Author Topic: A Dragon derived general purpose Mars lander?  (Read 55586 times)

Offline charliem

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A Dragon derived general purpose Mars lander?
« on: 04/17/2012 07:46 pm »
Until now all the landers sent to Mars have been designed with only one very specific mission in mind. Few have been used more than once. That means the landing platform research, development and building costs kept high, impacting heavily on Mars mission budgets.

If we want to see human footprints on Mars one day, costs for every phase of the enterprise has to go down. Reductions in [earth] launch prices seem to be already under way. Achieving the same with [mars] landing would take us one more step towards that goal.

I think that a [first generation] general purpose, expendable, cheap mars lander, is doable in a relatively short time if developed from what already exists. It'd make Mars exploration much more affordable, and could also help to deliver hardware and/or consumables for the first human expeditions.

I was intrigued by what I read about a possible Red Mars mission once Falcon Heavy and the Dragon escape system become operational, although the declarations about it only be able to deliver 1 mt of payload sounded oddly small compared with its capabilities on Earth.

That took me to wonder if the Dragon could be used as base for a new vehicle that could fulfill the role I talked about before, with as little change as possible.

After some BOE found why the 1 mt figure: for the same ship dimensions (mass included) the terminal velocity on Mars is roughly five times that on Earth. Add that up with the low delta-v capability of the Dragon (only 1.290 kg of N2O4/MMH propellants) and that's it.

Well, 1 mt is not bad (1 mt is 10% more than the Curiosity rover), specially at the price, but there's also the small problem of how to extract the payload from the interior (and, of course, in this case the heavier the better).

So two questions: (1) Payload Extraction, and (2) Mass Enhancement, and the answers cannot be too radical, because if they imply a complete redesign then we'd loose right what we want to keep, low price and time.

The second problem looks the easier to solve: Interior supplementary tanks (if a F/A-18 can do it why not a spacecraft?). One from the aprox. 10 m3 of interior space of a Dragon gives you another tonne of propellants, elevating, if I'm not mistaken, the payload mass from 1 to 3 mt. Not bad. And with two tonnes of added propellants the payload mass gets near 5 mt.

About the first problem. Red Dragon solves it by simply not getting the payload out at all, drilling directly through the hull. Ingenious but not a general solution.

Someone suggested in other thread an extendable crane that could elevate the payload to let it out through the 1.3 m wide forward hatch, and also gently down outside.

Seems like a possibility, although it'd have the hatch size limitation (the Opportunity rover would not had fit, even folded, much less something bigger).

I wonder if there is a simple method for widening the aperture without having to completely re-engineer the hull. Sounds far fetched but if the payload is protected or though enough, what about a thermite cordon around the half level of the vessel and some hydraulic pushers? I know zit about explosives but I'd like someone with more knowledge on the matter confirm its impossibility.

And I know, Falcon Heavy doesn't exist yet, neither the Dragon escape system. I'm building on air, sure, but, hey, without a lot of previous dreams no rocket would had ever been built.
« Last Edit: 04/17/2012 09:57 pm by Chris Bergin »

Offline Kaputnik

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Re: A Dragon derived general purpose Mars lander?
« Reply #1 on: 04/18/2012 09:22 am »
There have been eight landing attempts over 36 years at Mars. Six different designs, or five if you count MPL/Phoenix as being more-or-less the same.

Over that sort of time technology moves on, and in each case payload requirements were quite different. E.g. do you want a rover, that can land on its wheels or egress a platform? Do you want a lander with legs to maximise surface payload? What size does this paylaod need to be?

There have been attempts to standardise Mars landers. In fact, they have all been born of the same development program already, leading to a standardised but scalable basic entry vehicle shape and parachute. That is already much more standardisation than you will find in most spacecraft designs given the spread of time and different purposes and payloads.

For MER, it was initially proposed to reuse the MPF lander design, but in the end they had to scale it all up to fit the payload.


Anyway, as to Dragon- I think some of the technologies behind it are sound, and applicable to a Mars lander. But it would be ridicuolous to handicap the design by basing it on the Dragon capsule itself. Firstly, why restrict the diameter to 3.6m? Why not take it out to the maximum that the LV can cope with? Landed mass scales closely with vehicle diameter. Secondly, why put everything inside a sealed capsule? The basic design should be more flexible than that, allowing a multitude of different payloads to be flown.

When it comes to a human mission to Mars, I do think a standardised lander design is the way to go. We will need to build up flight experience with it landing unmanned payloads before we entrust humans to the system. However, to able to do this, the design must have the flexibility to land *all* of the mission elements, be they habitats, rovers, ascent vehicles, or indeed the crew.
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Offline kevin-rf

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Re: A Dragon derived general purpose Mars lander?
« Reply #2 on: 04/18/2012 01:17 pm »
There have been eight landing attempts over 36 years at Mars. Six different designs, or five if you count MPL/Phoenix as being more-or-less the same.

Small nit, Eight US, actually by my fingers Seven with one more on the way. That number does not include Russian and European attempts.
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Offline Kaputnik

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Re: A Dragon derived general purpose Mars lander?
« Reply #3 on: 04/18/2012 02:06 pm »
Correct, I was counting MSL as being 'in progress'. Also I didn't want to complicate things by adding in the various Soviet and one ESA attempts, the context being standardising landers- doing this internationally would be even more difficult.
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Offline Sparky

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Re: A Dragon derived general purpose Mars lander?
« Reply #4 on: 04/18/2012 02:18 pm »
Just a thought:

In terms of extraction, Dragon (and likely any Mars derivative) has a CBM sized opening on top. Could some of the landing legs be designed to be extendable/retractable, to tip the capsule onto its side after landing?

Offline A_M_Swallow

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Re: A Dragon derived general purpose Mars lander?
« Reply #5 on: 04/18/2012 04:00 pm »
Just a thought:

In terms of extraction, Dragon (and likely any Mars derivative) has a CBM sized opening on top. Could some of the landing legs be designed to be extendable/retractable, to tip the capsule onto its side after landing?

The manned Dragon and Dragonlab have a side hatch.  It may be simpler for surface equipment to exit through that.
http://www.spacex.com/downloads/dragonlab-datasheet.pdf

Offline charliem

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Re: A Dragon derived general purpose Mars lander?
« Reply #6 on: 04/18/2012 05:02 pm »
There have been attempts to standardise Mars landers. In fact, they have all been born of the same development program already, leading to a standardised but scalable basic entry vehicle shape and parachute. That is already much more standardisation than you will find in most spacecraft designs given the spread of time and different purposes and payloads.

For MER, it was initially proposed to reuse the MPF lander design, but in the end they had to scale it all up to fit the payload.


Anyway, as to Dragon- I think some of the technologies behind it are sound, and applicable to a Mars lander. But it would be ridicuolous to handicap the design by basing it on the Dragon capsule itself. Firstly, why restrict the diameter to 3.6m? Why not take it out to the maximum that the LV can cope with? Landed mass scales closely with vehicle diameter. Secondly, why put everything inside a sealed capsule? The basic design should be more flexible than that, allowing a multitude of different payloads to be flown.

Well Kaputnik, all you said is reasonable, not much different from what I've been thinking for years, but lately, as I realized that at the present slowing down pace most likely we are not going to see a human foot set on Mars before 2040 (or even longer, if ever), much less have a settlement, I've started to look for different approaches.

The traditional way of doing space exploration has been, to date, by specific mission oriented designs, most of them one of a kind (and yes, I'm aware of the many similarities between Viking, Pathfinder, MPL, MER, Phoenix and MSL, and even russian's Mars and ESA's Beagle).

That way is, no doubt, the ideal one if your resources are large enough to sustain it. The problem, as I see it, is that it looks like the R&D, and building, and operating costs of those awesome machines, are growing at a much higher rate than our financial capacity (or will if you prefer) allows.

And then I heard about Red Dragon.

At first was quite surprised. Never thought that a vehicle like that (a capsule! O_O) could be re-purposed to land and do science on Mars, but then wondered: If it can do that, what other things could it do? And then, following the same train of thought: What are the minimum changes necessary to turn it into a more general platform/lander?

A fresh design for a general purpose lander would be much more elegant, no doubt, but who is going to do it? And who is going to finance it? And how much time is going to take? After all, "they" had at least since 1975, 37 years, and I see no indication of any will to build anything remotely similar.

At least Dragon has one clear quality, it's [almost] already here.

So the question in my mind right now is: Do we keep waiting for the best, or do we try to go ahead with what we have, plus all the ingenuity we can muster?

And who said to restrict ourselves to 3.6 m? That's just a starting point. The fairing for a Falcon Heavy is 5.2 m in diameter. I see no reason to, at the very least, try to use that. But that is phase 2. Start humble, prove yourself, and then, maybe, you'll get farther.

P.E. I'm not advocating the use of Dragon for humans, but just as a starting point to speed up the previous steps.

Offline charliem

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Re: A Dragon derived general purpose Mars lander?
« Reply #7 on: 04/18/2012 05:08 pm »
The manned Dragon and Dragonlab have a side hatch.  It may be simpler for surface equipment to exit through that.
http://www.spacex.com/downloads/dragonlab-datasheet.pdf

Problem is size. The top hatch is more or less squared, and 1.3 m wide. The side hatch is much smaller (aprox. 0,66 x 0.7 m).

Online docmordrid

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Re: A Dragon derived general purpose Mars lander?
« Reply #8 on: 04/18/2012 06:59 pm »
Does "detived" in include he possibility of modifying the side hatch to be much larger, or perhaps to also include a folding/extensible ramp? I'd think that would be a good derivation jumping off point. Might also want to reduce the height to lower the c/g. The pressure vessel is made up of welded panels so ISTM mods like this would be a CNC w/plasma cutter away for a decent fabricator
« Last Edit: 04/18/2012 07:00 pm by docmordrid »
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Offline Kaputnik

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Re: A Dragon derived general purpose Mars lander?
« Reply #9 on: 04/18/2012 07:00 pm »
A fresh design for a general purpose lander would be much more elegant, no doubt, but who is going to do it? And who is going to finance it? And how much time is going to take? After all, "they" had at least since 1975, 37 years, and I see no indication of any will to build anything remotely similar.

Why not get SpaceX to do it? They are not averse to altering their designs. Of their seven launches, how many have been the exact same configuration?
The benefits of creating a dedicated lander rather than a modified LEO taxi would be huge, and the increased payload would probably pay for itself fairly quickly in terms of $/kg landed.

Quote
And who said to restrict ourselves to 3.6 m? That's just a starting point. The fairing for a Falcon Heavy is 5.2 m in diameter. I see no reason to, at the very least, try to use that. But that is phase 2. Start humble, prove yourself, and then, maybe, you'll get farther.
Well, I was sort of assuming you said it. If it's not 3.6m, it's not a Dragon.
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Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #10 on: 04/18/2012 07:34 pm »
 I think the basic premise is wrong.

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.

So first we should decide what the mission is. Is it a manned lander? Is it for cargo? Is it for science? I believe it will be far better and cheaper in the long run to start with a blank sheet of paper and design the vehicle for its particular purpose. Rather than taking something like Dragon and go through all sorts of permutations to modify it for another purpose we should start from the bottom up.

Now if SpaceX wish to design a Mars lander for a specific purpose, there is no reason why they cannot use Dragon technology and systems for it. But that is very different from starting with an already mature design and trying to morph it into something else.

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Offline starsilk

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Re: A Dragon derived general purpose Mars lander?
« Reply #11 on: 04/18/2012 07:35 pm »
Does "detived" in include he possibility of modifying the side hatch to be much larger, or perhaps to also include a folding/extensible ramp? I'd think that would be a good derivation jumping off point. Might also want to reduce the height to lower the c/g. The pressure vessel is made up of welded panels so ISTM mods like this would be a CNC w/plasma cutter away for a decent fabricator

depending on how the panels are arranged, you could presumably just hinge and open the whole top two thirds like flower petals... would be difficult to keep that as a 'pressure vessel' though.

Offline oiorionsbelt

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Re: A Dragon derived general purpose Mars lander?
« Reply #12 on: 04/18/2012 07:39 pm »
I think the basic premise is wrong.
 I believe it will be far better and cheaper in the long run to start with a blank sheet of paper and design the vehicle for its particular purpose.

SpaceX's Red Dragon proposal would sugest they disagree with you.
« Last Edit: 04/18/2012 07:39 pm by oiorionsbelt »

Offline starsilk

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Re: A Dragon derived general purpose Mars lander?
« Reply #13 on: 04/18/2012 07:45 pm »
I think the basic premise is wrong.

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.

So first we should decide what the mission is. Is it a manned lander? Is it for cargo? Is it for science? I believe it will be far better and cheaper in the long run to start with a blank sheet of paper and design the vehicle for its particular purpose. Rather than taking something like Dragon and go through all sorts of permutations to modify it for another purpose we should start from the bottom up.

Now if SpaceX wish to design a Mars lander for a specific purpose, there is no reason why they cannot use Dragon technology and systems for it. But that is very different from starting with an already mature design and trying to morph it into something else.

well, SpaceX are quite clear that they want to put people on Mars. so there is a pretty reasonable chance that some thought has been applied to using Dragon for that purpose - they've already repeatedly said the heat shield was designed to be capable of Earth reentry from Mars, for example.

I'm sure they'd very much like to have NASA sponsor testing that out by using it for unmanned landing(s). if Dragon can be hacked to land robots on Mars, then why design a whole new cargo lander? now you have to test BOTH of them. they've also made a conscious decision to use a "manned" (capable) vehicle for cargo transport to the ISS (cf Orbital's solution). I see a pattern here.

that's not to say a cargo lander wouldn't be necessary for Mars colonization.. but why not test out the vehicle you already have, first, before designing the next one?

Offline DaveH62

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Re: A Dragon derived general purpose Mars lander?
« Reply #14 on: 04/18/2012 07:59 pm »
Combining a few ideas into some questions.

Could they build a 5 meter dragon for Mars to increase payload? It would be a redesign, but could they keep the existing basic design and just expand the size?

Could the attach an upper stage rocket, where the trunk goes, to enter from orbit, and then fire Draco's once in the atmosphere? Seems like a safer method, and would increase payload capacity.

Could they increase the side hatch size and make it a ramp for offloading payload?

Do they have a articulating payload arm for moving payload that is won't roll out the ramp?

Lastly a comment: I do think standardizing delivery systems might constrain some payloads, but the payoff would be reduced development cycles, lower costs and reduced risks for each program. Maybe that is wrong, but it seems very reasonable to assume standardizing components and processes would reduce costs for space exploration as it has for all other industry.

Offline SpacexULA

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Re: A Dragon derived general purpose Mars lander?
« Reply #15 on: 04/18/2012 08:27 pm »
Why not get SpaceX to do it? They are not averse to altering their designs. Of their seven launches, how many have been the exact same configuration?
The benefits of creating a dedicated lander rather than a modified LEO taxi would be huge, and the increased payload would probably pay for itself fairly quickly in terms of $/kg landed.

Agreed, the cost per kg to Mars no matter what is going to way out pace any savings using refurbished/re purposed hardware.

Imagine how much payload SpaceX might be able to land with a PICAX heat shield scaled up to 4.5 Meters (Scaled up to fill their fairing), Draco thrusters hinged to allow for no cosine losses, and an airframe optimized for Mars entry. 

SpaceX has always said the long term goal is Mars, I can see 1-2 one off reuse of Dragon Capsules for Mars Landing, but if they ever get contracts to seriously go to Mars, it's really likely going to be a bird designed just for Mars Entry...

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Offline Bob Shaw

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Re: A Dragon derived general purpose Mars lander?
« Reply #16 on: 04/18/2012 09:14 pm »
Perhaps Red Dragon could deliver an anthropomorphic robot to Mars, and serve as a fuel store or battery pack. Just put a couch in, and some Apollo-style EVA handles on the exterior. My back of the envelope calculation suggests this would work on Luna, too...

Offline douglas100

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Re: A Dragon derived general purpose Mars lander?
« Reply #17 on: 04/18/2012 09:57 pm »

well, SpaceX are quite clear that they want to put people on Mars. so there is a pretty reasonable chance that some thought has been applied to using Dragon for that purpose - they've already repeatedly said the heat shield was designed to be capable of Earth reentry from Mars, for example.

That's exactly the point: Dragon designed as an Earth lander, not a Mars lander. It's quite feasible to imagine it being used to bring members of a Mars expedition back to Earth on the last stage of their journey. But it isn't a Mars lander (despite what Musk says).

From Kaputnik
Quote
Imagine how much payload SpaceX might be able to land with a PICAX heat shield scaled up to 4.5 Meters (Scaled up to fill their fairing), Draco thrusters hinged to allow for no cosine losses, and an airframe optimized for Mars entry.

Just what I was arguing: a Mars lander designed from the ground up, but using Dragon technology, makes much more sense. I believe it could actually be cheaper than "hacking" the current vehicle's configuration.
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Offline charliem

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Re: A Dragon derived general purpose Mars lander?
« Reply #18 on: 04/18/2012 11:58 pm »
That's exactly the point: Dragon designed as an Earth lander, not a Mars lander. It's quite feasible to imagine it being used to bring members of a Mars expedition back to Earth on the last stage of their journey. But it isn't a Mars lander (despite what Musk says).

Just what I was arguing: a Mars lander designed from the ground up, but using Dragon technology, makes much more sense. I believe it could actually be cheaper than "hacking" the current vehicle's configuration.

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.

Dragon is not the most beautiful solution but, what's the problem if it gets the job done?

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

I'd very much like to see SpaceX designing a mars lander from the ground up, and am convinced their engineers'd like it as much as we, probably even Elon would, but SpaceX is not a non-profit, and this work can be as expensive, if not more, that designing the Falcon 9, which took about $300 million to develop IIRC.

So the question is not if there are better solutions, because of course there are, the only question is whether there is one that we can afford, at least for now (are you not a bit tired of waiting, cause I 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 (each MER rover weighted 185 kg, and the MSL rover 925). If my BOE calcs are not wrong just adding 1 mt of propellant would add 2 mt to the payload capacity (leaving ~9m3 of free volume), and without having to touch the heat shield.

Offline savuporo

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Re: A Dragon derived general purpose Mars lander?
« Reply #19 on: 04/19/2012 12:09 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.
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