NASA has reduced the total mass (weight of the body on Earth) of the Ares I booster so that it can successfully send the Orion spacecraft further into a preliminary trajectory about the Earth.

Ares I consists of a single five-segment ATK (Alliant Tech Systems) Thiokol solid rocket booster (SRB), which was designed based on the four-segment SRBs of the Space Shuttle program, and one liquid-fueled upper stage (second stage) rocket powered by a single J-2X rocket engine, which originated from the Saturn series of rockets (from the Apollo program).

During the first couple of minutes after launch, the first stage booster rocket will power the Orion spacecraft to an altitude of about 30 miles above the Earth. It will then separate from the rest of the spacecraft and fall back to the ocean below to be later recovered. Then, the second stage liquid oxygen/liquid hydrogen fueled J-2X engine ignites and takes the Orion and its crewmembers to an elliptical orbit (around 85 miles) about the Earth.

After the second-stage separates, Orion’s propulsion system, which is contained within its service module, powers the spacecraft to a circular orbit (nominally about 185 miles) above the Earth. While in orbit, the Crew Module (CM) and the Service Module (SM)—together called the Orion Crew and Service Module (CSM)—will rendezvous and dock with the ISS, or later in its mission agenda, with lunar craft in order to journey to the Moon.

For all of this to happen, according to the NASAspaceflight.com article “Orion weight saving refinements continue - focus on ISS access”, Orion has been reduced in weight—when traveling to the ISS—to "10,973 pounds (4,977 kilograms)", which is less than what it will weigh when performing later missions to the Moon.

NASASpaceFlight writers Chris Bergin and David Harris state within the article that Orion’s engines, at this newly defined weight for ISS missions, will produce about “7,300 pounds (3,311 kilograms) of thrust” using hypergolic (spontaneously igniting when in contact) propellants: nitrogen tetroxide (N₂0₄) and monomethythydrazine (MMH).

NASA is attempting to meet its own self-imposed deadline of September 2012 for the first mission of the Orion series as a “full stack, unmanned orbital flight”, followed with the “first manned orbital flight” in October 2013.

Before this happens, however, NASA has scheduled a test launch in April 2009 of an Ares I booster rocket, which will consist of its five-segment booster rocket (with the fifth segment empty) and a non-functioning upper stage rocket. This flight will be a sub-orbit flight to test the first-stage Ares I system. Other unmanned ascent abort system tests will be performed in 2010 and 2011.

For additional information about the next-generation NASA Orion spacecraft and its Constellation program, go to: http://www.nasa.gov/mission_pages/constellation/orion/index.html.

The complete NASAspaceflight.com article is found at: http://www.nasaspaceflight.com/content/?cid=5167.

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