Original URL: http://www.theregister.co.uk/2009/11/24/nasa_robo_rocket_plane_for_mars/

NASA plans robot rocket aeroplane to fly above Mars

To join nuclear laser tank. Mars defends, actually

By Lewis Page

Posted in Science, 24th November 2009 13:36 GMT

NASA intends to build a robot rocketplane the size of a light aircraft and send it across space to fly the skies of Mars: and the space agency wants help in building it.

Concept of the ARES droid-plane unfurling in the skies above Mars. Credit: NASA Langley

Not quite so impressed with our tripod walker machines now, are we?

The droid aeroplane is known, slightly confusingly, as ARES (Aerial Regional-scale Environmental Surveyor), the same moniker as NASA's proposed new generation of launch rockets. But this ARES is different.

It would be launched from Earth - probably atop a Delta II rocket stack - and fly to Mars packaged in an "aeroshell" re-entry capsule. Having entered the thin Martian atmosphere, the aeroshell would open and parachutes would drag out the folded-up aeroplane. Wings and tail would pop into place and the propulsion system (a liquid bipropellant rocket) would fire up. Meanwhile the carrier spacecraft, having dropped the aeroshell into the atmosphere, would lift into a "flyby" trajectory above the planet.

The plane would then stabilise in flight above the red planet a mile up for approximately an hour and a quarter, scanning the atmosphere and terrain over as much as 600km before running out of juice. The idea is that the ARES would give much more detailed readings than an orbiter, but cover much more ground than ground rovers can. Data would be relayed back to Earth via the carrier spacecraft.

The Mars-plane idea has been kicking around at NASA for years - it was thought at one point that that it might launch as soon as 2007, but that never happened. Last week, however, the agency issued a "teaming opportunity" in which companies or designers might lend boffins at the Langley space centre a hand.

The idea would be to put forward revised ARES Mars-plane plans for consideration as a "Discovery" mission. The Discovery missions will focus on exploration of planets in the solar system, and are intended to be relatively low cost and quick to implement.

So what exactly does NASA need help with?

Specifically, NASA is looking for help with:

(1) The ARES Science Team.

(2) ARES Education and Public Outreach (E/PO) Team.

(3) Design and development of the aerial platform structures and mechanisms subsystem including the composite airframe, associated hinging and latching mechanisms, and control surfaces.

(4) Design and development of the liquid rocket propulsion subsystem for the aerial platform.

(5) Design and development of the command and data handling, flight software, and the navigation sensors (only for entry and flight over Mars).

(6) Design and development of the telecommunications subsystem for the aerial platform and entry system.

(7) Design and development of two complete cameras.

Or as far as we can see, NASA would like someone else to help with pretty much everything except the spacecraft and aeroshell bits, presumably fairly closely modelled on those used in previous Mars lander missions.

That said, the space agency has evidently made its mind up about propulsion, plumping firmly for the bipropellant rocket. According to this pdf other options were considered - fuel cells, batteries, different kinds of combustion engines. Though some offered greater range and/or endurance, they were mostly assessed as requiring massive development effort (especially on propellers able to operate in the thin atmosphere of Mars) and associated risks of failure.

One thing which doesn't seem to have been considered is the use of nuclear power, though NASA has specifically stated that Advanced Stirling Radioisotope Generators (ASRGs) can be used in Discovery missions - another candidate, the proposed robot windjammer intended to sail the patio-gas seas of Titan, moon of Saturn, will employ an ASRG.

There is 63kg available in the ARES airframe for fuel and propulsion: this could permit three ASRGs to be carried, offering 450 watts of output. That's not much power - a bit over half a horsepower - but on the other hand the ARES apparently requires just 40 newtons' poke to push it along, a mere 8 or 9 pounds of thrust in Earthly terms. Model aircraft in Earth's atmosphere can achieve 3 or 4 pounds of thrust at 3-400 watts. Perhaps the bigwigs of NASA could do better, especially as it might be possible to lighten the ASRGs by removing some or all of the electric generator hardware.

If it were possible, that would mean an ARES sky-cruiser able to fly for as long as 14 years rather than just 70 minutes or so, and prowl much of the surface of the fourth planet. This kind of long endurance and (relatively) high power output is the reason that the planned "Curiosity"/Mars Science Laboratory ground rover - to feature a laser capable of vaporising rock - is also to be nuclear powered.

That's speculation, however, and the NASA studies to date make it clear that they've decided on the tried-and-true bipropellant option. It may not even be possible to design a propeller to work in the thin atmosphere of Mars, or not until more is known about it.

The ARES Mars-plane is still a pretty exciting idea, though, even with flight endurance of only an hour. If we had a vote, we'd be voting for it to make the Discovery cut.

There's more on the plans here, and the NASA teaming opportunity is here. ®