B.H. Wilcox

California Institute of Technology, Pasadena, CA, United States

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Publications (8)0 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: As we have previously reported [1–4], it may be possible to launch payloads into low-Earth orbit (LEO) at a per-kilogram cost that is one to two orders of magnitude lower than current launch systems. The capital investment required would be relatively small, comparable to a single large present-day launch. <sup>1 2</sup> An attractive payload would be large quantities of high-performance chemical rocket propellant (e.g. Liquid Oxygen/Liquid Hydrogen (LO 2 /LH 2 )) that would greatly facilitate, if not enable, extensive exploration of the moon, Mars, and beyond. The concept is to use small, mass-produced, two-stage, LO 2 /LH 2 , pressure-fed rockets (without pumps or other complex mechanisms). These small rockets can reach orbit with modest atmospheric drag losses because they are launched from very high altitude (e.g., 22 km). They would reach this altitude by being winched up a tether to a balloon that would be permanently stationed there. The drag losses on a rocket are strongly related to the ratio of the rocket launch mass to the mass of the atmospheric column that is displaced as the vehicle ascends from launch to orbit. By reducing the mass of this atmospheric column to a few percent of what it would be if launched from sea level, the mass of the rocket could be proportionately reduced while maintaining drag loss at an acceptably small level. The system concept is that one or more small rockets would be launched to rendezvous on every orbit of a propellant depot in LEO. There is only one orbital plane where a depot would pass over the launch site on every orbit - the equator. Fortunately, the U.S. has two small islands virtually on the equator in the mid-Pacific (Baker and Jarvis Islands). Launching one on every orbit, approximately 5,500 rockets would be launched every year, which is a manufacturing rate that would allow significantly reduced manufacturing costs, especially when combined with multi year production c- - ontracts, giving a projected propellant cost in LEO of $400/kg or less. This paper provides new analysis and discussion of a configuration for the payload modules to eliminate the need for propellant transfer on-orbit. Instead of being a “propellant depot”, they constitute a “propulsion depot”, where propulsion modules would be available, to be discarded after use. The key observation here is that the only way cryo-propellant can get to orbit is by already being in a tank with a rocket engine, and that careful system engineering could ensure that that same tank and engine would be useful to provide the needed rocket impulse for the final application. Long “arms” of these propulsion modules, docked side-by-side, could boost large payloads out of LEO for relatively low-cost human exploration of the solar system.
    Aerospace Conference, 2011 IEEE; 04/2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: As we have previously reported, it may be possible to launch payloads into low-Earth orbit (LEO) at a per-kilogram cost that is one to two orders of magnitude lower than current launch systems, using only a relatively small capital investment (comparable to a single large present-day launch). An attractive payload would be large quantities of high-performance chemical rocket propellant (e.g. LO2/LH2) that would greatly facilitate, if not enable, extensive exploration of the moon, Mars, and beyond. The concept is to use small, mass-produced, two-stage, LO2/LH2, pressure-fed rockets (e.g. without turbopumps, which increase performance but are costly). These small rockets could reach orbit with modest atmospheric drag losses because they are launched from very high altitude (e.g. 22 km). They reach this altitude by being winched up a tether to a balloon that is permanently stationed there. The drag losses on a rocket are strongly related to the ratio of the rocket launch mass to the mass of the atmospheric column that is displaced as the vehicle ascends from launch to orbit. By reducing the mass of this atmospheric column to a few percent of what it would be if launched from sea level, the mass of the rocket could be proportionately reduced while maintaining drag loss at an acceptably small level. The system concept is that one or more small rockets would be launched to rendezvous on every orbit of a propellant depot in LEO. There is only one orbital plane where a depot would pass over the launch site on every orbit - the equator. Fortunately, the U.S. has two small islands virtually on the equator in the mid-Pacific (Baker and Jarvis Islands). Launching one on every orbit, approximately 5,500 rockets would be launched every year, which is a manufacturing rate that allows significantly reduced manufacturing costs, especially when combined with multiyear production contracts, giving a projected propellant cost in LEO of $400/kg or less. The configuration of the proposed- - propellant depot and the manner in which the propellant would be utilized has already been reported. The launch processing facility (a small, modified container ship) and cable-car that moves the rocket on the tether have also been reported. This paper provides new analysis of the economics of low-cost propellant launch coupled with dry hardware re-use, and of the thermal control of the liquid hydrogen once on-orbit. One conclusion is that this approach enables an overall reduction in the cost-per-mission by as much as a factor of five as compared to current approaches for human exploration of the moon, Mars, and near-Earth asteroids.
    Aerospace Conference, 2010 IEEE; 04/2010
  • B.H. Wilcox
    [Show abstract] [Hide abstract]
    ABSTRACT: As part of the NASA Exploration Technology Development Program, the Jet Propulsion Laboratory is developing a vehicle called ATHLETE: the All-Terrain Hex-Limbed Extra-Terrestrial Explorer. Each vehicle is based on six wheels at the ends of six multi-degree-of-freedom limbs. Because each limb has enough degrees of freedom for use as a general-purpose leg, the wheels can be locked and used as feet to walk out of excessively soft or other extreme terrain. Since the vehicle has this alternative mode of traversing through or at least out of extreme terrain, the wheels and wheel actuators can be sized for nominal terrain. There are substantial mass savings in the wheel and wheel actuators associated with designing for nominal instead of extreme terrain. These mass savings are at least comparable-to or larger-than the extra mass associated with the articulated limbs. As a result, the entire mobility system, including wheels and limbs, can be lighter than a conventional all-terrain mobility chassis. A side benefit of this approach is that each limb has sufficient degrees-of-freedom to be used as a general-purpose manipulator (hence the name ¿limb¿ instead of ¿leg¿). Our prototype ATHLETE vehicles have quick-disconnect tool adapters on the limbs that allow tools to be drawn out of a ¿tool belt¿ and maneuvered by the limb. A power-take-off from the wheel actuates the tools, so that they can take advantage of the 1+ horsepower motor in each wheel to enable drilling, gripping or other power-tool functions.
    Aerospace Conference, 2010 IEEE; 04/2010
  • [Show abstract] [Hide abstract]
    ABSTRACT: As we have previously reported, it may be possible to launch payloads into low-Earth orbit (LEO) at a per-kilogram cost that is one to two orders of magnitude lower than current launch systems, using only a relatively small capital investment (comparable to a single large present-day launch). An attractive payload would be large quantities of high-performance chemical rocket propellant (e.g. LO<sub>2</sub>/LH<sub>2</sub>) that would greatly facilitate, if not enable, extensive exploration of the moon, Mars, and beyond. The concept is to use small, mass-produced, two-stage, LO<sub>2</sub>/LH<sub>2</sub>, pressure-fed rockets (e.g. without turbo-pumps, which increase performance but are costly). These small rockets can reach orbit with modest atmospheric drag losses because they are launched from very high altitude (e.g. 22 km). They reach this altitude by being winched up a tether to a balloon that is permanently stationed there. The drag losses on a rocket are strongly related to the ratio of the rocket launch mass to the mass of the atmospheric column that is displaced as the vehicle ascends from launch to orbit. By reducing the mass of this atmospheric column to a few percent of what it would be if launched from sea level, the mass of the rocket can be proportionately reduced while maintaining drag loss at an acceptably small level. The system concept is that one or more small rockets would be launched to rendezvous on every orbit of a propellant depot in LEO. There is only one orbital plane where a depot will pass over the launch site on every orbit - the equator. Fortunately, the U.S. has two small islands virtually on the equator in the mid-Pacific (Baker and Jarvis Islands). Launching one on every orbit, approximately 5,500 rockets would be launched every year, which is a manufacturing rate that allows significantly reduced manufacturing costs, especially when combined with multi- year production contracts, giving a projected propellant cost in LEO of $400/kg - or less. The configuration of the proposed propellant depot and the manner in which the propellant would be utilized has already been reported. The launch processing facility (a small, modified container ship) and cable-car that moves the rocket on the tether have also been reported. The work described in this progress report focuses on a simplified dynamic simulation of the ascent of the rocket, comparing spin-stabilization with 3-axis stabilization in terms of minimizing the amount of propellant drawn from the payload tank needed for head-end vernier thruster control of the stack during ascent. Implications for the vernier thruster configuration and control algorithm are discussed. This paper describes the derived design, including overall geometry, component configurations, refined balloon-tether architecture, and expected system performance.
    Aerospace conference, 2009 IEEE; 04/2009
  • B.H. Wilcox
    [Show abstract] [Hide abstract]
    ABSTRACT: As part of the NASA Exploration Technology Development Program, the Jet Propulsion Laboratory is developing a vehicle called ATHLETE: the all-terrain hex-limbed extra-terrestrial explorer. The vehicle concept is based on six wheels at the ends of six multi-degree-of-freedom limbs. Because each limb has enough degrees of freedom for use as a general-purpose leg, the wheels can be locked and used as feet to walk out of excessively soft or other extreme terrain. Since the vehicle has this alternative mode of traversing through (or at least out of) extreme terrain, the wheels and wheel actuators can be sized only for nominal terrain. There are substantial mass savings in the wheels and wheel actuators associated with designing for nominal instead of extreme terrain. These mass savings are comparable-to or larger-than the extra mass associated with the articulated limbs. As a result, the entire mobility system, including wheels and limbs, can be about 25% lighter than a conventional mobility chassis for planetary exploration. A side benefit of this approach is that each limb has sufficient degrees-of-freedom for use as a general-purpose manipulator (hence the name ldquolimbrdquo instead of ldquolegrdquo). Our prototype ATHLETE vehicles have quick-disconnect tool adapters on the limbs that allow tools to be drawn out of a ldquotool beltrdquo and maneuvered by the limb. A rotating power-take-off from the wheel actuates the tools, so that they can take advantage of the 1+ horsepower motor in each wheel to enable drilling, gripping or other power-tool functions.
    Aerospace conference, 2009 IEEE; 04/2009
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: As previously reported [1], it may be possible to launch payloads into low-Earth orbit (LEO) at a per- kilogram cost that is one to two orders of magnitude lower than current launch systems, using only a relatively small capital investment (comparable to a single large present-day launch).11 An attractive payload would be large quantities of high-performance rocket propellant as required for the exploration of the moon, Mars, and beyond. The concept is to use small mass-produced rockets that can reach orbit with modest atmospheric drag losses because they are launched from high altitude (e.g. 22 km). These small rockets launch from this altitude by being winched up a tether to a balloon. The drag losses on a rocket are strongly related to the ratio of the rocket launch mass to the mass of the atmospheric column displaced as the vehicle ascends from the launch site to orbit. By reducing the mass of this atmospheric column to a few percent of what it would be launching from sea level, the mass of the rocket can be proportionately reduced while maintaining the drag loss at an acceptably small level.
    Aerospace Conference, 2008 IEEE; 04/2008
  • B.H. Wilcox
    [Show abstract] [Hide abstract]
    ABSTRACT: As part of the NASA Exploration Technology Development Program, the Jet Propulsion Laboratory is developing a vehicle called ATHLETE: the all-terrain hex-limbed extra-terrestrial explorer. Each vehicle is based on six wheels at the ends of six multi-degree-of-freedom limbs. Because each limb has enough degrees of freedom for use as a general-purpose leg, the wheels can be locked and used as feet to walk out of excessively soft or other extreme terrain. Since the vehicle has this alternative mode of traversing through or at least extracting itself out of extreme terrain, the wheels and wheel actuators can be sized for nominal terrain. There are substantial mass savings in the wheel and wheel actuators associated with designing for nominal instead of extreme terrain. These mass savings are comparable-to or larger-than the mass increase of the articulated limbs. As a result, the entire mobility system, including wheels and limbs, can be lighter than a conventional mobility chassis. In addition, each limb has sufficient degrees-of-freedom to use as a general-purpose manipulator. Our prototype ATHLETE vehicles have quick-disconnect tool adapters on the limbs that allow tools to be drawn out of a "tool belt" and positioned by the limb. A power-take-off from the wheel actuates the tools, so that they can take advantage of the 1+ horsepower motor in each wheel to enable drilling, gripping or other power-tool functions. One of the most attractive uses for ATHLETE limbs is as part of a "mobile lander". Lunar landers are traditionally conceived-of as static - remaining stationary after landing on pads that deploy to a large radius to reduce the likelihood of overturning and that incorporate energy absorption (e.g. crushable materials) to cushion whatever residual impact remains after the rocket propulsion system is shut down. Landers implicitly integrate all the subsystems required for a complete spacecraft-power, communications, computation, inertial sensing, etc. All these s- ubsystems would need to be re-implemented on any rover that deploys from a lander. Instead, these subsystems can be used "as-is" (perhaps with additional qualification testing) if only the lander were equipped with post-landing mobility. This obvious advantage of mobile landers has been recognized for decades (see Section 3), but use of ATHLETE limbs as landing outriggers together with crushable materials under the primary structure of the lander combines the benefits of the reduced mobility mass and tool-use of the ATHLETEconcept with the intrinsic efficiency of the mobile lander concept.
    Aerospace Conference, 2008 IEEE; 04/2008
  • Source
    B. Wilcox
    [Show abstract] [Hide abstract]
    ABSTRACT: Propellant will be more than 85% of the mass that needs to be lofted into low Earth orbit (LEO) in the planned program of exploration of the Moon, Mars, and beyond. This paper describes a possible means for launching thousands of tons of propellant per year into LEO at a cost 15 to 30 times less than the current launch cost per kilogram. The basic idea is to mass-produce very simple, small and relatively low-performance rockets at a cost per kilogram comparable to automobiles, instead of the ~>25times greater cost that is customary for current launch vehicles that are produced in small quantities and which are manufactured with performance near the limits of what is possible. These small, simple rockets can reach orbit because they are launched above >95% of the atmosphere, where the drag losses even on a small rocket are acceptable, and because they can be launched nearly horizontally with very simple guidance based largely on spin-stabilization. Launching above most of the atmosphere is accomplished by winching the rocket up a tether to a balloon. A fuel depot in equatorial orbit passes over the launch site on every orbit (approximately every 90 minutes). One or more rockets can be launched each time the fuel depot passes overhead, so the launch rate can be any multiple of ~6000 small rockets per year, a number that is sufficient to reap the benefits of mass production
    Aerospace Conference, 2006 IEEE; 01/2006

Publication Stats

32 Citations

Institutions

  • 2008–2010
    • California Institute of Technology
      • Jet Propulsion Laboratory
      Pasadena, CA, United States