that wide bandgap ICs are far less complex/developed/capable than modern silicon ICs is arguably a perceived technical barrier. ...
Prolonged Venus surface missions (lasting months instead of hours) have proven infeasible to date in the absence of a complete suite of electronics able to function for such durations without protection from the planet’s extreme conditions of 460 ∘C, 9.3 MPa ( 92 Earth atmospheres) chemically reactive environment. Here we report testing data from a successful twomonth (60-day) operational demonstration of two 175-transistor 4H-SiC junction field effect transistor (JFET) semiconductor integrated circuits (ICs) directly exposed (no cooling and no protective chip packaging) to a high-fidelity physical and chemical reproduction of Venus surface atmospheric conditions in a test chamber. These results extend the longest reported duration of electronics operation in Venus surface atmospheric conditions almost 3-fold and were accomplished using prototype SiC JFET chips of more than 7-fold increased complexity. The demonstrated advancement marks a significant step towards realization of electronics with sufficient complexity and durability for implementing robotic landers capable of returning months of scientific data from the surface of Venus.
... The use of wind energy for vehicle propulsion has also been investigated by NASA in collaboration with JPL for planetary exploration purposes [14,15]. Solutions using winddriven inflatable spherical robots have also been proposed for polar expedition [16]. ...
This paper presents a study on the dynamic modelling of a land-yacht, i.e. a ground vehicle that is propelled by wind energy through the use of a vertical airfoil. First, a non-linear dynamic model of the land-yacht motion is derived using a compact matrix notation. Then, an introduction to the study of the performance and handling characteristics is presented. It is considered the vehicle response to input commands, i.e. steering to follow the desired course and adjusting the sail angle according to environmental conditions, that is, wind intensity and direction. The model demonstrates the performance in terms of maximum longitudinal speed and the effects on handling behaviour of the major vehicle design and operational parameters, including location of the centre of gravity and centre of effort, and forward speed, and it leads to conclusions of practical significance concerning directional control and stability.
... This work follows onto two previous studies of wind-powered missions to Venus. Use of wind power on Venus was first proposed in an initial 2012 study by NASA Space Academy students at NASA Glenn, who looked at the possible use of a wind turbine as the power source for a small Venus rover 19 . This was followed by a NASA Innovative Advanced Concepts (NIAC) study that examined the feasibility of a sail powered rover on Venus 20 . ...
... For example, a speed of 203.1 km/h was recorded for a land-yacht in 2009 when wind speeds were fluctuating between 48 and 80 km/h [9]. The use of wind-propelled vehicles has also been proposed for planetary exploration by NASA [10], [11]. JPL as well developed wind-driven inflatable spherical robots for polar expedition [12]. ...
Conference Paper
This paper deals with the study of a land-yacht, that is a ground vehicle propelled by wind energy. There is a large interest in exploring alternative source of energy for propulsion and wind energy could be a feasible solution being totally green, available and free. The idea envisaged by a land-yacht is that of using one or several flexible or rigid vertical wing-sails to produce a thrust-force, which can eventually generate a higher travel velocity than its prevailing wind. A model of a three-wheel land-yacht is presented capturing the main dynamic and aerodynamic aspects of the system behaviour. Simulations are included showing how environment conditions, i.e. wind intensity and direction, influence the vehicle response and performance. In view of a robotic embodiment of the vehicle, a controller of the sail trim angle and front wheel steer angle is also discussed for autonomous navigation. Copyright © 2016 by ASME Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
Full-text available
The performance of Al0.3Ga0.7As/InP/Ge triple-junction solar cells (TJSC) at the geosynchronous orbit of Venus had been simulated in this paper by assuming that the solar cells were put on a hypothetical Venus orbiter space station. The incoming solar radiation on TJSC was calculated by a blackbody radiation formula, while PC1D program simulated the electrical output performance. The results show that the incoming solar intensity at the geosynchronous orbit of Venus is 3000 W/m2, while the maximum solar cell efficiency achieved is 38.94%. Considering a similar area of the solar panel as the International Space Station (about 2500 m2), the amount of electricity produced by Venus orbiter space station at the geosynchronous orbit of Venus is 2.92 MW, which is plenty of energy to power the space station for long-term exploration and intensive research on Venus.
This paper presents the results of a thermodynamic analysis of a two-stage cascaded vapor compression refrigeration cycle developed for high-temperature high-pressure applications, such as the one encountered in Venus surface lander missions. The bottoming cycle uses ammonia, whereas the topping cycle uses fatty acid methyl ester methyl linoleate (FAME-MLL) as the working fluid. The working fluid FAME-MLL is selected for its critical point temperature of 526°C, which is greater than the local Venus atmospheric temperature of 465°C, thus providing a temperature potential to reject heat to the Venus environment. The FAME-MLL cycle employs an ejector in order to alleviate overloading the compressor. The paper presents the thermodynamic model of the system followed by predictions of system performance in terms of ejector flow rate, condenser temperature, evaporator temperature, and compressor efficiency. The results herein show that, over the ranges of ejector entrainment ratios of 2<w<3 and compressor efficiencies of 70%<ηc<80%, the system coefficient of performance (COP) falls within the range of 0.7<COP<0.8. The main objective of this research is to provide an active thermal control system architecture that will maintain a payload on Venus rejecting 100 W at 100°C for an extended period of days or weeks. Thus, the overall longevity of the mission is deemed more important than a system with a large COP value. Thus, the conceptual design provided herein is seen to meet the primary objectives.
“Venus, the “greenhouse planet”, is scientifically fascinating place.” (Landis G, NASA). Based on the fact of growing interest in Venus exploration, backed by the US National Academies of Sciences’ listing of the Earth’s “hellish twin” as one of the mission destinations with high priority, exploration mission architectures for Venus are expected to respond to operational expectations that are higher than the early period of Venus missions. High profile missions point out the need for more capable, more flexible, better designs.
Conference Paper
Full-text available
The surface of Venus is a hostile environment, with a surface temperature averaging 452°C, and atmospheric pressure of 92 bars of carbon dioxide. Nevertheless, exploration of the surface of Venus is of scientific interest. Technologies currently being developed at NASA bring the operation of robots on Venus into the range of feasibility. These include high-temperature electronics; radioisotope power systems that operate at Venus temperatures; Stirling-based power and cooling systems to keep mission components within temperature constraints; high-temperature, corrosion-resistant materials; and hightemperature sensors, motors, actuators, and bearings. This paper presents the results of a design study for a Venus rover, with the goal of surface exploration capability that is comparable to that of Mars rover missions. The most critical portion of the design is the power and cooling system required for operation at Venus, and this analysis will comprise most of the work presented. The thermal design requires operation at an external temperature as high as 500°C. To minimize external heat flow into the electronics enclosure (and also to provide maximum structural strength against external pressure) the electronics enclosure is assumed to be spherical shell. A radioisotope Stirling Duplex engine provides electrical power and 2-stage cooling. In order to minimize heat leaks, the number of penetrations to the thermal enclosure was minimized. Optical instruments were assumed to operate through sapphire windows, and all the components that could be operated in the high-temperature Venus environment were located outside the enclosure. Total rover design mass (including cruise and EDL system) is 872 kg without growth, and 1059 kg with mass growth allowance included; this is easily within the launch capability of an expendable launch vehicle. There are no apparent showstoppers to the design of a rover capable of operation on the Venus surface, although some of the technologies will still need development to bring them to flight readiness.
Full-text available
The Athena science payload on the Mars Exploration Rovers (MER) includes the Microscopic Imager (MI). The MI is a fixed-focus camera mounted on the end of an extendable instrument arm, the Instrument Deployment Device (IDD). The MI was designed to acquire images at a spatial resolution of 30 microns/pixel over a broad spectral range (400-700 nm). The MI uses the same electronics design as the other MER cameras but has optics that yield a field of view of 31 × 31 mm across a 1024 × 1024 pixel CCD image. The MI acquires images using only solar or skylight illumination of the target surface. A contact sensor is used to place the MI slightly closer to the target surface than its best focus distance (about 66 mm), allowing concave surfaces to be imaged in good focus. Coarse focusing (~2 mm precision) is achieved by moving the IDD away from a rock target after the contact sensor has been activated. The MI optics are protected from the Martian environment by a retractable dust cover. The dust cover includes a Kapton window that is tinted orange to restrict the spectral bandpass to 500-700 nm, allowing color information to be obtained by taking images with the dust cover open and closed. MI data will be used to place other MER instrument data in context and to aid in petrologic and geologic interpretations of rocks and soils on Mars.
Full-text available
A principal goal of the Mars Science Laboratory (MSL) rover Curiosity is to identify and characterize past habitable environments on Mars. Determination of the mineralogical and chemical composition of Martian rocks and soils constrains their formation and alteration pathways, providing information on climate and habitability through time. The CheMin X-ray diffraction (XRD) and X-ray fluorescence (XRF) instrument on MSL will return accurate mineralogical identifications and quantitative phase abundances for scooped soil samples and drilled rock powders collected at Gale Crater during Curiosity’s 1-Marsyear nominal mission. The instrument has a Co X-ray source and a cooled charge-coupled device (CCD) detector arranged in transmission geometry with the sample. CheMin’s angular range of 5° to 50° 2θ with 13 that are contained in the sample. The CheMin XRD is equipped with internal chemical and mineralogical standards and 27 reusable sample cells with either Mylar® or Kapton® windows to accommodate acidic-to-basic environmental conditions. The CheMin flight model (FM) instrument will be calibrated utilizing analyses of common samples against a demonstrationmodel (DM) instrument and CheMin-like laboratory instruments. The samples include phyllosilicate and sulfate minerals that are expected at Gale crater on the basis of remote sensing observations.
Contents include: introduction; wind power systems; wind energy resources; wind machine fundamentals; wind machine design; building a wind power system; and wind power economics, legal and social issues.
Conference Paper
Smart Sensor Systems that can operate at high temperatures are required for a range of aerospace applications including propulsions systems. This paper discusses the development of a high temperature wireless system that includes a sensor, electronics, wireless communication, and power. In particular, a wireless pressure sensor was demonstrated at 300°C, with signal transmission over one meter distance and power derived from scavenged energy. The circuit had a nominal oscillation frequency of near 100 MHz and used a commercial SiC metal semiconductor field effect transistor (MESFET) together with metal-insulator-metal (MIM) capacitors and a thin film inductor/antenna. With the sensor and oscillator circuit at temperatures from 25 to 300°C, the oscillator frequency, detected at a distance of one meter, was found to vary repeatably as a function of pressure. This work is considered a foundation for the development of higher temperature Smart Sensor Systems for use in harsh environments.
NASA has begun the development of a combined Stirling cycle power and cooling system (duplex) to enable the long-lived surface exploration of Venus and other harsh environments in the solar system. The duplex system will operate from the heat provided by decaying radioisotope plutonium-238 or its substitute. Since the surface of Venus has a thick, hot, and corrosive atmosphere, it is a challenging proposition to maintain sensitive lander electronics under survivable conditions. This development effort requires the integration of: a radioisotope or fission heat source; heat pipes; high-temperature, corrosion-resistant material; multistage cooling; a novel free-displacer Stirling convertor for the lander; and a minimal vibration thermoacoustic Stirling convertor for the seismometer. The first year effort includes conceptual system design and control studies, materials development, and prototype hardware testing. A summary of these findings and test results is presented in this report.
Magellan started mapping the planet Venus on September 15, 1990, and after one cycle (one Venus day or 243 Earth days) had mapped 84% of the planet's surface. This returned an image data volume greater than all past planetary missions combined. Spacecraft problems were experienced in flight. Changes in operational procedures and reprogramming of onboard computers minimized the amount of mapping data lost. Magellan data processing is the largest planetary image-processing challenge to date. Compilation of global maps of tectonic and volcanic features, as well as impact craters and related phenomena and surface processes related to wind, weathering, and mass wasting, has begun. The Magellan project is now in an extended mission phase, with plans for additional cycles out to 1995. The Magellan project will fill in mapping gaps, obtain a global gravity data set between mid-September 1992 and May 1993, acquire images at different view angles, and look for changes on the surface from one cycle to another caused by surface activity such as volcanism, faulting, or wind activity.
The Miniature Thermal Emission Spectrometer (Mini-TES) will provide remote measurements of mineralogy and thermophysical properties of the scene surrounding the Mars Exploration Rovers and guide the rovers to key targets for detailed in situ measurements by other rover experiments. The specific scientific objectives of the Mini-TES investigation are to (1) determine the mineralogy of rocks and soils, (2) determine the thermophysical properties of selected soil patches, and (3) determine the temperature profile, dust and water-ice opacity, and water vapor abundance in the lower atmospheric boundary layer. The Mini-TES is a Fourier Transform Spectrometer covering the spectral range 5-29 μm (339.50 to 1997.06 cm-1) with a spectral sample interval of 9.99 cm-1. The Mini-TES telescope is a 6.35-cm-diameter Cassegrain telescope that feeds a flat-plate Michelson moving mirror mounted on a voice-coil motor assembly. A single deuterated triglycine sulfate (DTGS) uncooled pyroelectric detector with proven space heritage gives a spatial resolution of 20 mrad; an actuated field stop can reduce the field of view to 8 mrad. Mini-TES is mounted within the rover's Warm Electronics Box and views the terrain using its internal telescope looking up the hollow shaft of the Pancam Mast Assembly (PMA) to the fixed fold mirror and rotating elevation scan mirror in the PMA head located ~1.5 m above the ground. The PMA provides a full 360°of azimuth travel and views from 30° above the nominal horizon to 50° below. An interferogram is collected every two seconds and transmitted to the Rover computer, where the Fast Fourier Transform, spectral summing, lossless compression, and data formatting are performed prior to transmission to Earth. Radiometric calibration is provided by two calibration V-groove blackbody targets instrumented with platinum thermistor temperature sensors with absolute temperature calibration of +/-0.1°C. One calibration target is located inside the PMA head; the second is on the Rover deck. The Mini-TES temperature is expected to vary diurnally from -10 to +30°C, with most surface composition data collected at scene temperatures >270 K. For these conditions the radiometric precision for two-spectra summing is +/-1.8 × 10-8 W cm-2 sr-1/cm-1 between 450 and 1500 cm-1, increasing to ~4.2 × 10-8 W cm-2 sr-1/cm-1 at shorter (300 cm-1) and longer (1800 cm-1) wave numbers. The absolute radiance error will be <5 × 10-8 W cm-2 sr-1/cm-1, decreasing to ~1 × 10-8 W cm-2 sr-1/cm-1 over the wave number range where the scene temperature will be determined (1200-1600 cm-1). The worst-case sum of these random and systematic radiance errors corresponds to an absolute temperature error of ~0.4 K for a true surface temperature of 270 K and ~1.5 K for a surface at 180 K. The Mini-TES will be operated in a 20-mrad panorama mode and an 8-mrad targeted mode, producing two-dimensional rasters and three-dimensional hyperspectral image cubes of varying sizes. The overall Mini-TES envelope size is 23.5 × 16.3 × 15.5 cm, and the mass is 2.40 kg. The power consumption is 5.6 W average. The Mini-TES was developed by Arizona State University and Raytheon Santa Barbara Remote Sensing.
The surface of Venus is a location that is of great interest for future scientific exploration, but designing a rover that can move and conduct science operations on Venus is a difficult task. Electronic and materials technologies are available that could survive the furnace of Venus, but such a rover represents a challenging design problem. One approach to the problem is to make use of the features of the Venus environment, such as the thick atmosphere. A new approach for rover mobility is proposed, in which the rover motive force is produced by a sail. Such a Venus landsailing rover could be small and low powered, since the main power required for motion is generated by the wind, rather than by motors. Although the wind velocities on Venus are low, estimated at 0.6 ± 0.3 m/sec at the Venera landing sites, due to the high density of the atmosphere, sufficient force would be generated on a sail to allow good mobility for a lightweight rover.
The new APXS for the MSL Rover mission was successfully tested, calibrated and delivered to NASA/JPL. The data acquisition time compared to MER was decreased by about a factor of 3, allowing a full in-situ chemical analysis within ~3 hours at temperatures below ~-5C.