I'd like to repeat this: In its present state a Dragon capsule can deliver 1 mt of payload to the surface or Mars
Quote from: douglas100 on 04/18/2012 07:34 pmI don't think that planetary landers are general purpose. I think they are specialized vehicles and should be custom designed for the mission and the planetary environment they are going to land in.Planetary environment, yes, but mission - why?Wouldn't it make scientific community happy if there was a predictable schedule of small mars landers with fixed capacity every 2 years - say, two or four of them every time ? And the missions would be designed for the lander, not vice versa.
I don't think that planetary landers are general purpose. I think they are specialized vehicles and should be custom designed for the mission and the planetary environment they are going to land in.
Well, SpaceX is not the only one who says a Dragon could land on Mars. When the NASA engineers studied the proposal they didn't see any evident reason why a Dragon could not do it either.
What's the definition of a mars lander? Because from my point of view it is anything that can land on Mars without crashing, while carrying some significant payload.
As they say, the perfect is enemy of the good enough.
Quote from: charliem on 04/18/2012 11:58 pmI'd like to repeat this: In its present state a Dragon capsule can deliver 1 mt of payload to the surface or Mars [citation needed]
>Falcon Heavy can throw Dragon to Mars– Throw mass > 10 t to Mars (C3 ~ 10 km2/s2)– Red Dragon injected mass ~ 6.5 t plus payload>
As far as designing for the mission is concerned, consider the two missions: landing a small weather station and landing a human habitat on Mars. I think it's obvious that different designs of landers would be needed for those.
Remove the pressure vessel and Design a back shell
"Present state" is a bit of a stretch, as there's no pacific ocean on mars to splash down into. Assuming announced & funded developments go as planned, Dragon ought to be able to do so in the future.
Remove the pressure vessel and Design a back shell that is either jettisoned on descent or simply opened on the ground. We would then have a dragon 'truck' that could land more than one tonne on mars ( pressure vessel weight being replaced by payload mass).A landing system can be a common element but the bulk of the expense will then be the unique cargo landed.I'd prefer a five meter verion though as that would allow even greater mass to be landed.It could perhaps form the basis of a multi lander settlement project. One way? Just thoughts and only basic math in the above.
OK, so we take a Dragon capsule, make it a different size, and make it not a capsule any more.How is that different to making a 5m heatshield plus backshell plus retros? Which is the 'dedicated Mars lander' that I suggested could be made using SpaceX technology.
Quote from: douglas100 on 04/19/2012 07:57 amAs far as designing for the mission is concerned, consider the two missions: landing a small weather station and landing a human habitat on Mars. I think it's obvious that different designs of landers would be needed for those.Thats not obvious to me at all. I think it would be perfectly possible to design the entire mission architecture and hardware to be landed by the same lander.
Quote from: charliem on 04/18/2012 11:58 pmWell, SpaceX is not the only one who says a Dragon could land on Mars. When the NASA engineers studied the proposal they didn't see any evident reason why a Dragon could not do it either.If you read the first two pages of the Red Dragon thread you'll see this has already been discussed. Some engineers at Ames looked at it. It wasn't an official NASA study.
... I suggest there will be different designs of Mars landers to handle different classes of landed payloads. A general lander, Dragon derived or otherwise, cannot handle all the possibilities.
It's possible but it's not the best solution. A general purpose lander would have to be able to deliver payloads of greatly varying sizes and masses, depending on the mission.
As you said, today we have a whole family of general purpose launchers, and depending on the case they choose one or the other, but what no one does anymore is to design a new one for each mission.I think the time is coming to do it also with the [mars] landers.We already design the payloads having in mind the available launchers. Why not doing it with also thinking in the available landers (once there is one, evidently)?
And better ( best ) is the eternal vile enemy of good enough. Best solutions tend to be time consuming and expensive. Often more than several orders of magnitude more than a working solution.
There are a lot of variables. What size is it to be? What is the payload? Does it have to be removed from the capsule? If not, how is it to be powered? What landing site elevation do we aim for?If you propose a single design of Mars lander, bang goes all your flexibility.The current system is pretty good. NASA designed an entry and landing system back in the 70s at huge cost. They have managed to scale and modify this ever since to suit every payload them have wanted to land.Also, you should read 'Roving Mars' to see how JPL tried to shoehorn the MERs into a MPF-size lander. Sometimes these ideas just don't work out.
We don't have to design a new LV for every mission because there is a choice available.Are you suggesting we go down the same route for Mars payloads?
If you propose a single design of Mars lander, bang goes all your flexibility.
Also, you should read 'Roving Mars' to see how JPL tried to shoehorn the MERs into a MPF-size lander. Sometimes these ideas just don't work out.
I've read a discussion somewhere else about it and landing a big mass on Mars is not so simple. Because thin marsian atmosphere does not provide enough friction, there is a limit on mass of landing craft that can be slowed down to subsonic speed (in combination with parachutes), which is required for thrusters to work properly.
That's one on the beauties of Dragon (if works as planned), it won't need to slow down to subsonic speeds, nor use parachutes. It's, indeed, a quite different machine than its precursors.
Quote from: charliem on 04/20/2012 04:46 pmThat's one on the beauties of Dragon (if works as planned), it won't need to slow down to subsonic speeds, nor use parachutes. It's, indeed, a quite different machine than its precursors.Nope. The same rule applies. You are referring to Dragon landing on thruster, right? The problem with that is that if you try to land on thrusters with supersonic speeds they are difficult to control....