[X] My Assistant

[Guest_Zvezdichko_*]

Well, that's a tough question. What will happen, for example if Mars Phoenix fails to touch down successfully? Maybe I look a bit pessimistic, but I like to think in perspective. I think that:

1.If MSL managers give up the skycrane and decide to use Phoenix-like pinpoint landing system, it will effectively move the launch date from 2009 to 2011. Since there's no NASA orbiter planned for launch in 2009, maybe we won't have a new spacecraft then.

2. It will end the scout program or... the next scout mission will be a simple orbiter.

3. There will be several small landers in future, using the good old airbag bouncing method.

[djellison]

MSL is a retrorocket landing.

Doug

[Guest_Zvezdichko_*]

MSL is a retrorocket landing.

Doug

Well, I know, but I meant the old Viking way. I still don't see how they are going to keep a descent vehicle over the surface for a long time while the rover is being laid. Indeed, Spirit used such a technique during EDL, but for a short time.

They are three for three which is a far better success ratio than straight retros. Other methods have certainly worked, but given something as uncertain as putting cargo down softly on Mars, when you have an engineering model that clearly works and has been studied to death, it's reasonable to wonder why the powers that be would want to try something that has not been proven to the same degree.

Errr... Beagle 2 also used an airbag system ( though the official version suggests a parachute failure rather than an airbag failure ).
The Beagle case... The lack of any retro rockets should mean a bigger chance of failure ... if all other systems work.

[djellison]

I still don't see how they are going to keep a descent vehicle over the surface for a long time while the rover is being laid.

It's really not that hard a problem....take the Viking landing - and simply take the terminal decent speed and change it to zero. We're talking more than 30 years later. Phoenix could, technically, enter a hover a few metres above the surface ( not that there would be any point ). MSL is a big challenge, no doubt, but no more so than the orig. challenge of the Pathfinder landing.

The MER engineers are on record - to do airbags bigger than MER just doesn't add up. The ammount of mass you have to dedicate to the landing system is utterly enormous with airbags. To scale from a 180kg rover to a 700kg rover - the airbags and the structure to encase the lander would be many tonnes. Then - if they work with that much weight, you've got yards and yards of airbag material to try and get over to egress onto the surface. Airbags at that scale just don't make sense - period.

http://www.youtube.com/watch?v=q1UKwFfXmUY

Rob explains it best

Doug