Saturday, October 8, 2011

NASA to Begin Competition for SLS Boosters

An artist's concept of the Space Launch System. Image source: NASA.

Aviation Week reports that, "NASA plans to open a competition in December for multiple, 30-month contracts to study strap-on booster upgrades for the planned heavy-lift Space Launch System (SLS), including an upgrade for the five-segment, solid-fuel strap-ons baselined as the initial boosters for the big new rocket."

One challenge for NASA engineers will be to design an interface that can link different booster types to the SLS core stage, according to William Gerstenmaier, associate administrator for human exploration and operations. The SLS will be the vehicle NASA uses to send humans beyond low Earth orbit.

“Our vision is we’ll have an interface that’s generic, and we’ll be able to carry potentially different boosters and change them out as needed,” Gerstenmaier told a session of the International Astronautical Congress [in Cape Town, South Africa] Thursday. “So we could go compete in the future, maybe downsize if something’s easier for a mission that requires less thrust. We have some variability there, so if we do our job right, we’ll have the ability to change the boosters that sit on the side. That’s our ultimate goal. We’re not going to pick one.”

The article quotes Gerstenmaier as saying only the first two SLS flights will use a five-segment solid rocket booster design.

“It turns out that to get to the 130 metric tons, we’re going to have to redesign the five-segment booster as well,” Gerstenmaier says. “We have to go to potentially a composite case, away from our steel case to save some weight, and we might need to make a propellant change to use the more energetic propellant that sits in the solid rocket motor. So even if we go continuous solids, we’re going to have to make a pretty significant change to the solid-rocket booster segment.”

The solid rocket motors for the early flights would be built by Utah's ATK. Utah Senator Orrin Hatch sent a letter to NASA Administrator Charles Bolden in August demanding that the SLS use only solids (implicitly built in Utah) claiming the SLS design legislation written by the Senate space subcommittee in 2010 required solids. He also claimed that "expert advice" concluded "the only way to realistically meet these requirements" was to use solids. The letter was co-signed by four other Senators.

So it remains to be seen how much freedom NASA will have from Congress to select a vendor other than ATK.

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