Author Topic: A Dragon derived general purpose Mars lander?  (Read 55476 times)

Offline StephenB

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Re: A Dragon derived general purpose Mars lander?
« Reply #40 on: 04/20/2012 09:21 pm »
Would a dragon still be supersonic on Mars if they follow the entry profile where they gain altitude before starting to drop again?

Online Robotbeat

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Re: A Dragon derived general purpose Mars lander?
« Reply #41 on: 04/20/2012 10:11 pm »
Would a dragon still be supersonic on Mars if they follow the entry profile where they gain altitude before starting to drop again?
Yes. Terminal velocity at Mars is very high for that size/mass of an object because of the very thin atmosphere.

BESIDES, SUPERSONIC IS OKAY!!!

It's a performance penalty is all.
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Offline ChefPat

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Re: A Dragon derived general purpose Mars lander?
« Reply #42 on: 04/20/2012 10:31 pm »
From the "Red Dragon" thread.
What speed will Dragon be going at the top of the "rise"?
Playing Politics with Commercial Crew is Un-American!!!

Offline charliem

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Re: A Dragon derived general purpose Mars lander?
« Reply #43 on: 04/20/2012 11:54 pm »
From the "Red Dragon" thread.
What speed will Dragon be going at the top of the "rise"?

Not enough data but if that graphic is more or less accurate you could calculate a very rough first approximation by measuring the altitude and range from the top point to landing.

About the terminal velocity don't have that data either, but can always try to estimate from what little we know. Mine is 380-450 m/s.

Offline luksol

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Re: A Dragon derived general purpose Mars lander?
« Reply #44 on: 04/21/2012 07:12 am »

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.


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.
Oh, don't get me wrong, I'd be delighted if supersonic wasn't a problem. I was just referring to something I've read, I am not an expert, just enthusiast. One question though. Has this been tried ? I mean landing on thrusters while supersonic?

Offline Nathan

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Re: A Dragon derived general purpose Mars lander?
« Reply #45 on: 04/21/2012 08:05 am »
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.
I wasn't disagreeing with you I just prefer the sound of my own voice! A dedicated large dragon with backshell and retros sounds fine to me. I think the existing dragon could be modified to have a backshell (strong enough for entry) to increase payload to surface in the near term before the dedicated large lander is built though.
Given finite cash, if we want to go to Mars then we should go to Mars.

Offline go4mars

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Re: A Dragon derived general purpose Mars lander?
« Reply #46 on: 04/22/2012 04:18 pm »
Good eye.  I added a few in bold.  No one will be bored.
Propulsion team:
Kestrel
Merlin 1A
Merlin 1B
Merclin 1C
Draco
Merlin Vac
Merlin 1D
Super Draco
Highly reusable version of 1D
Methane version of 1D
Staged combustion version of 1D-sized
Raptor cryogenic stage
Merlin 2
Subsequent merlin 2 upgrades
Niche engines for parts of the reusable Mars architecture


or

Superstructures:
Falcon 1
Falcon 9
Falcon 9 Mk2
Falcon 9 Heavy
reusability upgrades
raptor stage
methane versions
15 meter diameter per core BFR
reusable ISRU mars architecture components
22 meter diameter BFR cryogenic upper stage


IMHO will see a dedicated Mars or Moon Lander then (2015-2017), but no sooner.
I think dragon would more likely continue to be essentially an all-purpose vehicle in that timeframe but with those added capabilities.


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.  He might very well have said, "we will design a capsule which to the best of our early knowledge is step-wise evolvable for landing both on Earth and on Mars with pre-determined upgrades using certain general assumptions".   That would have been after Gary's capsule work, so I don't know if anyone here could confirm or deny this. 
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Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #47 on: 04/22/2012 10:20 pm »

I suspect Elon has a bit more insight into his design requirements than you do. 

And I suspect that you are too eager to accepting Musk's predictions at face value. Around 2006 or so he predicted (I paraphrase) "when the Space Shuttle retires in 2010, there will be only one partially reuseable launch vehicle in the world--Falcon 1."

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.
Douglas Clark

Offline oiorionsbelt

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Re: A Dragon derived general purpose Mars lander?
« Reply #48 on: 04/22/2012 10:24 pm »

I 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.
If not 'the best', do you think it is a 'likely' Mars Lander?

Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #49 on: 04/22/2012 10:39 pm »
At the moment, no. Now of course, that can change. But currently there are no Mars landers planned by NASA after MSL and ExoMars is in flux. The budget climate is poor.

Now 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.
Douglas Clark

Offline oiorionsbelt

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Re: A Dragon derived general purpose Mars lander?
« Reply #50 on: 04/22/2012 10:47 pm »
Do you think Red Dragon is an after thought, or do you think Mars was contemplated earlier on in the design?

Offline charliem

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Re: A Dragon derived general purpose Mars lander?
« Reply #51 on: 04/23/2012 03:47 am »
... 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.

Now, I'd like to see that  ;D

Could SpaceX develop and build it for a fraction of the cost we are used to, as they did with Falcon 9?

Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #52 on: 04/23/2012 08:57 am »
Could 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.

SpaceX has no experience of landing on Mars, experience which JPL and its contractors have gained only at great expense over many years. Of course SpaceX can learn from and build on that experience. Maybe they could do a lander "a bit" cheaper, but not much. 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.
« Last Edit: 04/23/2012 09:00 am by douglas100 »
Douglas Clark

Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #53 on: 04/23/2012 09:07 am »
Do you think Red Dragon is an after thought, or do you think Mars was contemplated earlier on in the design?

I don't know. I think Musk is sincere in his Mars ambitions, but I have no idea if Red Dragon was an afterthought.
Douglas Clark

Offline charliem

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Re: A Dragon derived general purpose Mars lander?
« Reply #54 on: 04/23/2012 06:22 pm »
Could 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.

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 :P).

Offline go4mars

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Re: A Dragon derived general purpose Mars lander?
« Reply #55 on: 04/23/2012 07:00 pm »
Mars landers are like launch vehicles, you only have one chance to get it right. So you have to test meticulously, which is expensive.
They tested the merlin vacuum by sticking it on a rocket.  Using your examples (Beagle 2 or MPL), if they made a few of them at the same time instead of just 1, then subsequently launched versions would have been better and cheaper.  It isn't like SpaceX plan to only ever land 1 thing on Mars.  Doing the mission faster better and cheaper could be a good way of gathering data for  follow-on red dragons (improving the success). 

If you go for cheaper (remember "faster, better, cheaper?") then you risk being Beagle 2 or MPL.
Conversely, if you don't aim to be faster & better & cheaper, you likely won't be. 
« Last Edit: 04/23/2012 07:04 pm by go4mars »
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Offline StephenB

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Re: A Dragon derived general purpose Mars lander?
« Reply #56 on: 04/23/2012 07:27 pm »
From 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?
« Last Edit: 04/23/2012 07:49 pm by StephenB »

Offline go4mars

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Re: A Dragon derived general purpose Mars lander?
« Reply #57 on: 04/23/2012 07:50 pm »
From 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?
Correct.  But I think it's reasonable to assume he means tangential velocity.
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Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #58 on: 04/23/2012 08:31 pm »

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 :P).

I assumed you asked me for my opinion and that's what I gave you. If I gave you the impression I was "so sure" of the opposite, I apologize. I certainly hold the opinion quite strongly, but it is just that, an opinion.

Now I think you are on the right lines with the development cost of Falcon 9, but you  said develop and build it for a fraction of what we are used to. I mistook that for the cost of a Falcon 9 flight to a customer.

But I think that comparing the development of a launch vehicle with the development of a spacecraft might not be too useful. Spacecraft (I mean main payloads) are often more expensive than their launch vehicles. Look at the delay in launching the COTS Demo C2+: the delay is in the spacecraft not the F9. I suggest that major spacecraft are harder to do than launch vehicles and that a Mars lander is harder (and more expensive) to do than a cargo vehicle to ISS. Remember there have been over 100 successful automatic cargo flights to space stations , but only 6 successful Mars landings.

I think it makes more sense to compare like with like. We should compare a hypothetical SpaceX Mars lander with real Mars landers past and present when we debate whether SpaceX can do a Mars lander radically cheaper.

And in return, my question to you is, do you think they can do a Mars lander a lot cheaper than in the past and if so, why?
Douglas Clark

Offline oiorionsbelt

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Re: A Dragon derived general purpose Mars lander?
« Reply #59 on: 04/23/2012 08:51 pm »
 I think they will, because like you, I believe Elon is sincere in his Mars ambitions.
If he can't do it a lot cheaper those ambitions won't amount to much.
So it seems that for the first time there is someone with the 'possible' means and the sincere desire too get to Mars, IF they can to it cheaply enough.

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