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69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 1 of 9
IAC-18.D2.8
Payload Utilization in NASA’s Space Launch System
Stephen D. Creecha*, Dr. Kimberly F. Robinsonb
a Spacecraft/Payload Integration & Evolution Office, NASA’s Space Launch System, Marshall Space Flight Center,
Huntsville, AL 35812 U. S. A., steve.creech@nasa.gov
b Spacecraft/Payload Integration & Evolution Office, NASA’s Space Launch System, Marshall Space Flight Center,
Huntsville, AL 35812 U. S. A., kimberly.f.robinson@nasa.gov
* Corresponding Author
Abstract
With Space Policy Directive 1, the United States administration has directed the National Aeronautics and Space
Administration’s (NASA’s) Human Exploration & Operations Mission Directorate (HEOMD) to return to the Moon
with missions and infrastructure designed to support a sustained presence in cislunar space, with robotic and human
lunar surface operations. NASA’s new deep space exploration system — the super heavy-lift Space Launch System
(SLS), the Orion crew spacecraft and revamped launch facilities at Kennedy Space Center (KSC) — will enable
NASA and its commercial and international partners to meet this goal for human exploration of deep space. SLS is
the most capable launch vehicle for these efforts, as well as for sending robotic missions deep into the solar system,
or even to interstellar space. The vehicle will be available in crew and cargo configurations in progressively more
powerful block variants. The initial Block 1 lift capability of at least 26 metric tons (t) to trans-lunar injection (TLI)
will be followed by a more powerful Block 1B with the power to loft more than 37 t to TLI. The ultimate Block 2
variant will lift more than 45 t to TLI. For payload accommodation, the Block 1 vehicle can utilize a 5 meter (m)
fairing in its cargo configuration with the crew version also able to provide berths for 6U and 12U CubeSats as
secondary payloads. The Block 1B crew vehicle will provide as much volume as the space shuttle payload bay in a
Universal Stage Adapter (USA) for co-manifested payloads (CPLs). Block 1B cargo vehicles will offer 8.4 m-
diameter fairings in 19.1 m and possibly longer lengths, with enough volume to accommodate lunar-orbiting habitat
modules and other elements of NASA’s Gateway science outpost. For Mars-class payloads, larger fairings for the
Block 2 cargo launcher are under consideration. For missions beyond the Earth-Moon system, SLS offers greater
characteristic energy (C3) than any other launch vehicle, enabling shorter transit times or heavier payloads with more
robust science packages for missions to the outer solar system. Indeed, the unmatched combination of thrust, payload
volume and departure energy that SLS provides opens new opportunities for human and robotic exploration of deep
space. This paper will provide an overview of the various vehicle block configurations, their capabilities and payload
accommodations for sending primary, co-manifested and secondary payloads to deep space.
Keywords: NASA, Space Launch System, launch vehicles, payloads, lunar orbit, CubeSats
Acronyms/Abbreviations
National Aeronautics and Space Administration (NASA), Space Launch System (SLS), Exploration Mission-1
(EM-1), Exploration Missoin-2 (EM-2), low-Earth orbit (LEO), trans-lunar injection (TLI), metric tons (t), Human
Exploration & Operations Mission Directorate (HEOMD), Exploration Ground Systems (EGS), evolved expendable
launch vehicles (EELVs), EELV Secondary Payload Adapter (ESPA), distant retrograde orbit (DRO), characteristic
energy (C3), Vertical Assembly Center (VAC), Interim Cryogenic Propulsion Stage (ICPS), Marshall Space Flight
Center (MSFC), Stennis Space Center (SSC), Kennedy Space Center (KSC), Orion Stage Adapter (OSA), Launch
Vehicle Stage Adapter (LVSA), commercial off-the-shelf (COTS), United Launch Alliance (ULA), Delta Cryogenic
Second Stage (DCSS), liquid hydrogen (LH2), liquid oxygen (LOX), Vehicle Assembly Building (VAB), Launch
Abort System (LAS), Launch Complex 39B (LC39B), astronomical units (AU), payload fairing (PLF), co-
manifested payload (CPL), payload attach fitting (PAF), payload separation system (PSS), payload interface adapter
(PIA).
1. Introduction
The first mission of the National Aeronautics and
Space Administration’s (NASA’s) new super heavy-lift
launch vehicle, the Space Launch System (SLS), and the
Orion spacecraft, launching from upgraded and
refurbished facilities at Kennedy Space Center (KSC),
will send the Orion crew vehicle into lunar distant
retrograde orbit (DRO) on a flight test known as
Exploration Mission-1 (EM-1). This mission, scheduled
to last about 25 days, will enable NASA to verify and
https://ntrs.nasa.gov/search.jsp?R=20180007878 2020-03-03T20:03:34+00:00Z
69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 2 of 9
validate new systems before sending astronauts to deep
space on Exploration Mission-2 (EM-2). With these
exploration missions, NASA will mark the return of its
human exploration programs to cislunar space for the
first time since the Apollo 17 mission in 1972.
NASA plans to use the SLS Block 1 crew vehicle
for the first two exploration missions. The SLS
Program, managed at Marshall Space Flight Center
(MSFC) in Huntsville, Alabama, U.S.A., and its prime
contractors, have made substantial progress toward first
launch, with several major components of the vehicle
complete and delivered to the Exploration Ground
Systems (EGS) Program at KSC, which has
responsibility for stacking and launching the system.
With a planned path forward of progressively more
powerful vehicles available in both crew and cargo
configurations, SLS will provide the lift capability,
payload capacity and departure energy to make the
world’s most demanding missions a success. In fact,
SLS offers power, volume and characteristic energy
(C3) that haven’t been seen since the Saturn vehicles,
opening options for transformative human exploration
and science missions.
2. Cornerstone of NASA’s Deep Space Exploration
System
SLS is not one launcher. Rather, it’s a system of
launch vehicles suitable for a variety of super heavy-lift
missions to a variety of destinations beyond low-Earth
orbit (LEO). The major variants, Block 1, Block 1B and
Block 2, provide incrementally improved lift
capabilities; each block variant will be available in crew
and cargo configurations. Cargo configurations will
utilize payload fairings (PLFs) in a variety of sizes,
from industry-standard 5-meter (m) diameter to 8.4-m
diameter, with larger diameter fairings under evaluation.
Figure 1. NASA’s Block 1 Space Launch System (SLS) and Orion spacecraft
69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 3 of 9
For all vehicles in the series, primary propulsion will
be supplied by two boosters and four liquid
hydrogen/liquid oxygen (LH2/LOX)-fueled RS-25
engines. For the first two variants, Block 1 and Block
1B, the boosters and engines are derived from the Space
Shuttle Program but upgraded to meet more stringent
SLS performance requirements and more extreme
operating environments. An all-new core stage will
house the propellant tanks, the four RS-25 engines, the
flight computers and provide the attach points for the
boosters. Towering 64.6 m, the SLS core stage is the
largest rocket stage ever constructed in terms of volume
and length and required the world’s largest spacecraft
welding tool, the Vertical Assembly Center (VAC), for
joining the sections. The VAC was installed at NASA’s
historic Michoud Assembly Facility near New Orleans,
Louisiana, U.S.A., and the friction-stir welding tool has
produced a series of test and flight hardware for the first
two missions. The upper stage and payload sections of
the vehicles, in addition to required adapters, will vary
according to block configuration and will be discussed
below. To meet its ultimate lift capability of at least 45 t
to TLI, Block 2 will feature upgraded boosters for
maximum performance.
3. Initial Capability: SLS Block 1
The first vehicle to fly will be the Block 1 crew
variant, which will send an uncrewed Orion to a lunar
Figure 2. The evolutionary block upgrade path for SLS
Figure 3. SLS propellant tanks manufactured at
Michoud Assembly Facility
69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 4 of 9
Distant Retrograde Orbit (DRO) for the first mission,
EM-1. The EM-1 vehicle is nearing completion. The
four RS-25 engines have been hot-fire tested at Stennis
Space Center (SSC) and upgraded with state-of-the-art
computerized controllers. The EM-1 engines stand
ready for integration with the core stage. The five-
segment solid rocket motors, of a similar design to
shuttle-era solid motors but 20 percent more powerful
with an additional propellant segment and different
grain geometry, as well as new case insulation and
avionics, are also complete for the first flight.
Technicians are completing refurbishment on the
forward and aft booster assemblies; avionics testing is
underway. One section of the core stage, the forward
skirt, is complete and the other parts of the stage are
undergoing final installation of internal subsystems.
Then, the major sections of the stage will be joined at
Michoud to create the EM-1 vehicle’s core stage.
Forward work on the EM-1 vehicle, in addition to
joining the sections of the core stage, includes
integrating the four RS-25 engines into the stage and
shipping the stage to SSC for a “green run” hot-fire test.
Above the core stage, a single-engine LH2/LOX-
based Interim Cryogenic Propulsion Stage (ICPS) will
provide the burn to send Orion to TLI during EM-1.
Essentially an off-the-shelf United Launch Alliance
(ULA) Delta Cryogenic Second Stage (DCSS), the
ICPS required a few modifications for EM-1:
lengthening the LH2 tank, adding hydrazine bottles for
attitude control and a few minor avionics changes. The
Program delivered the ICPS to EGS well ahead of
schedule and it stands ready for integration with the rest
of the vehicle.
Two adapters connect the ICPS to the core stage
below it and Orion’s spacecraft adapter above it.
Technicians are putting the finishing touches on the
Launch Vehicle Stage Adapter (LVSA) at MSFC; the
Orion Stage Adapter (OSA) is complete and has been
delivered to KSC. For the EM-1 test flight, the OSA
provides payload berths for 13 6U smallsats and one
avionics unit. These secondary payloads will be released
into deep space following separation of Orion from the
ICPS along its disposal trajectory. The SLS Program
provided a secondary payload deployment system
consisting of mounting brackets for commercial off-the-
shelf (COTS) dispensers, cable harnesses and the
avionics unit. For future missions, the system is capable
of supporting up to 17 CubeSats in a combination of 6U
and 12U configurations.
The Block 1 cargo configuration will use an ICPS
upper stage and an industry-standard 5 m-diameter
fairing. This configuration is under consideration for a
Figure 2. New work platforms have been installed in Kennedy Space Center’s Vehicle Assembly Building for
stacking the SLS vehicles
69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 5 of 9
launch sending the “Europa Clipper” probe on a direct
trajectory to the icy Jovian moon. At the time of writing,
procurement was underway for the cargo shroud,
payload adapter, separation system and other associated
hardware. Use of industry-standard payload interfaces
and accommodations in the Block 1 cargo vehicle will
streamline development processes for Europa Clipper
mission planners and engineers.
All Block 1 vehicles will be stacked in KSC’s
historic Vehicle Assembly Building (VAB), where the
EGS Program has removed the platforms used to stack
space shuttles and replaced them with 10 new platforms.
The new work platforms soar nearly to the top of the
160-m tall High Bay 3, where SLS and Orion, with its
Launch Abort System (LAS), will be integrated. The
new system will launch from Launch Complex 39B
(LC39B) at KSC on Mobile Launcher (ML) 1, which
has also been refurbished for SLS and Orion. In fact, the
EGS Program recently completed installation of all
umbilicals on the ML for EM-1.
4. Interim Capability: SLS Block 1B
SLS Block 1B will use the same core stage design,
with only minor modifications, as the Block 1 vehicles.
To improve performance, the solid rocket boosters and
four RS-25 engines will incorporate new technologies,
with the four RS-25 engines expected to perform at 111
percent of shuttle-era maximum power levels. The
primary means of increasing mass to TLI will be
through a new upper stage, termed the Exploration
Upper Stage (EUS). This four-engine LH2/LOX stage
will team with the newly manufactured RS-25s and
upgraded boosters to allow SLS to deliver between 34
to 37 t of payload to cislunar space, depending on crew
or cargo configuration. The EUS will provide both
ascent/circularization and in-space transportation for
payloads. The Block 1B capability is scheduled to come
into service beginning with the fourth SLS flight and
will launch from a second ML at KSC’s LC39B.
The Block 1B crew vehicle can accommodate Orion
and a co-manifested payload (CPL) in the Universal
Stage Adapter (USA), which provides as much volume
for payloads as industry-standard 5 m fairings. The
Program anticipates lift capability of up to 10 t for
CPLs, which will typically separate from the EUS
between five and eight hours post-launch, after reaching
a safe distance from the crew vehicle.
The USA can offer various sizes of access doors to
facilitate a variety of payloads and an interior surface
compatible with acoustic treatments to meet
environmental requirements. Once on orbit, after Orion
separates from the USA, the USA separates in a
“canister” fashion (in contrast to typical fairing “sector”
separations). The canister separation scheme results in
Figure 3. Notional payload accommodations for primary, co-manifested and secondary payloads in SLS Block
1B and Block 2 crew and cargo configurations
69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 6 of 9
Science PPL 7.2m Module PPL
USA PLF
47’
(14 m)
8.4m PLF
63’
(19 m)
PIA/PSS
Payload
Adapter PAF PAF/PSS
SLS Payload Adapter Combinations
4.5m Module CPL
Payload
Adapter
8.4m USA
the upper 85 percent of the USA structure, with the
Orion spacecraft adapter still attached, being jettisoned
as a single, circumferential ring. The non-separable 15
percent of the USA structure remains with the EUS; its
height is less than the payload adapter separation plane
in order to facilitate CPL extraction by Orion, or
separation as an independent system.
Similar to evolved expendable launch vehicles
(EELVs), the mechanical interface between the SLS
Block 1B launch vehicle and a primary payload or CPL
is a payload adapter
consisting of up to three
components as shown in
Figure 6. Choice of a
particular payload adapter is
mission-dependent.
A payload attach fitting
(PAF) is a structural/service
interface to the 8.4 m-
diameter SLS EUS forward
adapter. The PAF can be
configured with a payload
interface adapter (PIA)
and/or a payload separation
system (PSS) to
accommodate different
spacecraft or payload
interfaces. The PIA is an
optional interface between
the PAF and the spacecraft
or payload that maximizes
available volume. The PIA
accommodates a PSS,
which is a structural
separation interface for a
spacecraft or payload
mounted on the PAF or
PIA. Depending on the
interface diameter required,
it can support a variety of
COTS separation systems
(e.g., D1666 or 1666VS) or a new-development
separation system.
For secondary payloads, rideshare opportunities for
up to 21 smallsats up to 27U in size may be offered on
the payload adapter in the USA. Depending on the
requirements of PPLs or CPLs, it might also be possible
to deploy larger “ring payloads,” similar to those
currently flown on an EELV Secondary Payload
Adapter (ESPA).
The Block 1B cargo configuration can accommodate
payloads using an 8.4 m diameter fairing in varying
lengths. As with CPLs on the Block 1B crew
configuration, the EUS forward adapter provides an
interface for various payload fairings and payload
adapters.
5. Ultimate Capability: SLS Block 2
The eventual Block 2 crew variant will use an
advanced booster to maximize performance, enabling
the vehicle to place at least 45 t in lunar orbit. This
configuration will also take advantage of future
developments in technology, while providing unique
enabling capabilities for human Mars missions. Fairings
larger than 8.4 m diameter in varying lengths are being
evaluated. The Block 2 vehicle has the potential to carry
Figure 6. SLS Block 1B payload adapter components
Figure 4. SLS accommodates a range of fairings
69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 7 of 9
10 m fairings with a volume of up to 1,800 m3, several
times greater than any currently available fairing,
making new missions possible and streamlining design
of deep space spacecraft.
6. System Benefits and Outreach
SLS offers substantial benefits to spacecraft
designers and mission planners in terms of greater mass,
volume and departure energy than EELVs can provide.
These primary benefits make possible a variety of
secondary benefits too. For example, greater payload
volume and mass can decrease the need for
miniaturization and origami-like deployments, thus
simplifying the spacecraft design cycle, as well as
complexity and risk. Reducing
transit time by enabling a direct
trajectory without gravitational
assists reduces mission risk and
operational cost, and can eliminate
the need to design for inner solar
system conditions.
Program managers envision an
eventual flight processing throughput
capacity of two to three SLS flights
per year, making flight opportunities
available to NASA mission
directorates, international partners,
private industry, academia and other
government agencies. SLS can
accommodate primary payloads,
CPLs and secondary payloads and is
actively engaged with the science
community to understand demand
and provide information on the
unique capabilities of the evolvable
system. The SLS Program has an SLS
Mission Planner’s Guide available in
a downloadable PDF format, to provide basic technical
details on the SLS system, including configurations:
https://ntrs.nasa.gov/search.jsp?R=20170005323.
7. Mission Opportunities
While the primary purpose of SLS is to enable
human exploration of the solar system with the Moon as
a foundational proving ground, a myriad of mission
types will benefit from the mass, volume and departure
energy that SLS provides, including planetary science,
astrophysics, heliophysics, planetary defense and
commercial endeavors.
7.1 Lunar Missions
NASA’s Human Exploration & Operations Mission
Directorate (HEOMD) has outlined plans for a new
lunar orbiting science outpost, the Gateway, to be
constructed in the 2020s. The Gateway will serve as a
proving ground for technology and science missions to
both better understand the Earth-Moon system and
inform future missions to Mars and deeper into the solar
system. The superior lift and payload volume abilities of
SLS Block 1B will enable the Agency to send Orion and
a CPL, such as a habitat module or a reusable lunar
lander for astronauts, to the Gateway in a single launch.
Opportunities for international collaboration on
Gateway components that will go to the outpost as
CPLs will enhance international cooperation while
commercial vehicles have a role to play providing
logistics flights and delivery of other elements. For
deploying more massive Gateway infrastructure, Block
1B cargo flights featuring the 8.4 m fairing in varying
lengths will be available in the 2020s. The super heavy-
lift capability of SLS may yield a significant mass
margin that can be used to carry additional consumables
or secondary payloads in 6U, 12U or larger sizes.
Figure 8. SLS vehicles can deliver a range of useful payload mass, shown
here in the form of a C3 curve
Figure 9. SLS can deliver the Orion crew vehicle
and co-manifested payloads (CPLs) to NASA’s lunar
Gateway
69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 8 of 9
7.2 Mars Missions
With the construction of the lunar Gateway and
proving out deep space technologies as an intermediate
step, Mars remains an Agency – and international –
horizon goal. In addition to sending astronauts to the
Moon to expand knowledge of working in deep space
environments, SLS may be used to launch future
missions to Mars using a fully evolved Block 2 SLS
vehicle.
7.3 Missions to the Outer Planets
Science Mission-1 (SM-1), the Europa Clipper
mission notionally launching on the Block 1 cargo
vehicle, provides a case study for utilization of the
superior SLS departure energy to shorten cruise time,
enabling faster data return and simpler mission design.
SLS can directly inject this flagship science mission into
Jovian space, eliminating the seven-to-eight-year
Venus-Earth-Earth gravitational assist trajectory a Delta
IV Heavy would require to send the spacecraft to
Jupiter’s icy ocean moon. With the Block 1 SLS
vehicle, transit to Europa will be less than three years,
providing earlier science return and reduced operational
costs. In addition, a shorter outbound cruise phase
means the spacecraft needs less radiation shielding and
saves mass, which can translate to a more robust science
payload. If a follow-on Europa lander mission comes to
fruition, that mission could use the performance of SLS,
not for decreased transit time, but for increased mass,
using a gravitational-assist trajectory to deliver a large
payload with a launch mass of 16 t. In addition, the
earlier science return of the Clipper mission will inform
the lander study.
Looking farther into the solar system, scientists
could utilize the unique capabilities of SLS to send a
small probe to the giant ice worlds of Uranus and
Neptune to investigate the atmospheric and magnetic
properties and conduct flybys of larger satellites. SLS
can send spacecraft on direct trajectories to these
systems also, opening new horizons for exploration with
faster data return for investigators.
7.4 Astrophysics Missions
In the field of astrophysics, the unmatched payload
volume in SLS
fairings,
whether 8.4 m
or potentially
larger fairing,
facilitates
launch of large-
aperture
telescopes that
could put a
view of cosmic
dawn – or life
on exoplanets –
within our
reach. The
unmatched
payload volume
of SLS could be
used to deploy
telescopes
potentially as
large as 16 m to
make ultra-
high-contrast
spectroscopic
observations of
exoplanets or
image the first
galaxies. Such a
capability would
address a need
identified in the 2013 NASA astrophysics roadmap,
“Enduring Quests, Daring Visions.” A space telescope
larger than the James Webb Space Telescope could be
engineered to utilize the largest fairing under study – a
10 m-diameter, 27.4-m long fairing. Such a telescope
could be stationed at a Sun-Earth Libration Point to
Figure 10. SLS can launch the “Europa Clipper” on a direct trajectory to Jovian space,
without gravity assists
69th International Astronautical Congress (IAC), Bremen, Germany, 1-5 October 2018.
IAC-18.D2.8 Page 9 of 9
allow scientists to explore the universe, characterize
supermassive black holes, investigate the history of
hundreds of galaxies and uncover the secrets of dark
matter.
7.5 Interstellar Medium Missions
SLS could be used to send a small probe to
interstellar space, in concert with a skillfully designed
mission, to explore the interstellar medium. Maximizing
the staging efficiency to reduce flight times could
enable a project goal of achieving 1,000 AU in 50 years.
Mission concepts include investigation of the interstellar
medium and its influence on the solar system, and the
characterization of interstellar gas, low-energy cosmic
rays, dust and magnetic fields.
Using the Sun as a gravitational focus in order to
study features on distant exoplanets is another mission
concept that SLS could enable. Einstein’s Theory of
General relativity predicts that light bends around a
massive object – such as the Sun. However, the effect is
tiny and only observable at significant distance from
objects of enormous mass. Consequently, the focal point
of a solar lens must be at least 550 AU distant, beyond
Pluto’s orbit and past the Kuiper Belt, which extends a
mere 50 AU. SLS could be used to deploy a telescope at
the focal line of the gravitational lens in order to study a
distant exoplanet in unprecedented detail.
7. Conclusion
With the first Block 1 crew vehicle nearing
completion and the EM-1 test flight of NASA’s new
deep space exploration system squarely within view, a
new era of deep space exploration is dawning. With
SLS, Orion and EGS, NASA will once again have the
capability to send astronauts to the Moon and safely
return them to Earth. This lunar exploration campaign
of the 2020s, however, will be a sustained and
cooperative effort among NASA and its partners to live,
explore, investigate, demonstrate and innovate off-
planet operations using the lunar Gateway.
Technologies developed for lunar exploration will be
tested with an eye toward Mars and the rest of the solar
system. With SLS, NASA
has a vehicle with a
clear evolutionary
path to meet the
nation’s most
demanding missions,
whether that’s
sending astronauts in
the capable Orion
crew vehicle to the
Gateway along with
a CPL of significant
size and volume, or
whether it’s
launching a flagship
science mission as a
cargo-only flight
deep into the solar
system. The mass,
volume and
departure energy
SLS provides
presents
spacecraft designers and mission planners with new and
unique opportunities for astrophysics, planetary science,
in situ exploration, sample return and other ambitious
missions. Larger science packages and reduced cruise
times put many once out-of-reach missions within
reach, in our lifetimes.
The answers to the most profound questions about
the cosmos may be within our reach.
Figure 11. SLS provides unique benefits for a number science missions