NASA's Return to the Moon
by Ed Kyle, 05/06/2012
JSC's Lander Prototype Morpheus Ground Test, April,
After decades of ignoring Earth's companion, and even in
the wake of President Obama's cancellation of its manned lunar landing program, NASA has
managed to once again focus resources on the Earth's moon.
After a decade of inactivity, NASA has, within the past
two years, sent three spacecraft into lunar orbit (LRO, GRAIL A, and GRAIL B), and crashed
one (LCROSS) into its surface. A fourth spacecraft (LADEE) is being assembled for a
2013 launch. It is the busiest period of unmanned lunar exploration for NASA since
the days of Ranger, Lunar Orbiter, and Surveyor.
At NASAs Johnson and Marshall Space Flight
Centers, teams of engineers have designed, built, and in recent months even tested robotic
lunar lander concept demonstratiors. More tests are planned this year. At
Boeing's Phantom Works a creative proposal to return astronauts to the lunar surface has
been devised, presented, and garnered support.
Space Launch System, a super-rocket in obvious need of a
specific mission, will, according to current plans, launch spacecraft toward lunar
swingbys during both its first unmanned test in 2017 and its first crewed mission in 2021.
The obvious next step would be to return humans to the Moon's vicinity for longer
stays, and then, possibly, return them to the lunar surface itself.
LADEE Illustration (NASA)
NASA's newly named Lunar Quest Program includes both
flight missions and research efforts. Managed by Marshall Space Flight Center, Lunar Quest
encompasses Lunar Reconnaissance Orbiter (LRO), Lunar Atmosphere Dust Environment Explorer
(LADEE), and Robotic Lunar Lander (RLL).
Lunar Reconnaissance Orbiter (LRO), launched on June 18,
2009 along with the Lunar Crater Observation and Sensing Satellite (LCROSS), is currently
orbiting and mapping the Moon. LCROSS was deliberately crashed into the Moon as part
of a search for polar water ice.
LADEE, planned for launch in 2013, will measure the
moons atmosphere and dust environment. This 383 kg spacecraft will be launched
by a Minotaur 5 from Wallops Island, Virginia. It will use a Space Systems/Loral
propulsion system adapted from commercial communication satellites.
The Robotic Lunar Lander (RLL) program, managed jointly
with the John Hopkins Applied Physics Laboratory, includes development of a generation of
smart robotic landers that could land on the Moon and on near-Earth asteroids. In
2011, NASA performed a series of robotic lander prototype tests at Redstone Test Center on
the U.S. Army Redstone Arsenal in Huntsville, Alabama. The Robotic Lander
Development Project prototype, named "Mighty Eagle", hovered at heights up to
100 feet, and for durations of up to 30 seconds, before landing.
Mighty Eagle Hover Test, November 2011 (MSFC)
Mighty Eagle, a three-legged prototype, weighed 317 kg,
stood 1.2 meters and was 2.4 meters in diameter. It was fueled with 90 percent
hydrogen peroxide and used 16 thrusters. Contractors on the project included Science
Applications International Corporation, Dynetics Corp., Teledyne Brown Engineering Inc.,
and Millennium Engineering and Integration Company, all of Huntsville.
A second lander prototype named "Morpheus" was
developed and is being tested by NASAs Johnson Space Center, with tethered test
flights taking place during the Spring of 2012. Like MightyEagle, Morpheus is a full
spacecraft, with avionics, software, guidance, navigation and control, power systems,
structures, propulsion, and instrumentation. The lander's propellant combination was
liquid oxygen and methane, a useful combination because it can be stored in space longer
than liquid hydrogen, but offers better performance than standard hypergolic propellants.
Methane could be made from lunar ice or produced in other ways.
NASA's Jet Propulsion Laboratory in Pasadena, Calif.,
manages the GRAIL (Gravity Recovery And Interior Laboratory) mission, which does not
directly fall within the Lunar Quest program. GRAIL, consisting of a twin pair of
satellites built by Lockheed Martin, was launched by a Delta 2 in 2011 and is currently
manevering into a low lunar orbit. The satellites will map lunar gravity in
Space Launch System and the Moon
NASA's Space Launch System, with its Orion spacecraft,
has yet to be assigned a specific long term mission. The only two announced launches
include an unmanned 2017 test flight, which will send an Orion around the Moon, and a
manned repeat flight in 2021.
Groups within NASA are working on mission plans for the
new rocket, which will be able to lift more than 70 tonnes (perhaps up to 90 tonnes) to
low earth orbit in its initial Block 1 form. One plan being seriously considered is
a "human-tended waypoint" near the far side of the moon, at Earth-Moon Libration
Point 2 (EML-2). Earth-Moon Libration, or Lagrangian, points are where the combined
gravitational pull of Earth and Moon roughly balance each other out, creating a spot where
spacecraft could maintain their relative position while using little propellant.
EML-2 could serve as a station for exploring the lunar
far side, which has never been visited by any landings. Far side geography is much
different than the near side. Some theories suggest that the far side may have much
older rocks than the near side. Rock samples would test such theories, which have
implications for theories of how the Moon and the Earth were created.
Launch System Configurations for Lunar Landing Missions (Boeing)
2011, Boeing's Skunk Works proposed a method for using an EML gateway, and a new reusable
lunar lander, to return astronauts to the lunar surface. A reusable lander was
possible because of the EMLgateway, which could efficiently serve as a propellant depot.
The lander would be fueled by LOX and methane and would only weigh 15 tonnes when
loaded with 8.6 tonnes of propellant. This compares with Project Apollo's
14.7 tonne Lunar Module and Project Constellation's 45 tonne Altair lander.
Boeing's proposal called for use of a
highly modified Delta 4 Heavy cryogenic upper stage, outfitted with auxiliary methane
refueling tanks, to serve as a "crasher" descent stage for the lunar lander.
The crasher stage, which could carry up to 40 tonnes of propellant, would perform
most of the descent burn, separating only shortly before the terminal descent phase.
This would minimize the descent propellant required to be burned by the lander,
allowing the complete lander to ascend and be reused. Only the lander and the
descent stage would depart the EML gateway. Orion would remain at the gateway during
the landing mission.
In order for this concept to work, a
new cryogenic second stage would need to be added to the Block 1 SLS to boost a fully
fueled descent stage and Orion spacecraft to the EML gateway for each landing mission.
After the gateway and lander were positioned, this would allow a lunar landing to
be performed using only one SLS launch. Only Methane and LOX would need to be
supplied to the gateway for refueling purposes, since all necessary liquid hydrogen would
be carried and used by the descent (third) stage on each mission.
Drawings shown during a November 2011
presentation showed an SLS with an 8.4 meter diameter second stage topped by either the
descent (third) stage or a lander, with an Orion spacecraft always at the top. The
descent (third) stage would use a 5.5 meter diameter liquid hydrogen tank from the Ares I
program, replacing the Delta 4 Heavy's five meter tank. A similar 5.5 meter tank
would carry LOX for the second stage.
Boeing noted that the gateway could
serve as a refueling and control center for robotic landers before human landings were
Use of an EML gateway offers
continuous launch windows for lunar landing missions, a benefit compared to narrow
bi-monthly opportunities offered by a low lunar orbit station. The tradeoff would be
that an EML gateway mission would require more delta-v (10,480 m/s) than a low lunar orbit
gateway mission (8,951 m/s).
Boeing's proposal had supporters and
detractors, but the general idea of an early lunar focus for the SLS/Orion program seems,
in general, to be gaining traction. Such a plan would provide a strong mission for
the program, one that would likely garner Congressional, and likely public, support.
Planning groups are studying these,
and other, plans. NASA may soon decide on a future that once again includes the
Moon Mission Concept with Reusable Lander,
Ben Donahue, Sr. Principal Engineer, Boeing Skunk Works, Global Exploration Workshop,
SPACE LAUNCH REPORT
by Ed Kyle