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Altair (spacecraft)

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This article is about the Lunar lander, for the communication satellites, see Altair (satellite)
Altair

Artist impression of the Altair lander on the surface of the moon. (NASA)
Description
Role: Lunar landing
Crew: 4
Dimensions
Height: 9.7 m (32 ft)
Diameter: 7.5 m (25 ft)
Landing gear span: 14.8 m (49 ft)
Volume: 31.8 m3 (1,120 cu ft)
Masses
Ascent module: 10,809 kg (23,830 lb)
Descent module: 35,055 kg (77,283 lb)
Rocket engines[1]
RCS 445 N (100 lbf)
Ascent Propulsion System
(LOX/LH2) RL-10 derivative x 1:		 44.5 kN (4.47 long tons-force)
Descent Propulsion System
(LOX/LH2) RL-10 derivative x 4:		 66.7 kN (6.69 long tons-force)
Performance
Endurance: 7 days (Sortie missions) Up to 210 days (Outpost missions)
Periselene: surface

Altair logo
Altair

The Altair spacecraft, previously known as the Lunar Surface Access Module or LSAM, is the planned lander spacecraft component of NASA's Project Constellation, which astronauts are to use for landings on the Moon intended to begin around 2019. Altair spacecraft will be used both for lunar sortie and lunar outpost missions.[2]

Name

On December 13, 2007, NASA's Lunar Surface Access Module was retitled "Altair", after the 12th brightest star in the northern hemisphere's night sky, Altair in the constellation Aquila. In Latin, "Aquila" means Eagle, providing a connection to the first crewed lunar landing, Apollo 11's Eagle.[3]

The landers used on the Apollo missions were called Lunar Modules, and often (imprecisely) referred to as Lunar Landers, Lunar Excursion Modules or LEMs (Lunar Excursion Module was the original designation of the LM, until changed by NASA due to public perception that "excursion" meant going on a picnic).[citation needed]

Prior to the announcement of the "Altair" name, reports had suggested other names had been considered by NASA.[4][5]

Description

NASA is currently developing conceptual designs for Altair. As of 2008 no Altair spacecraft have been built — plans call for a first landing on the Moon in 2018.[6]

Like the Apollo Lunar Module (LM), Altair is envisioned as having two stages. The descent stage will house the majority of the fuel, power supplies, and breathing oxygen for the crew. The ascent stage will house the astronauts, life-support equipment, and fuel for the ascent stage motor and steering rockets. Like the Apollo LM, Altair's crew module is based on a sideways cylinder.[citation needed] Unlike its two-man Apollo ancestor, Altair will carry the entire four person crew to the surface, while the temporarily unoccupied Orion spacecraft remains in lunar orbit. Altair will also be used to fly unmanned missions,[citation needed] as had been proposed with LM Truck concept during the Apollo Applications Program.

Altair, like the LM, will have two hatches – one on top for docking and internal transfer between Altair and Orion, and a main hatch for accessing the lunar surface. Unlike the Apollo LM, Altair will have an airlock similar to those on the Space Shuttle and the International Space Station between the cabin and main hatch. The airlock will allow the astronauts to don and doff their spacesuits without tracking hazardous moon dust into the main cabin and allows the vehicle to retain its internal pressure.[citation needed] Unlike the Apollo LM, in which the entire cabin was depressurized during spacewalks, the airlock will allow a crew member with a malfunctioning spacesuit to quickly return to the Altair spacecraft without having to terminate the entire lunar spacewalk, and allow the landing party to complete most of their tasks during their 7-day lunar stay.

The spacecraft will also include an improved 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" and Boeing 787-based computer system identical to that on the Orion spacecraft.

Engines

Altair will use current cryogenic fuel technologies for the descent and ascent stages. The Apollo LM, 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 a polar (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 are insufficient to brake the Orion/Altair 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 upper stage of the Delta IV rocket and 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 Orion.

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. The Sabatier Reactor could be used to convert the carbon dioxide (CO2) found on Mars into methane, using either found or transported hydrogen, a catalyst, and a source of heat. Cost overruns and immature LOX/LCH4 rocket technology have forced NASA to stick with cryogenic fuel for the near future, although later variants of Altair will serve as testbeds for methane rockets and Sabatier reactors after a permanent lunar base is established.

On-orbit assembly

Because of the spacecraft's size and weight, Altair, 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 Altair in LEO, the crew will then configure the Orion/Altair for the journey to the Moon. If an unmanned Altair 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 Altair to the Moon.

Proposed flights

Offices and development

The development of Altair will be managed by the Constellation Lunar Lander Project Office at Johnson Space Center (JSC). JSC is working directly with Apollo astronauts, various industry suppliers and universities to develop the architecture for Altair. In conjunction with early development a mockup or testbed will be developed at JSC to study/develop specialized subsystems and other design considerations. Northrop Grumman, who built the Apollo Lunar Module, has been contracted to help the project office develop the system concept.[7] The University of Colorado at Boulder's Lunar-MARS program.[8] This project was featured on nation-wide news broadcasts in May 2007.[9]

References

  1. ^ "NASA's Exploration Systems Architecture Study". nasa.gov. Retrieved 2007-11-13.
  2. ^ "Lunar Orbit Insertion Targeting and Associated Outbound Mission Design for Lunar Sortie Missions" (PDF). NASA. 2007.
  3. ^ "NASA names next-gen lunar lander Altair". collectspace.com. Retrieved 2008-02-06.
  4. ^ "NASA to name moonlander after Greek goddess Artemis". flightglobal.com. Retrieved 2006-10-03.
  5. ^ "NASA lunar lander design plans revealed". flightglobal.com. Retrieved 2007-07-17.
  6. ^ "NASA Chooses "Altair" as Name for Astronauts' Lunar Lander". NASA. 2007-12-18.
  7. ^ "Northrop Grumman Helps NASA Shape Plans for Affordable Lunar Lander". irconnect.com. Retrieved 2007-07-17.
  8. ^ "CU Lunar Module and Analog Research Station (LunarMARS) Program". colorado.edu. Retrieved 2008-02-06.
  9. ^ "CU Students Build Mock Lunar Lander for 2018 Mission to Moon". cbs4denver.com. Retrieved 2007-05-02.
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