Lunar Surface Access Module

From Wikipedia, the free encyclopedia

The LSAM launches its ascent stage to return the astronauts to Lunar Orbit.

The Lunar Surface Access Module (LSAM) is the planned American moon landing vehicle that will allow astronauts to land there around 2020 as part of NASA's Project Constellation.

1 Name
2 Description
- 2.1 Engines
3 On-Orbit Assembly
4 References
5 External links

[edit] Name

The LSAM is currently expected to be named "Artemis" after the Greek goddess of The Moon, however no official announcement has been made.^[1]

[edit] Description

The LSAM, which is similar in design to (but much larger than) the Apollo Lunar Module (LM), will consist of two stages: a descent stage, which will house the majority of the fuel, power supplies, and breathing oxygen for the crew, and an ascent stage, which will house the astronauts, life-support equipment, and fuel for the ascent stage motor and steering rockets. Like the Apollo LM, the LSAM's crew module is based on a sideways cylinder, but unlike its two-man Apollo ancestor, the LSAM is designed to carry the entire four-man mission crew to the surface while the Orion Spacecraft remains unmanned in lunar orbit. It can also be flown unmanned, similar in the Apollo Applications Program's LM Truck concept, but without having to fly a manned Orion spacecraft out to the Moon (thus the unmanned LSAM would be flown similar to that of the unmanned aerial drones used by the U.S. Air Force).

The LSAM, like the LM, will have two hatches – one located on top for docking and internal transfer between the LSAM and the Orion, and a main hatch for going out to the lunar surface. Unlike the Apollo LM, the LSAM will have an airlock similar those on the Space Shuttle and International Space Station between the cabin and main hatch. The airlock will allow the astronauts to put on and take off their spacesuits without trailing hazardous moon dust into the main cabin, as well as allowing the vehicle to retain its internal pressure – the Apollo LM required the entire cabin to be fully depressurized before a moon walk. The airlock would allow an astronaut with a malfunctioning spacesuit to re-enter the vehicle without the entire crew having to end their moon walk.

The spacecraft will also include a miniature camping-style toilet, similar to the unit now used on the ISS and the Russian Soyuz spacecraft; a food warmer to eliminate the "cold soup" menu used during Apollo missions; a laser-guided distance measurement system (with radar backup); and new "glass cockpit" that will be identical to that used on the Orion spacecraft.

[edit] Engines

It will use current cryogenic fuel technologies for the descent and ascent stages. The Apollo Lunar Module, advanced technology in its day, used hypergolic fuels, chemicals that combust on contact with each other, requiring no ignition mechanism and allowing an indefinite storage period. The cryogenic fuels, like the hypergolic fuels planned for the Orion spacecraft, will be pressure-fed using helium gas, eliminating malfunction-prone pumps.

Mission requirements oblige the vehicle to be able to descend from an equatorial (or high-inclination) lunar orbit to a polar landing site, along with braking it and the Orion spacecraft into lunar orbit, as the Orion spacecraft's onboard Delta II-based engine and the amount of fuel it carries is insufficient to break the Orion/LSAM stack into lunar orbit (also crucial if it is flown unmanned without an Orion crew). The new lander will be powered by four modified RL-10 engines (currently in use on the Centaur second stage of the Atlas V rocket), burning liquid hydrogen (LH₂) and liquid oxygen (LOX) for the descent phase, and using a single RL-10 for the trip back to the CEV.

Originally, NASA wanted to power the ascent stage using LOX and liquid methane (LCH₄); as future missions to Mars would require the astronauts to live on the planet, using technologies (such as the Sabatier Reactor to convert the carbon dioxide (CO₂) found on the planet into methane (using either found or transported hydrogen), but cost overruns and infant LOX/LCH₄ rocket technology has forced NASA to revert to current cryogenic technologies, although future variants will have LOX/LCH₄ technologies to allow the LSAM to serve as a testbed for such technologies after a permanent lunar base is established.

[edit] On-Orbit Assembly

Because of the spacecraft's size and weight, the LSAM, and its associated Earth Departure Stage, will be launched into a Low-Earth Orbit using the heavy-lift Ares V launch vehicle, followed by a separate launch of an Orion spacecraft lifted by an Ares I. After rendezvous and docking with the LSAM in LEO, the crew will then configure the Orion/LSAM combination, followed by the firing of the Earth Departure Stage to propel the two spacecraft to the Moon. If an unmanned LSAM is flown, the spacecraft will be checked out after the first EDS firing in LEO (similar to that of the Apollo "Parking Orbit") before the second firing of the EDS propels the unmanned LSAM to the Moon.