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Altair
New Altair design.PNG
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 (77,280 lb)
Rocket engines[1]
RCS 445 N (100 lbf)
Ascent Propulsion System
(LOX/LH2) RL-10 derivative x 1:
44.5 kN (4.47 LTf)
Descent Propulsion System
(LOX/LH2) RL-10 derivative x 4:
66.7 kN (6.69 LTf)
Performance
Endurance: 7 days (Sortie missions) Up to 210 days (Outpost missions)
Periselene: surface
Altair spacecraft logo.jpg
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 would be used both for lunar sortie and lunar outpost missions.[2] On February 1, 2010, U.S. President Barack Obama announced a proposal to cancel the Constellation program effective with the U.S. 2011 fiscal year budget.[3]

Contents

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; the name Altair itself is a Latinization of the Arabic الطائر al-ṭā'ir, meaning "The Eagle," "The Bird," or "The Flyer."[4]

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).

Prior to the announcement of the "Altair" name, reports had suggested other names had been considered by NASA.[5][6]

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.[7]

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, the Altair's crew cabin is based on that of a cylinder. Initially a horizontal cylinder, like that of the LM (despite the "boxy" appearance on the outside), current blueprints and computer simulations show the use of a vertical 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 crew module remains in lunar orbit.

Altair will be capable of operating away from Earth (in space and on the lunar surface) for up to 210 Earth days.[8] Altair will also be capable of flying unmanned missions,[8] as had been proposed with LM Truck concept during the Apollo Applications Program. Mission planners will be able to choose among three distinct mission modes for Altair:[8]

  1. crewed sortie mode
  2. crewed outpost mode (with no airlock)
  3. uncrewed cargo mode, capable of transporting up to 15 metric tons to the lunar surface

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 potentially 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 extra-vehicular activity, the airlock will allow a crew member with a malfunctioning spacesuit to quickly return to the Altair spacecraft without having to terminate the entire EVA, and allow the landing party to complete most of their tasks during their 7-day lunar stay. Also, the airlock will remain as part of the Altair's descent stage, allowing NASA to utilize the airlock as a component of the Lunar Outpost.

Because the Ares V will have a diameter of 33 ft and height of 49 ft (including landing gear), the landers will necessarily have to be designed to retract so as to fit within the Ares V's payload shroud.

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), using data acquired by advanced unmanned lunar orbiting spacecraft, and new "glass cockpit" and Boeing 787-based computer system identical to that on the Orion spacecraft.

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Engines

Altair will use current cryogenic technologies for the descent stages and hypergolic technologies for the ascent stage. The Apollo LM, as advanced in both computer and engineering technology in its day, used hypergolic fuels in both of its stages, chemicals that combust on contact with each other, requiring no ignition mechanism and allowing an indefinite storage period. Both the cryogenic and hypergolic systems, like that of the Apollo LM, will be forced-fed using high-pressure helium, eliminating the need for malfunction-prone pumps utilized in most rocket technology.

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 bringing it and the Orion spacecraft into lunar orbit, as the Orion spacecraft's onboard Aerojet AJ-10 rocket 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 a modified RL-10 engine (currently in use on the upper stage of the Delta IV rocket and Centaur upper stage of the Atlas V rocket), burning liquid hydrogen (LH2) and liquid oxygen (LOX) for the descent phase. A single AJ-10 rocket engine, like that on the Orion, will power the ascent stage.

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 and hypergolic systems 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 (LEO) 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.

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.[9]

References

External links


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