Boeing-led team to develop guided two-stage system that will compensate for winds
Safer Mars landings are in prospect using a two-stage guided parachute to be developed and tested for NASA by a Boeing-led team.
The autonomously guided parachute will be capable of compensating for wind drift during descent and landing within 4km (2.5 miles) of the target area, at lower impact velocity than possible with the parachutes now used for Mars missions.
"Current Mars parachutes work great for the initial opening in supersonic flow, but do not have the high-drag performance of subsonic parachutes," says John McKinney, principal investigator at Boeing Phantom Works, which is working on the programme with parachute manufacturer Irvin Aerospace.
"We are proposing a two-stage parachute, where the smaller drogue is still supersonic, but it then deploys a much bigger parachute with guidance to compensate for the winds," McKinney says. Whereas traditional ballistic parachutes are susceptible to Martian winds, the subsonic parachute will have an onboard flight control system to compensate for drift during descent.
The guidance system uses three slots around the periphery of the canopy, which are opened and closed by servo-controlled actuators on the spacecraft via control lines running up to the canopy. Already used in Earth-based, pilot-controlled parachutes, the slots generate lateral forces that can be used to steer the parachute.
Under the three-year, $1.5 million NASA contract, Irvin will provide a full-scale Mars parachute with a flight control system, while Boeing will develop the closed-loop wind drift compensation control-law to command the slots.
In flight tests scheduled for mid-2005, two parachutes will be dropped from a balloon at 100,000ft (30,000m), simulating a Mars altitude of 10,000ft. One parachute will be ballistic, while the other will have one open control slot - the aim of this "open-loop" test being to verify the lateral force generated, says McKinney. This data will then be used in development of the control law for a full-size guided parachute test in 2006.
NASA may use the new parachute in a Mars lander technology testbed planned for launch in 2011, says McKinney. In addition to increased landing accuracy, a two-stage supersonic/guided-subsonic parachute could lower the velocity and, therefore, a reduced airbag or retro-rocket system would be adequate for a "soft" Mars landing, he says.
GRAHAM WARWICK / WASHINGTON DC
Source: Flight International
