Author Topic: A Dragon derived general purpose Mars lander?  (Read 55519 times)

Offline Kaputnik

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Re: A Dragon derived general purpose Mars lander?
« Reply #20 on: 04/19/2012 07:23 am »
I'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]
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Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #21 on: 04/19/2012 07:57 am »
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.
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'm sure it would make them very happy. But the basis of small landers already exists: the MER/Phoenix system with either airbags or thrusters for the final touchdown. Dragon, as designed, is not required for that.

What's missing is not the technical means but the budget.

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.

The claim has been that a Dragon derived vehicle would be cheaper. I am doubtful of this. SpaceX have a long way to go before they will have an operational Mars EDL system. That experience will cost. And they have enough on their plate at the present time, anyway.
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Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #22 on: 04/19/2012 08:16 am »

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.

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.

Quote
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.

Agreed.

Quote
As they say, the perfect is enemy of the good enough.

I agree with that too. I'm not claiming that Dragon won't work or that the other approach is "perfect." I'm claiming that Dragon will not necessarily be cheaper and that the other approach is better.
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Offline docmordrid

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Re: A Dragon derived general purpose Mars lander?
« Reply #23 on: 04/19/2012 09:05 am »
I'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]

This do?

Quote
>
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
>
DM

Offline dcporter

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Re: A Dragon derived general purpose Mars lander?
« Reply #24 on: 04/19/2012 11:58 am »
"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.

Offline savuporo

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Re: A Dragon derived general purpose Mars lander?
« Reply #25 on: 04/19/2012 12:47 pm »
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.
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.
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Offline Nathan

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Re: A Dragon derived general purpose Mars lander?
« Reply #26 on: 04/19/2012 01:22 pm »
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.
Given finite cash, if we want to go to Mars then we should go to Mars.

Offline ChefPat

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Re: A Dragon derived general purpose Mars lander?
« Reply #27 on: 04/19/2012 02:14 pm »
Remove the pressure vessel and Design a back shell
I believe the pressure vessel is also the "frame" that everything attaches to.
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Offline Kaputnik

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Re: A Dragon derived general purpose Mars lander?
« Reply #28 on: 04/19/2012 02:38 pm »
"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.

'Present state' is indeed a stretch.

At the moment, Dragon has proved that it can do a couple of orbits in LEO and then make a splashdown on Earth.

The super-dracos need to be finished, operational, and then qualified for Mars operation.
Some sort of landing gear needs to be designed and operational.
The Dragon would need significant mods to take account of the different aspects of the mission:
- longer total duration
- very different communications requirements
- very different thermal environment
- surface operations are again different, only moreso

How the vehicle operates on the surface is a huge question as well. Any sort of solar array deployment is going to need a Heath-Robinson deployment mechanism. Internal power supplies are more likely, but again would need to be qualified and tested. Thermal management on the surface is again something to tackle.
To some extent the surface operation mods depend on the vehicle's configuration and payload once operational on the surface. This is likely different for different types of mission... leading us back to bespoke landers.

Also it should be no small issue that the proposed descent/landing profile for a Red Dragon is very different from anything that has been attempted before. It is a much bigger difference than, e.g, Viking to MSL, or Viking to MER.
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Offline Kaputnik

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Re: A Dragon derived general purpose Mars lander?
« Reply #29 on: 04/19/2012 02:39 pm »
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.
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Offline SpacexULA

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Re: A Dragon derived general purpose Mars lander?
« Reply #30 on: 04/19/2012 03:42 pm »
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.

From what I have read SpaceX likes to keep their design teams busy with 1 project at a time, example:

Propulsion team:
Kestrel
Merlin 1A
Merlin 1B
Merclin 1C
Draco
Merlin Vac
Merlin 1D
Super Draco

or

Superstructures:
Falcon 1
Falcon 9
Falcon 9 Mk2
Falcon 9 Heavy

These items got developed pretty much 1 at a time, and dimes to donuts it was ruffly the same crew that did all of their designs.

At some point around 2015-2017 (hopefully) SpaceX is going to finalize the LEO, propulsive landing Dragon, and very likely about that time SpaceX will move the team working on Dragon to their next project.  IMHO will see a dedicated Mars or Moon Lander then, but no sooner.


« Last Edit: 04/19/2012 03:43 pm by SpacexULA »
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Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #31 on: 04/19/2012 07:19 pm »
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.
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.

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.

It would be a bit like having a general purpose launch vehicle. Imagine that it was Delta IVH. You could use this vehicle to launch anything up to 20 tons into LEO. That covers a large range of possible payloads. But imagine using it to launch only a small science satellite. You could do it, but it makes no sense. So instead we have different classes of vehicles to handle different classes of payloads.

In a similar way, 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.
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Offline charliem

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Re: A Dragon derived general purpose Mars lander?
« Reply #32 on: 04/20/2012 01:24 am »
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.
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.

Maybe it was not an official study, but I think it was more than the result of a superficial look by "some engineers" (thanks docmordrid):

ARC (Ames): John Karcz, Gary Allen, Alfonso Davila, Brian Glass, Jennifer Heldmann, Lawrence Lemke, Margarita Marinova, Christopher McKay, Carol Stoker, and Kerry Trumble
KSC (Kennedy): Phil Metzger and Tony Muscatello
LRC (Langley): Artem Dyakonov and Karl Edquist
JSC (Johnson): Jerry Sanders

... 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.

I never suggested that this had to be the ONLY general purpose mars lander, only thing I said is that Dragon could serve as base for the first one.

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 about what's cheaper, if adapting Dragon or building something new based on its tech. I have no doubt that in the long run a new platform can be cheaper, but there is no long run unless there is a short run first, we have to start somewhere.

"Aim to the stars and if you don't reach them maybe you'll reach the Moon" is not always good advice, some times you just end up with spit on your face.

Offline savuporo

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Re: A Dragon derived general purpose Mars lander?
« Reply #33 on: 04/20/2012 05:14 am »
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. 
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.
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Offline Kaputnik

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Re: A Dragon derived general purpose Mars lander?
« Reply #34 on: 04/20/2012 07:30 am »
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)?

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?

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.
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Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #35 on: 04/20/2012 09:48 am »

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.

I've never heard the best called "vile" before.

Your point is correct when applied to simple technology. But we are talking about advanced technology where "good enough" has to be very good indeed. That's why I view the claim that designs using adapted from Dragon technology will be cheaper with considerable skepticism. There is no prospect of building a Mars lander that is "several orders of magnitude" cheaper at the present time. A "cheap" lander was tried--Beagle 2--and it failed. The team were underfunded and didn't do all the testing that was necessary.

From Kaputnik:

Quote
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.

+1
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Offline luksol

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Re: A Dragon derived general purpose Mars lander?
« Reply #36 on: 04/20/2012 10:16 am »
I just want to point out that increasing payload mass is not so desirable as it sounds.

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.

I am not an expert, so I have no idea about exact numbers, but if requested I can dig out an article where I've read about it.

Apparently MSL is just below this limit, so I wouldn't be too existed about Dragon delivering even more mass, not now at least.
There are some ways to overcome this problem that are being studied at the moment, but my knowledge about that is almost non-existant so I will not say anything not to confuse anyone. Maybe engineers will solve this problem in near future.

Sorry for being a bit vague, like I said before, no expert! :)
« Last Edit: 04/20/2012 10:17 am by luksol »

Offline charliem

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Re: A Dragon derived general purpose Mars lander?
« Reply #37 on: 04/20/2012 04:46 pm »
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?

Yep, that's exactly what I'm suggesting, for the long run but starting now.

Settlement or not, humans or just hardware, how many more $2.5 billion missions like MSL do you thing NASA'll be able to finance, even in international partnerships? (the lander is only a portion, but not negligible)

If you propose a single design of Mars lander, bang goes all your flexibility.

Let me quote myself: "I never suggested that this had to be the ONLY general purpose mars lander, only thing I said is that Dragon could serve as base for the first one."

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.

And sometimes they do. I think there's some indication that this could be one of those. The preliminary cost estimation for Red Dragon LV and lander sounds almost ridiculous, less that $200 million.

For God's sake, NASA even tried to develop new electrical engines for Curiosity, and had to abandon the idea because the mounting costs. How many times are they going to try reinvent the wheel? (not that I'm against reinventing a better wheel, but not if that means going broke).

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.

Offline luksol

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Re: A Dragon derived general purpose Mars lander?
« Reply #38 on: 04/20/2012 08:18 pm »

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. So difficult that apparently noone wants to try. You need to slow down first. Then fire thrusters.

Offline Robotbeat

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Re: A Dragon derived general purpose Mars lander?
« Reply #39 on: 04/20/2012 08:29 pm »

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. A big thruster right in the middle of the heatshield would lower the drag, but even that is possible. Dragon's (currently abort) thrusters are mounted around the perimeter, so they don't have to reduce drag.

Red Dragon has technical difficulties. But this oft-repeated supersonic retropropulsion thing isn't the kind of show-stopper everyone on the Internet thinks, not even close.

Current Mars lander designs slow to subsonic speeds because that's generally a lot more mass-efficient than propulsive landing, and current payloads have generally been small enough that supersonic retropropulsion isn't needed.
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