The nation's efforts to expand human presence and activity beyond Earth orbit into the solar system was given renewed emphasis in January of 1988 when the Presidential Directive on National Space Policy was signed into effect. The expansion of human presence into the solar system has particular significance, in that it defines long-range goals for NASA's future missions. To embark and achieve such ambitious ventures is a significant undertaking, particularly compared to past space activities. Missions to Mars, the Moon, and Phobos, as well as an observatory based on the dark side of the Moon are discussed

Cataldo, Robert L.

English

NASA Technical Reports Server

N90-20457
HUMAN EXPLORATION MISSION STUDIES
Robert L. Cataldo
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135
The nation's efforts "to expand human presence and activity beyond Earth
orbit into the solar system" was given renewed emphasis in January of 1988
when the PresldentiaI Directive on National Space Policy was signed Into
effect. The expansion of human presence into the solar system has particular
significance, In that it defines long-range goals for NASA's future missions.
To embark and achieve such ambitious ventures Is a significant undertaking,
particularly compared to past space activities.
INTRODUCTION
Two major efforts recently released, the National Commission on Space
Report, "Pioneering the Space Frontier," 1986, and astronaut Dr. Sally Ride's
task force report, "Leadership and America's Future in Space," 1987, have
helped set goals and give focus to NASA's future direction. Dr. Ride's task
force formulated a plan to achieve the Commission's proposed agenda for the
civilian space program. The task force recommended four initiatives: (1) Mls-
slon Planet Earth, (2) Exploration of the Solar System, (3) Outpost on the
Moon, and (4) Humans to Mars. The first two initiatives, to a great degree,
are being pursued by NASA's Office of Space Science and AppIicatlons. However,
the last two Initiatives prompted the task force to recommend that a speclal
NASA office be established to coordinate and lead human exploratlon studies.
Therefore, the Office of Exploration was established to provide a focal point
for these actlvltles. These include establishing a mature understanding of
mission options and opportunities and deflnlng those near-term activities that
can provide the greatest Impact on future missions.
The Office of Exploration has establlshed a process whereby all NASA
field centers and other NASA Headquarters offices participate In the formula-
tion and analysis of a wlde range of mission strategles. These strategies
were manifested Into specific scenarios or candidate case studies. The case
studies provided a systematic approach into analyzlng each mission element.
First, each case study must address several major themes and rationale Includ-
ing: national pride and international prestige, advancement of scientiflc
knowledge, a catalyst for technology, economic benefits, space enterprise,
International cooperation, and education and exce]Ience. Second, the set of
candidate case studies are formulated to encompass the technology requlrement
limits in the life sciences, launch capabilities, space transfer, automation
and robotics, in-space operations, power, and propulsion.
The first set of reference case studies identify three major strategies:
(1) human expeditions, (2) science outposts, and (3) evolutionary expansion.
During the past year, four case studies were examined to explore these strate-
gies. The expedltionary mlsslons include the Human Expedition to Phobos and
Human Expedltlon to Mars case studles. The Lunar Observatory and Lunar
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https://ntrs.nasa.gov/search.jsp?R=19900011141 2020-03-19T22:43:53+00:00Z
Outpost to Early Mars Evolution case studies examined the later two strate-
gies. Thls set of case studles established the Frameworkto perform detailed
mission analysls and system engineering to define a host of concepts and
requirements for various space systems and advanced technologles. This paper
describes the details of each mission and, speciflcally, the results
affecting the advanced technologles required to accompllsh each mission
scenario.
MISSIONSTUDIES
The office of Exploratlon has establlshed a process Wherebyreference
case studies are examinedyearly. This a11owsfora_easonable subset of
Op_|6ns to be stud|ed in=s6medetail in order to establish flrst order effects
and _rends in var_s system elements. Once the StUdy h_een characterlzed
in sufficient depth, different system elements can be replaced with new
options so that the overall system performance sensltlvlties can be analyzed.
The broad scope in case studies is engineered to provide_a wide range of mls-
sion options and to avoid making priorities between exploring the Moonor Mars.
The followlng candidate case studies are the first set of options studied
in 1988. These options are not the final set, in fact, during the coming
years these cases may be refined and new cases added, to form a comprehensive
set of options so that qualified engineering decisions can be made in the
final selection process for those studies that will be carried forward into a
program phase A/B
HUMAN EXPEDITION TO PHOBOS
A manned expedltlon to Phobos, the inner Martian _on_would establlsh an
early U.S. exploration leadershlp. Actlvltles such as exploration, resource
survey and science station set up would be conducted. Also, a fleet of small
teleoperated "low-tech" rovers could provide enhanced exploratlon of the Mar-
tian surface. The expedltion to Phobos satisfies two objectives, that of
human exploration and previously studied robotic missions with sample return
options.
Past spectral analysis of both Phobos and Delmos suggest that materials
are present that could Justlfy ]everaging rocket propellants for future return
trips from MarsJ Prop_lant production plants could allow vehicles to carry
fuel only for the trans Earth-Mars leg, and refuel at Phobos or Deimos for the
trans Mars-Earth leg. Earth to orbit (ETO) mass could be significantly
reduced, partlcularly with an evolutlonary Mars mlsslon. The Phobos misslon
a]so relieves the pressure on the launch transportatlon systems, because of
reduced propellant mass required by not ]andlng on Mars itself.
......... Mission_cen:ario
The Phobos expedition employs a "spiit/sprlnt" transportation scheme
where a cargo vehicle carrying science equipment, crew return propellant and
Mars rovers would be launched on a minimum energy trajectory. About 10 months
later, the vehicle carrying a crew of four on a high-energy sprint class
lO
=
Im
trajectory Is launched. Nine months later the crew vehicle mates with the
cargo vehicle in Mars orbit. Two crew members then board an excursion vehicle
and conduct the mission objectives on Phobos, The two remaining crew members
teleoperate rovers on the Martian surface and transfer propellant from the car-
go vehicle. After about 30 days In the Mars system the four crew members re-
turn to Earth having been away from Earth a total of 14 months.
HUMAN EXPEDITION TO MARS
Since the invention of the telescope, Mars, with Its observed global dust
storms and "canal1", has been a favorlte destination for planetary exploratlon
and colonization. Mars has been called Earth's sister planet because of their
slmilarlties, although it is not a very hospitable planet for humans. Sclen-
tlsts have speculated that Mars had more of Earth's characteristics, denser
atmosphere water for example, which could have supported llfeforms early In
its evolution. Thus, there Is a large international segment of the population
that suggests we return to explore Mars with manned missions.
Mission Scenario
The Mars Expedition calls for three separate segments launched on suc-
cessive opportunities. The first segment Includes a cargo vehicle preceding
the eight member crew on a splltlsprlnt approach as In the Phobos mission.
However, the cargo vehicle that transports rovers, surface habitats, and explo-
ration and science equipment is placed in Mars orbit. After spacecraft ren-
dezvous, four crew members descend to the surface in the landing craft for a
20 day stay. The exploratlon party will perform science experlments and pos-
sibly explore the surface for water, minerals, volatiles, and blologlcal traces
of present and past llfeforms. The crew will live in the pre-landed habltats
and utilize the rover for extended exploration. The remaining crew members In
orbit will transfer propellant from the cargo vehicle, perform orbltal science
and support surface operations. The surface crew will unite with the orbit
craft and return to Earth. The total length of the mission would span about
14 months. On ensuing trips exploration of Phobos and Delmos would also be
included In the scenarlo along with different landing sites on Mars.
LUNAR OBSERVATORY
The Lunar Observatory, comprised of optical telescope arrays, stellar mon-
itoring telescopes, and radio telescopes would encompass both the radio and
optical spectrum. An observatory, constructed on the far or backside of the
moon, could provide scientists with information orders of magnitude greater
than could be achieved From one in earth or in low-Earth-orbit. Significant
benefits of lunar locatlons are: clrcumventlng Earth's atmospheric Impedl-
ments, shielding of electromagnetic waves and providing a stable foundation
for large instruments and arrays.
Mission Scenario
An estimated four flights to the Moon's far slde would be required to
emplace the observatory. Two launches a year, one cargo and one crew, make up
II
the mission set. One combined crew/cargo flight per year would follow. The
crew of four would remain on the Moon's surface ooly during the Lunar day
using their lander vehicle as a habitat, similar to the Apollo missions. A
permanent base Is not required because of the short stay periods for maintain-
Ing the observatory about every 3 years and other exploration missions would
land at different sites.
Unpressurlzed rovers would be used as crew transports during the observa-
tory set up and maintenance, as well as automated machinery used for material
handling and scientific equipment transport.
LUNAR OUTPOST TO EARLY MARS EVOLUTION _
An evolutionary approach to space exploration is by building on the expe-
rlence of living and working on the Moon. The Moon is very attractive to
accomplish this since the transfer time back to Earth is only several days in
case an emergency situation would occur. A sustained human pressence on the
lunar surface would provide valuable data on working in reduced gravity, human
factors considerations with long duration planetary missions and learning how
to extract and utilize local resources.
A recommendation of the National Commission on Space (NCOS) was that a
"bridge between worlds" be built with the first step to develop the_Moonlthen
contlnue on to Mars. This case study defines the methodology necessary to
achieve that goal, by building a space exploration infrastructure that would
lead to nearly self-sufflclent space habltatlon. This, the most complex and
ambltlous scenario, stretches the limits of technologlcal advances in space
construction, utilization of Indigenous resources, life support, artiflcia]
gravity, chemical and electric propulsion, aerocapture, materlal and propellant
production and space power.
Mission Scenario
A series of both piloted and cargo flights would embark for the Moon.
Cargo would be sent on longer transfer trajectories using electric propulsion
and crews sent on fast chemically propelled transfer vehicles. It could take
several years to fully construct a surface facility, possibly with expediated
construction by vehicles operated from Earth. The pr!nciple goals of the base
is to produce materials and liquid oxygen used for Mars flights. The effort
to produce these products is leverage against the mass otherwise launched from
Earth.
Sometlme later, posslbly 6 to I0 years, the Mars flights would begin once
capabilities are sufflclent for the successful Mars trip. First, an electric
cargo vehicle would transport surface equipment, communications orbiters,
rovers, Mars-Phobos transfer vehlcles, scientiflc experiments and a Phobos
propellant plant. As the vehicle approaches Mars, it would deploy:
areosynchronous communication orbiters, robotic equipment to Deimos: and a
fuel processing plant to Phobos. The plant would produce fuel for future crew
return flights.
12
During the next Earth-Mars launch opportunity, the lunar electric cargo
vehicle will be reused to transfer the crew's transport vehicle to lunar orbit
for lunar derived oxygen fueling. The cargo/crew vehicle returns to Earth
orbit, and separates. The cargo vehicle stays in orbit for use as the next
ferry trip to the Moon, and the crew transport is boarded by the Mars crew.
After a systems checkout, they begin their 8 month journey. Several optlons
exist _s to Mars stay times; 60 days, l year, and 2 years. Continued flights
to Mars could occur every Earth-Mars opportunity which is about
26 months apart.
MISSION TECHNOLOGY REQUIREMENTS
As the case studies become more mature and focused, better deflned
requirements will emerge. However, the preliminary analysis of the 1988 case
studies have surfaced many technology areas needing further development.
These major areas include the following; surface exploration systems, fluid
management, propulsion, automation and robotics in-space operations, aerocap-
ture and power. Table I illustates key technologies as evaluated in relation
to the four case studies. Programs such as Pathflnder and the Civil Space
Technology Inltiatlve are planned to advance certain technologies that will
enable these missions. The requirements refined over the next few years will
provide these programs with mission technology goals. On the other hand, the
technologists must predict the degree to which the objective can be met
considering the techologlcal barriers and funding levels so that the proper
estimates can be integrated into the case studies. Significant scenario aug-
mentatlon reflecting the change in technology status may be necessary to
accomplish mission objectives.
POWER SYSTEM REQUIREMENTS
By design, the case studies span a range of complexity with the more
basic being the Expedition to Phobos and the more complex the Lunar Outpost to
Early Mars. The Lewis Research Center has been chartered by OEXP to perform
the power system analyses. These tasks Include doing broad trades as well as
in depth investigatlons. Major study areas include power systems for explora-
tion elements such as; electric cargo vehicles, planetary orbit transportation/
staging nodes, mobile equipment resource processing plants, surface science
outposts and habitated bases.
The power levels presented in table II are first cut estlmates. As future
systems analysis are performed, the values will become more mature. One objec-
tive of the power system studies is to discover those technologies that provide
the greatest leverage; either by possessing significant mass or reliability
advantages, or having a high degree of commonality. Thus, we will be able to
focus our resources on those technologies that have the highest pay off.
13
CRITICAL TECHNOLOGY
CRYOGENIC FLUID MANAGEMENT
AUTOMATED RENDEZVOUS AND DOCKING
AUTONOMOUS ROVERS
MARS AND EARTH AEROCAPTURE
ON-ORBIT ASSEMBLY & CONSTRUCTION
SURFACE EXTRA VEHICULAR ACTIVITY SUITS
SURFACE POWER (INCLUDING 5P-100)
ADVANCED CHEMICAL PROPULSION
NUCLEAR ELECTRIC PROPULSION
IN-SITU PROPELLANT PRODUCTION
ADVANCED LIFE SUPPORT
LEGEND:. O iNDICATES_REQUiRED T_CHNOLOGY
O INDICATES CRITICAL PACING ELEMENT
HUMAN
EXPEDITIOn
TO PHOBOS
O
O
O
HUMAN
EXPEDITION LUNAR
OBSERV.
O
TO MARS
0 0 0
0 0
0 0 0
LUNAR
OUTPOST TO
EARLY MARS
EVOLUTION
O O 0
0
0
0
TABLE I - ASSESSMENT OF PREREQUISITE TECHNOLOGY
,=
14
SYSTEM ELEMENT
PLANETARY UTILITY VEHICLE
PLANETARY MINING VEHICLE
PLANETARY CONSTRUCTION VEHICLE
PLANETARY MANNED EXCURSION
LUNAR OBSERVATORY
LUNAR PROCESSING
LUNAR BASE
MARS OUTPOST
MARS BASE
PHOBO_DEIMOS PROCESSING
CARGO VEHICLE
STAGING NODES
FUEL DEPOT
POWER
1 -2 kW
5- 10 kW
15 kW
3O kW
30 - 50 kW
150 - 300 kW
100 kW
20 kW
40 - 50 kW
1000 kW
5000 kW
TBD
TBD
COMMENT
RECHARGEABLE
RECHARGEABLE/PEAKING
RECHARGEABLE/PEAKING
CONTINUOUS
FULL NIGHT POWER
ELECTRIC/THERMAL
CREW OF EIGHT
40 DAYS
2 YEARS
TABLE II - ESTIMATED EXTRATERRESTRIAL POWER REQUIREMENTS
OF SIGNIFICANT SYSTEM ELEMENTS
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