Would a dragon still be supersonic on Mars if they follow the entry profile where they gain altitude before starting to drop again?
From the "Red Dragon" thread.What speed will Dragon be going at the top of the "rise"?
Quote from: luksol on 04/20/2012 08:18 pmQuote 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....Not true. Gosh darnit, why does EVERYONE on the internet think this? It's been refuted several times. Off-axis thrusters are not so difficult to control.
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....
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: Nathan on 04/19/2012 01:22 pmRemove 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.
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.
Propulsion team:KestrelMerlin 1AMerlin 1BMerclin 1CDracoMerlin VacMerlin 1DSuper Draco Highly reusable version of 1DMethane version of 1DStaged combustion version of 1D-sizedRaptor cryogenic stageMerlin 2Subsequent merlin 2 upgradesNiche engines for parts of the reusable Mars architectureorSuperstructures:Falcon 1Falcon 9Falcon 9 Mk2Falcon 9 Heavyreusability upgradesraptor stagemethane versions15 meter diameter per core BFRreusable ISRU mars architecture components22 meter diameter BFR cryogenic upper stage
IMHO will see a dedicated Mars or Moon Lander then (2015-2017), but no sooner.
That's exactly the point: Dragon designed as an Earth lander, not a Mars lander...it isn't a Mars lander (despite what Musk says).
I suspect Elon has a bit more insight into his design requirements than you do.
Quote from: go4mars on 04/22/2012 04:18 pmI suspect Elon has a bit more insight into his design requirements than you do. He is not always right, and it is not a given that using the current Dragon design is the best way to do a Mars lander.
... imagine a bunch of billionaires come along and say "Elon, will you do a Mars landing for us?" (I don't think SpaceX could fund it themselves). Then I think the better (and cheaper) way to do it would be to design the spacecraft from the ground up, using Dragon derived technology to achieve the mission goal.
Could SpaceX develop and build it for a fraction of the cost we are used to, as they did with Falcon 9?
Do you think Red Dragon is an after thought, or do you think Mars was contemplated earlier on in the design?
Quote from: charliem on 04/23/2012 03:47 amCould SpaceX develop and build it for a fraction of the cost we are used to, as they did with Falcon 9?What do you mean by a "fraction?" 10%? 50%/ 98%? I assume you mean "a lot" cheaper. It appears that Falcon 9 is "a bit" cheaper than other launch vehicles, but not "a fraction" of their cost. There has been considerable skepticism of SpaceX's prices on other threads.So, to answer your question on that basis: no.
Mars landers are like launch vehicles, you only have one chance to get it right. So you have to test meticulously, which is expensive.
If you go for cheaper (remember "faster, better, cheaper?") then you risk being Beagle 2 or MPL.
Quote from: ChefPat on 04/20/2012 10:31 pmFrom the "Red Dragon" thread.What speed will Dragon be going at the top of the "rise"?Surely the vertical component of the speed velocity is zero at that point?
By a fraction I mean half or less.I'm by no means certain, just wondering, but fail to see how you can be so sure of the opposite.Comparing price tags is difficult when most are hidden. What we do know is SpaceX has repeatedly declared Falcon 9 and Dragon development costs were about $300 million each (of course they could be lying ).