A NASA Ames team is studying a novel means of retrieving the Space Shuttle's solid rocket boosters (SRBs). It would use an oblique wing to enable the boosters to glide back autonomously to Kennedy Space Center for a controlled landing rather than splash down into the ocean for recovery.

The study is an alternative to the fly-back booster options being evaluated by Boeing and Lockheed Martin under contract to NASA Marshall Space Center. Dr Steve Smith, the NASA Ames team leader, believes the glideback option could save up to 13,600kg (30,000lb) a booster in terms of the equivalent fuel load and engine weight. Given the two current SRBs, this would save "a Space Shuttle payload just in fly-back fuel", he says.

The SRBs normally burn out and separate from the Shuttle 42km downrange at 252,000ft/min (1,280m/s). "That's going Mach 4 in the wrong direction," says Smith. The study asks: "Can it be turned, can you glide back that far?" The answer, according to preliminary studies, is yes, he adds.

Smith believes the wing-equipped SRBs could glide in from a turnback range of 280km and "make it home with about 2,500ft [760m] to spare".

The 37m-span wing would be mounted flush with the casing of the 45.5m-long booster for lift-off and would begin unsweeping at about M3 and an altitude of 80,000-90,000ft (24,400-27,450m), a few seconds after separation.

The sweep angle would briefly stabilise at around 70¼ before opening up to 65¼ for the pull-up manoeuvre at M1.7. On the return leg, it would decrease sweep from 45¼ to 30¼ as the SRB decelerates through M1. Sweep angle would quickly be reduced to 0¼ as the wing extended for maximum lift for the long glide home.

Source: Flight International