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 NASA’s 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.
Lunar Quest
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 moon’s 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 NASA’s 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 unprecedented detail.
Also read: Minotaur 4 Suborbital Launch
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.
Boeing’s Proposal
Space Launch System Configurations for Lunar Landing Missions (Boeing)
In late 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 attempted.
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.
Author:
by Ed Kyle, 05/06/2012
