[X] My Assistant

[Guest_Zvezdichko_*]

I read a very interesting article about the problems when it comes to big landers on the Red Planet ( including Mars Sample Return and manned Mars landers ).

http://www.universetoday.com/2007/07/17/th...the-red-planet/

Some quotes:

The major conclusion that came from the session was that no one has yet figured out how to safely get large masses from speeds of entry and orbit down to the surface of Mars. "We call it the Supersonic Transition Problem," said Manning. "Unique to Mars, there is a velocity-altitude gap below Mach 5. The gap is between the delivery capability of large entry systems at Mars and the capability of super-and sub-sonic decelerator technologies to get below the speed of sound."
Plainly put, with our current capabilities, a large, heavy vehicle, streaking through Mars' thin, volatile atmosphere only has about ninety seconds to slow from Mach 5 to under Mach 1, change and re-orient itself from a being a spacecraft to a lander, deploy parachutes to slow down further, then use thrusters to translate to the landing site and finally, gently touch down.

Apollo and Soyuz capsules and the proposed Crew Exploration Vehicle (CEV) will all decelerate to less than Mach 1 at about twenty kilometers above the ground just by skimming through Earth's luxuriously thick atmosphere and using a heat shield.

then:

Parachutes can only be opened at speeds less than Mach 2, and a heavy spacecraft on Mars would never go that slow by using just a heat shield. "And there are no parachutes that you could use to slow this vehicle down,��? said Manning. "That's it. You can't land a CEV on Mars unless you don't mind it being a crater on the surface."

If what's said here is true, we don't have any chance to land in a way we know - using a standart heat shield, parachute or landing thrusters.
That "Hypercone" concept is interesting and surely could be integrated for a Mars Sample Return mission, but what about a human landing mission? Wouldn't this be a challenge even to be launched with the proposed rockets like Ares 5?

[tasp]

Maybe look at the problem bass-ackwards??

Design an aircraft that could take off from the Martian surface and accelerate to Mach 5 (to an appropriate altitude) and see if that same aircraft could then land. If so, have the re-entry vehicle reconfigure itself (or deploy that airfoil) at the appropriate altitude/speed.

If this is the 'gist' of one or more of the ideas above, weigh this accordingly.

[djellison]

Design an aircraft that could take off from the Martian surface and accelerate to Mach 5 (to an appropriate altitude)

It would look like a rocket. To get to that sort of altitude and and speed with anything like a terran aircraft would require enormous aerodynamic surfaces given the low atmospheric pressure. It'd look like a U2 spy-plane on steroids and is an enormous ammount of mass, volume and engineering you do not need.

This really isn't a problem that requires dramatically outside the box thinking. 'chute and balute research is needed - particularly a large steering parafoil would be good. Then you simply scale an MSL like decent stage appropriately for terminal decent.

Doug

[tty]

It would look like a rocket. To get to that sort of altitude and and speed with anything like a terran aircraft would require enormous aerodynamic surfaces given the low atmospheric pressure. It'd look like a U2 spy-plane on steroids and is an enormous ammount of mass, volume and engineering you do not need.

No it wouldn't. U-2 with its large, very high aspect-ratio wings is built for subsonic flight, and technically it more or less reaches the end of the line for that flight regime. At 75,000 foot a U-2 only has 5-10 knots between low-speed stall and high-speed (compressibility) stall.

The average atmospheric pressure on Mars is equivalent to c. 100,000 feet on Earth so subsonic flight is probably out except possibly for extremely lightweight vehicles and structures (think Gossamer Albatross) which are far too fragile for re-entry. A aerodynamic entry vehicle for Mars would have to be optimized for supersonic to hypersonic flight and woulf probably be a waverider (B-70 on steroids).

I agree that outside the box thinking is needed here. Perhaps some kind of vehicle that can change its orientation and/or form drastically depending on the flight regime (like Spaceship One, only more so). Maybe some kind of "flying disc" that works as a flying wing at hypersonic speed and then rears up to 90-degree AoA somewhere around mach 5.

But you will still need rockets for the landing.

[djellison]

so subsonic flight is probably out except possibly for extremely lightweight vehicles and structures (think Gossamer Albatross)

http://marsairplane.larc.nasa.gov/index.html

Space Ship One on Mars? An expensive brick. Here's how an entry vehicle can change it's shape enormously....get loads of strong material, tie it to the vehicle with string, and throw it out the back. It might look a little something like this - http://marstech.jpl.nasa.gov/images/paraDev.jpg

There's out the box thinking, and there's sci-fi. Several suggestions in this thread have both feet well and truely in the second catagory, and this isn't the place for that sort of discussion. Chutes, Ballutes, Airbags...all good stuff. Flying saucers and SS1....not. Looks like no one has learnt the lesson of the space shuttle.

Doug