As NASA Eyes Common Upper Stage, Solar Probe Mission Building Its Own

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WASHINGTON — Even as NASA studies adding a common kick stage to its rocket catalog — to give the medium- and intermediate-class rockets it already offers an adrenaline shot for high-energy launches — one flagship science mission is forging ahead with development of its own new upper stage.

The mission, which still must be formally approved by NASA in a review scheduled for early 2014, is Solar Probe Plus. The flagship observatory, which NASA estimated in its 2014 budget request will cost $1.2 billion to $1.4 billion to build, launch and operate, is slated to lift off for a seven-year sun-watching mission in 2018 — the same time frame Orbital Sciences Corp. and Aerojet Rocketdyne are using as the notional delivery date for a conceptual upper stage whose development they are studying for NASA with a pair of contracts, worth about $300,000 each, awarded in late September.

The results of the study are due to NASA by late May. Should the agency elect to send either company’s study concept into production, it is conceivable, although far from a foregone conclusion, that Solar Probe Plus — a heavily shielded spacecraft engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., are designing to approach within 6 million kilometers of the sun’s surface  — might use the new upper stage. 

“That’s not the plan,” James Norman, NASA’s director of launch services, said in a Nov. 13 interview at NASA headquarters here. “But it is one possible outcome.”

The point of the study, Norman told SpaceNews, is to relieve mission planners who need one of responsibility for finding their own kick stage. A common kick stage might also create more competition by giving NASA more options when soliciting launch service bids for missions that need a medium- or intermediate-class rocket.

Norman said these rockets include Orbital Sciences’ Antares, Space Exploration Technologies Corp.’s Falcon 9 and United Launch Alliance’s Atlas 5.

“If [we] can put the payload that’s a little short, in terms of what it needs to go somewhere, with this upper stage … we’re enabling competition,” Norman said.

Currently, any NASA science mission that needs more power than agency-approved rockets provide in a stock configuration have to purchase their own upper stage. For example, the APL-led New Horizons mission launched to Pluto in 2006 on an Atlas 5 equipped with a Centaur liquid-fueled upper stage supplemented by an ATK Star 48BV solid-motor kick stage that put the 480-kilogram probe on its trajectory toward a gravity-assist flyby of Jupiter.

Solar Probe Plus was going to use the New Horizons launch rig, but the heliophysics spacecraft, expected to tip the scales at 665 kilograms, has outgrown that configuration and cannot get to its intended orbit without an added boost. As it is, the mission will have to perform seven gravity-assist flybys of Venus to reach its destination.

“To meet the launch energy requirement, the Solar Probe Plus team had to upgrade the upper stage motor,” Andrew Driesman, the mission’s project manager at APL, wrote in a Nov. 13 email.

To that end, APL has been paying ATK Missile Products of Elkton, Md., to work on a derivative of the motor that powered New Horizons’ third stage. Work on the new motor, known as Star 48 GXV, has been ongoing since 2011, and ATK plans to test fire the motor Nov. 26 in Elkton, Driesman said. The motor is being designed as a third stage for the Atlas 5 551 rocket, which features a single-engine Centaur. However, the mission’s launch vehicle will not be officially selected until some time next year, after Solar Probe Plus is confirmed to proceed into development by NASA’s Science Mission Directorate.

Because the Solar Probe Plus team is gearing up to present its mission to higher-ups in NASA’s Science Mission Directorate, it cannot halt development on its ATK-powered upper stage simply because the Launch Services Program is considering developing a common kick stage.

Authorized to proceed in 2009 and scheduled for a preliminary design review in January, Solar Probe Plus will reach a milestone known as Key Decision Point C sometime between March and June, according to NASA’s 2014 budget request. That milestone, which involves peer review and sign off from NASA headquarters, clears the way for spacecraft development to begin in earnest.

Once the mission passes Key Decision Point C, NASA also will have to make a decision about Solar Probe Plus’ launcher. A new common upper stage could be an option for Solar Probe Plus if the NASA Launch Services Program’s rocket buyers at Kennedy Space Center, Fla., like what they see from the studies Aerojet and Orbital are working on.

During its seven-year mission, Solar Probe Plus will measure blasts of charged particles, or solar winds, emanating from the star’s corona. These charged particles can disrupt sensitive electronic equipment in space and on Earth’s surface. Sending a dedicated probe to the sun was identified as the top priority in a 10-year heliophysics roadmap, “The Sun to the Earth — and Beyond,” published in 2003 by the National Research Council.

 

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