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A PROPOSED MICROLANDER FOR LOW-COST LUNAR MISSIONS. 1
A PROPOSED MICROLANDER FOR LOW-COST LUNAR
MISSIONS.
J. M. Kruep
1
, W. P. Blase
2
, and V. Olliver
3
1
TransOrbital, Inc., 11826 Federalist Way, # 12, Fairfax, VA 22030, kruep@erols.com.
2
TransOrbital, Inc., 6430 The Parkway, Alexandria, VA 22310, pblase@aol.com.
3
TransOrbital, Inc., 72 Warner Park Avenue, Laingholm, Waitakere, New Zealand, vsop@ihug.co.nz.
Abstract
Microspacecraft using selected off-the-shelf components are becoming more prevalent as universities,
private organizations, the military, and NASA are required to reduce project costs and times
simultaneously. In addition, falling component and launch prices are making microsatellite design,
construction, and flight projects more and more feasible for university aerospace schools and small
governments. After an almost 30 year hiatus, there is a renewed interest in exploring the Earth's
nearest neighbor, the Moon. Clementine and Lunar Prospector paved the way, and also demonstrated
the possibilities of the low-cost microspacecraft approach. Even more missions are planned for the
next decade. These include not only the NASA, the European Space Agency (ESA) and the Japanese
Space Agency but also private concerns. In this paper, a low-cost "microlander" microspacecraft is
described that is capable of carrying small payloads to the lunar surface and providing power and
communications services. The microlander is intended to be a modular, adaptable, common platform
that is suitable for a number of purposes, including both landing missions and orbital missions.
Several possible missions are described, including a mission to the lunar poles to obtain ground-truth
data against which the Lunar Prospector data may be calibrated, and a lunar sample return mission.
Introduction
A micro-spacecraft is one that weighs on the order of 100 kilograms, as compared to the 1000 kg or
more for a traditional communications or earth-surveillance satellite. Typically, they are also low-
budget, specialized craft performing limited tasks. The amateur radio community, in particular the
Amateur Radio Satellite Corporation (AMSAT), has launched over 30 repeater and relay
microsatellites since 1961.
1,2,3
Over the last decade, NASA and the U.S. Air Force have shown increased interest in "smaller,
cheaper, faster" microspacecraft for performing a variety of missions from Earth surveillance, to
flocks of microsatellites acting together to form a synthetic aperture radar, to interplanetary
exploration. Perhaps the most famous microspacecraft of recent time, Clementine, was the first lunar
mission launched by the United States in 20 years, and returned a tremendous amount of data on the
lunar surface.
Microspacecraft typically perform a limited number of tasks, with 1 to 3 instruments or sensors per
craft. However, because they can be constructed relatively inexpensively - especially if a common
"bus" design is used - many of them can be launched in rapid succession. These microspacecraft can
carpet a target with a large number of similar sensors to make up for limitations due to spacecraft size
(or to allow less "hardened" and thus less expensive instruments), or carry a variety of different
sensors.
4
Microspacecraft of the order of 10 kg, employing miniature
sensors and instruments, are uniquely suited for three types of 2
space science missions: missions that require multiple
simultaneous measurements in different locations, missions that
require very high launch energy and high risk missions where
risk may be reduced by replacing a single large and expensive
spacecraft with numerous independent small crafts.
5
This paper describes a lunar lander which is currently under development and is intended to serve as
a common platform for a variety of lunar missions. It has a limited payload and limited lifetime on
the lunar surface, but will cost at least an order of magnitude less than previous landers. Also
described are several missions that can be performed with this platform or adaptations of it.
The Electra Platform
The Electra platform is named for a handmaiden to Artemis, the Greek goddess of the moon, who is
identified as the missing "seventh" sister in the Pleides who fled to Artemis following the fall of Troy.
It is a microspacecraft platform, based largely on proven technology and components. To minimize
costs, it is intended to be launched as a secondary payload on a launch vehicle carrying a commercial
payload. It may also be carried on a variety of launchers, including the reusable launch vehicles
currently under development.
The Electra platform consists of a single bipropellant engine; fuel tanks; attitude control thrusters; an
electronics chassis containing the flight computer, communications equipment, and navigation
sensors; a multi-purpose imaging system; and a frame with landing gear. Figure 1 shows the
spacecraft folded for launch, as it might appear just after ejection from the launcher. During flight,
the landing gear would be extended to landing position and locked, but the photovoltaics and imaging
system would be kept folded.
The imaging system, which is located behind the right-front landing gear as seen in Figure 1, is
positioned so that it can view directly down, or can rotate in elevation over 200 degrees. During
flight, this imaging system serves as a navigation sensor and obtains star, Earth, and Moon images
for attitude determination. During the landing cycle, the imager can view the lunar surface and give
the Earth-bound operators a view of the terrain upon which Electra is landing.
Figure 1 - Electra Platform, folded for launch 3
Figure 2 shows the Electra fully deployed, as it would appear on the lunar surface (with the
photovoltaic panels removed for clarity). The imager and high-gain antenna have been rotated to their
upright positions. The imager sits above the main body of Electra so that panoramic images of the
surface may be obtained from a height.
The hexagonal box in the
figures above is the electronics
chassis. This is derived from a
proven, flight qualified design
developed by One Stop
Satellite Solutions of Ogden,
Utah. The square box is the
payload container. Below these
boxes are the fuel tanks and the
propulsion system. Figure 3
shows the Electra with
photovoltaics unfolded after
landing.
Spacecraft Specifications:
Figure 2 - Electra Platform, unfolded for landing (photovoltaic panels removed for clarity)
Figure 3 - Electra, unfolded after landing 4
Main Propulsion:
Single bipropellant thruster, 250 - 350 N (55-75 lbf) thrust, utilizing high-
purity hydrogen peroxide and RP-1.
Attitude Control:
3-axis stabilized via monopropellant hydrogen peroxide reaction thrusters.
Electronic systems:
Based on off-the-shelf modules developed for the microsatellite industry.
Includes GPS receiver, 3-axis inertial sensors, and on-board computer, and
may also include sun angle sensors and Earth and Moon horizon sensors.
Communications:
C band for command uplink and data downlink. Data downlink at 1
Mbit/sec.
Power:
100 Watts on surface, from deployable photovoltaic panels; 50 Watts
available for payload.
Size:
80 cm (31 inches) H & W, 60 cm (24 inches) D.
45 kg (100 lbs) dry mass including payload, 200 kg (440 lbs) fueled
Propulsion and Reaction Control System
The lander's propulsion system utilizes environmentally benign, or "green", hydrogen peroxide and a
hydrocarbon fuel. These were chosen to promote safety and ease of handling during testing and
launch preparations. The traditional propellants hydrazine (and its variants) and nitrogen tetroxide
(N
2
O
4
) have been in use for decades and are well understood. However, they are both very toxic
materials that require storage and handling under dry nitrogen pads/purges and special facilities and
permits for testing. High purity (85-90%) hydrogen peroxide and RP-1, on the other hand, require
only moderate care during handling, do not require inert atmospheres, can be easily flushed if spilled
during handling, and produce a comparable specific impulse performance.
6,7
The Reaction Control System will utilize monopropellant catalytic-decomposition thrusters fed from
the same hydrogen peroxide tank that feeds the main thrusters. The spacecraft will be fully stabilized
in three axes.
Guidance, Power, Control, and Communications Systems
The electronics systems utilized on board the spacecraft will be based on the proven microsatellite
platform developed by One-Stop-