Mars Direct 2007

Marsman · 2007-03-17 04:52:47

I have some questions I was hoping to get your comments on and any MS members please chime in if you know anything. Where does the Mars Society stand with Mars Direct these days? Where does Zubrin stand with his plans from over 10 years ago? In light of all of the research in the last 10 years and lessons we are learning from the various robotic missions there has MS changed mission plans or Zubrin? If so what are those new plans, and if not, how does Mars Direct deal with all the criticism and new information over the last few years?

Mars_B4_Moon · 2007-03-19 03:08:59

politically Mars direct could be soon dead, now that NASA has given priority to re-enact July 20 with their 'Apollo on steroids' program.

cIclops · 2007-03-19 03:45:28

politically Mars direct could be soon dead, now that NASA has given priority to re-enact July 20 with their 'Apollo on steroids' program.

When was Mars Direct ever politically alive?

GCNRevenger · 2007-03-19 06:57:12

DRM was never really an official, serious plan, more of just a design study.

Martian Republic · 2007-03-19 09:25:53

Without putting words into Roberts Zubrin mouth or adding my own opinion to it. The Mars Direct was always Roberts Zubrin plan and as far as I can tell, still is his plan. As to whether he has changed his plan any or has modified his plan, I don't know.

As far as everybody else on Mars Society, they have there own opinions as to what needs to happen and they very all over the place as to what we should and should not be doing or whether they even support Roberts Zubrin Mars Direct Plan at all.

As far as the criticism of the Mars Direct Plan, I don't know if it been addressed and you will get different responses to that too.

About the only thing you you can say about Mars Society as a group is that we all believe that we should be going to Mars, but we have idea's of how we should get there and on how we should accomplish this goal.

Larry,

cIclops · 2007-03-19 09:31:23

NASA have a plan and they have started building the hardware. They are working right now on an updated Mars architecture based on DRM 3.0 which in turn is based on Zubrin's Mars Direct. It's the only game in town, we should all get behind it.

RobS · 2007-03-19 12:34:38

If you compare the designs for the Hab in Zubrin's Mars Direct book to designs used in the Arctic and designs mentioned in various places, it appears they have considered modifications to the interior layout. But there is no reason for them to update Mars Direct every two or three years, it seems to me. People will start worrying about details instead of the overall package. As GCNRevenger will note, there are enough problems with the overall plan. Updating the design and mass allocations may actually raise more doubts than generate assurances. The time and place to update Mars Direct would be by NASA if they adopted the plan. And in a sense that is what NASA has done; the DRM is their modification of Mars Direct.

-- RobS

cIclops · 2007-03-19 12:54:25

It makes perfect sense for NASA to update DRM 3.0 now that ESAS has been finished and the Constellation system begun. BTW DRM Version 3.0 was published in June, 1998 and ESAS was completed in July 2005.

Lobster · 2012-01-04 13:25:01

You know if Mars Direct really works then someone could start a petition that this program really comes to life and that Zubrin becomes in charge of it and that people really start walking on Mars in next 10 years. If from what Zubrin said NASA wouldn't even need to excel it's current budget so in theory it wouldn't be such a big financial deal.

I mean few months ago someone put a petition on white house pages about disclosing UFOs and it was covered in newspapers all over the world and White House promised to response if certain number of signatures was collected. So maybe Mars Direct could be started this way...

louis · 2012-01-04 13:54:18

Lobster wrote:

You know if Mars Direct really works then someone could start a petition that this program really comes to life and that Zubrin becomes in charge of it and that people really start walking on Mars in next 10 years. If from what Zubrin said NASA wouldn't even need to excel it's current budget so in theory it wouldn't be such a big financial deal.
I mean few months ago someone put a petition on white house pages about disclosing UFOs and it was covered in newspapers all over the world and White House promised to response if certain number of signatures was collected. So maybe Mars Direct could be started this way...

I think the Mars project is in effect already under way and it is being led by Elon Musk. I doubt Zubrin has a lot to contribute now although I am a fan of his Roman arch Mars brick architecture for creating pressurised habitats on Mars.

JonClarke · 2012-01-05 03:55:05

Mars direct has been long superceded. Most mission architectures these days are a variant of Mars semi-direct. The next advance might be from people developing water based ISRU.

Last edited by JonClarke (2012-01-05 03:56:45)

JoshNH4H · 2012-01-05 16:25:13

While the most specific technology proposals of Mars Direct may have been superseded, I don't think it's correct to say that the idea of ISRU fuel production (the primary technical difference between Mars Direct and Mars Semi-Direct) is still very much a valid concepts. Despite all of the technical devolopments that have happened in the time since Mars Direct came out, nothing has happened that makes the potential savings in Earth to LEO available from ISRU anything less than highly valuable. This is especially true if you're looking at a mission where you want to take rocket hops around the planet, which has the potential to vastly increase the amount of science and prospecting that the mission can do.

On the other hand, it doesn't appear that launch costs will be the biggest part of the costs of a Mars mission, especially if the rocket is contracted out to someone like SpaceX who will reduce the per-rocket costs to a very low level relative to traditional production techniques.

Let's say we're looking at something like Mars Semi-Direct, which according to astronautix involved 220 tonnes to LEO. At a cost of say $10,000/kg, that's $2.2 billion in launch costs. Now, that's certainly not nothing. On the other hand, based on this essay by Zubrin, which cites a cost estimate by NASA for Mars Direct of $50 billion (1990). Accounting for inflation, that's $82.3 billion today. Launch costs are not a significant part of mission costs. I do believe that this figure includes development for the first mission, in which case the recurring costs would be significantly lower ($20 billion? $15 billion? 5? Less? I simply do not know.) In any case the costs of launching things into LEO is probably not a large part of the costs of a Mars mission.

This is especially true if you account for recent developments in the space launch industry. The Falcon Heavy will launch 53,000 kg for $80 million-$125 million. That's $1500-$2350/kg. At those rates, the launch costs for Mars Semi-Direct would be between $330 million and $517 million. Still a lot of money, but nowhere near what we're talking about in terms of development and recurring costs.

louis · 2012-01-05 16:39:22

JoshNH4H wrote:

While the most specific technology proposals of Mars Direct may have been superseded, I don't think it's correct to say that the idea of ISRU fuel production (the primary technical difference between Mars Direct and Mars Semi-Direct) is still very much a valid concepts. Despite all of the technical devolopments that have happened in the time since Mars Direct came out, nothing has happened that makes the potential savings in Earth to LEO available from ISRU anything less than highly valuable. This is especially true if you're looking at a mission where you want to take rocket hops around the planet, which has the potential to vastly increase the amount of science and prospecting that the mission can do.
On the other hand, it doesn't appear that launch costs will be the biggest part of the costs of a Mars mission, especially if the rocket is contracted out to someone like SpaceX who will reduce the per-rocket costs to a very low level relative to traditional production techniques.
Let's say we're looking at something like Mars Semi-Direct, which according to astronautix involved 220 tonnes to LEO. At a cost of say $10,000/kg, that's $2.2 billion in launch costs. Now, that's certainly not nothing. On the other hand, based on this essay by Zubrin, which cites a cost estimate by NASA for Mars Direct of $50 billion (1990). Accounting for inflation, that's $82.3 billion today. Launch costs are not a significant part of mission costs. I do believe that this figure includes development for the first mission, in which case the recurring costs would be significantly lower ($20 billion? $15 billion? 5? Less? I simply do not know.) In any case the costs of launching things into LEO is probably not a large part of the costs of a Mars mission.
This is especially true if you account for recent developments in the space launch industry. The Falcon Heavy will launch 53,000 kg for $80 million-$125 million. That's $1500-$2350/kg. At those rates, the launch costs for Mars Semi-Direct would be between $330 million and $517 million. Still a lot of money, but nowhere near what we're talking about in terms of development and recurring costs.

This is all absolutely so, Josh, which makes it all the more amazing that NASA and ESA talk about a Mars mission as though it is something beyond the reach of humankind for many decades to come.

My own thoughts about a Mars mission, are in terms of something like 200-250 tonnes to LEO, all told. I think the first mission could easily realise surplus revenue of over a billion dollars, so - taking out the MTCV/EDL/Habitat/ISRU development costs - there is no doubt I think that the operational costs of the first mission will be covered.

JoshNH4H · 2012-01-05 17:41:43

I don't understand how your conclusion follows from my post. I was only talking about launch costs and their relation to the cost of the mission as a whole. I did not give any solid numbers of any kind for the recurring costs of a mission (my estimate was between five billion and 20 billion dollars recurring cost each mission, with a statement that I have absolutely no idea and it could be more or less and it would not surprise me at all).

There's a big difference between launch costs and total mission costs. That was if anything the point of my post. I don't know how that validates your statement that it's possible to come up with a billion dollars of effectively free cash each mission, or your statement that the operating costs of each mission can be covered with a billion dollars of cash.

If anything, the vague cost estimates I gave in my post amount to a disagreement with what you just said in your post.

JoshNH4H · 2012-01-05 17:51:34

By the way, louis, I know I said I plan to respond to your thread in politics and economics, and I do plan to, I actually have the reply page up in another window, but I have somewhat limited time and if I don't write the small replies it'll never happen. It'll get written, I promise!

louis · 2012-01-05 18:16:13

JoshNH4H wrote:

I don't understand how your conclusion follows from my post. I was only talking about launch costs and their relation to the cost of the mission as a whole. I did not give any solid numbers of any kind for the recurring costs of a mission (my estimate was between five billion and 20 billion dollars recurring cost each mission, with a statement that I have absolutely no idea and it could be more or less and it would not surprise me at all).
There's a big difference between launch costs and total mission costs. That was if anything the point of my post. I don't know how that validates your statement that it's possible to come up with a billion dollars of effectively free cash each mission, or your statement that the operating costs of each mission can be covered with a billion dollars of cash.
If anything, the vague cost estimates I gave in my post amount to a disagreement with what you just said in your post.

Josh - I tend to use a ready reckoner for mission costs. I can't exactly provide a rational justification for it, but it seems to work fairly well I think, in that I think that's what people seem to be coming round to. I take the cost to LEO and multiply by 4. So if Space X can get you to LEO for $5000 per kg, that's $20,000 per kg for your Mars mission (assuming basic development costs have been written off).

Any cost analysis needs to take in a number of factors:

1. Amortisation of the big infrastructure costs. For example if you build your MTV and you can use it safely for say ten missions (why not? - the ISS seems to be surviving for decades). Then you might need to think in terms of dividing the cost over ten missions (of course depends whether you are having to borrow the capital cost, or whether someone is providing it interest free) .

2. Reduced tonnage requirements for life support. As the Mars colony develops, the cost of keeping people alive on Mars and in transit should reduce. The Mars colony should be producing its own oxygen, food, rocket fuel, energy etc.

3. Cost to LEO.

4. Gross and net revenue from trade and sponsorship etc. Eg. meteorite sales back on Earth.

5. Hidden and open subsidies.

Taking everything together, I feel if a mission only requires 250 tonnes to LEO, then it is very, very doable with (mostly) current technology. I think Musk agrees and I think that is what he is working towards.

JoshNH4H · 2012-01-05 20:03:04

I see that that post was in English... yet nary a thing within it made any sense. Firstly, I would like to quote something which I think says a lot about your methodology for estimating prices:

I tend to use a ready reckoner for mission costs. I can't exactly provide a rational justification for it

Translation: He made it up. The mission cost estimates provided by louis are not based in reality, fact, history, or even on extrapolation. It's simple fantasy. His chosen estimator? Four times the launch costs. Even though the launch costs do not have a significant connection to total mission costs. Just because cheaper rockets have been developed does not mean that the price of the mission as a whole automatically goes down by that same factor. I cannot think of any reason at all why it would. On a related note, louis' estimate of 250 tonnes to LEO cannot be given any credence either, because he doesn't know how to calculate how much mass you need in LEO to get something to LMO (Or else he would do it himself ad not ask us to, right?). He says that people seem to be coming around to his method of estimating costs. So far as I know, this is categorically false. I have not seen one person other than louis estimate costs in that way. Further, the costs which he comes to by estimating in that way are not in any way in line with the cost estimates produced by other methods. Even if you subtract 2 billion dollars from the estimated cost of Mars Direct, the cost is 81 billion dollars for the first mission. Louis' method's estimate for that same mission? 4.4 billion dollars. There is a gigantic discrepancy here, which cannot be handwaved away.

Talking about initial exploration missions, points 2 and probably 4 are irrelevant (regardless of what louis says, revenue generated by an initial mission will not be anything near enough to cover launch costs and the cost to the capability of the mission will probably make it not worth it). 3 is simple. 1 misuses the word "amortization," which has more to do with accounting than actual reuse of mission hardware. 5 has another name; this is "The cost of the mission"- since initial exploration missions will almost certainly be done on a government's checkbook. Further, he doesn't seem to account in this list for important things, such as the per-mission cost of hardware and on-the-ground costs like support/operations and facility maintenance.

He then invokes Elon Musk, claiming on blatant supposition (remember, there was not a single link, citation, or reference provided at any point during his post)

louis · 2012-01-05 20:48:27

JoshNH4H wrote:

I see that that post was in English... yet nary a thing within it made any sense. Firstly, I would like to quote something which I think says a lot about your methodology for estimating prices:
I tend to use a ready reckoner for mission costs. I can't exactly provide a rational justification for it
Translation: He made it up. The mission cost estimates provided by louis are not based in reality, fact, history, or even on extrapolation. It's simple fantasy. His chosen estimator? Four times the launch costs. Even though the launch costs do not have a significant connection to total mission costs. Just because cheaper rockets have been developed does not mean that the price of the mission as a whole automatically goes down by that same factor. I cannot think of any reason at all why it would. On a related note, louis' estimate of 250 tonnes to LEO cannot be given any credence either, because he doesn't know how to calculate how much mass you need in LEO to get something to LMO (Or else he would do it himself ad not ask us to, right?). He says that people seem to be coming around to his method of estimating costs. So far as I know, this is categorically false. I have not seen one person other than louis estimate costs in that way. Further, the costs which he comes to by estimating in that way are not in any way in line with the cost estimates produced by other methods. Even if you subtract 2 billion dollars from the estimated cost of Mars Direct, the cost is 81 billion dollars for the first mission. Louis' method's estimate for that same mission? 4.4 billion dollars. There is a gigantic discrepancy here, which cannot be handwaved away.
Talking about initial exploration missions, points 2 and probably 4 are irrelevant (regardless of what louis says, revenue generated by an initial mission will not be anything near enough to cover launch costs and the cost to the capability of the mission will probably make it not worth it). 3 is simple. 1 misuses the word "amortization," which has more to do with accounting than actual reuse of mission hardware. 5 has another name; this is "The cost of the mission"- since initial exploration missions will almost certainly be done on a government's checkbook. Further, he doesn't seem to account in this list for important things, such as the per-mission cost of hardware and on-the-ground costs like support/operations and facility maintenance.
He then invokes Elon Musk, claiming on blatant supposition (remember, there was not a single link, citation, or reference provided at any point during his post)

You should develop a sense of humour Josh - it can help in relating to people. Politeness is also helpful.

My "ready reckoner" wasn't something I plucked out of the air - I've read loads about Mars mission costs ,probably a few hundred thousand words at least. It was on the basis of my reading that I came up with the times four figure. It certainly isn't going to be LESS than the cost to LEO. The cost of travel to Mars is probably not that expensive per se...but you have to account for MTV costs. And then there's EDL costs, habitat and ascent/return. Four times feels right to me.

You are of course wrong to suggest that the launch costs don't run through to other costs. If launch costs are like the $200 per kg (!) Musk is now talking about then everything changes. Then - just as ONE example - you can afford to take cheap, basic PV panels to Mars, rather than state of the art, million dollar per sq. metre PV panels. Then you don't need to invest in expensive ISRU projects - you just take the raw materials to Mars - "simples" as we say in the UK.

So at every level launch costs are absolutely crucial - in other words my multiplier is very much justified.

I never said people were coming round to my METHOD of calculating costs - I was simply inidicating that my x 4 factor seemed to give you something like where people were now placing their estimates - in terms of operational costs. If you read my posts, you will know I always (quite correctly - people who don't are the idiots) distinguish between initial one time capital costs and operational costs. A few years back when I used to give these same estimates people used to laugh in my face. Now they have to laugh in Musk's face as well.

Your analysis of my five cost factor points is pathetic. The idea that your framework is going to a single footprint mission is absurd. The important cost analysis is whether following the initial capital outlay you can cover subsequent operational costs. If you don't understand these distinctions I don't hold out too much hope for you. :)

Clearly Musk thinks we can get to Mars in the same sort of timeframe that I am thinking of - 10-20 years:

http://www.universetoday.com/88060/spac … ur-future/

"Further, he doesn't seem to account in this list for important things, such as the per-mission cost of hardware and on-the-ground costs like support/operations and facility maintenance." Er - what do you think "launch costs" mean? If I ask Space X to put a satellite into orbit for me I pay them for that - I don't expect to be presented with a separate bill for their rocket hardware and ground control ops. Duh!!

JoshNH4H · 2012-01-05 23:19:44

Care to come up with a citation showing your "ready reckoner" actually comes up with numbers that work? It's not like you're alone in having done a lot of research on Mars missions.

Further, given the fairly small proportion of total costs which are launch costs (in cost estimates which come from informed professionals), it would make some sense to do that kind of thing anyway. I must come back to your most direct statement of why you chose four times launch costs: It "feels right" to you. I don't know what that is, but it's not a valid method of estimating costs.

To allege that the cost reduction will be linear with regards to launch costs is really quite untrue. That depends on a lot of different factors. Unless you've done an incredibly complex analysis I don't believe that it's predictable. Further, I don't know how you would extract that from any amount of reading, seeing as just about all cost estimates of which I'm aware, firstly, do not make the assumed Earth-to-Orbit costs easy to figure out, and secondly tend to assume a fairly standard EELV-based launcher which would have costs in the same general region.

I do not mean rocket hardware. I mean equipment hardware. Habs, rovers, spacesuits, ERVs, MTVs, nuclear reactors (or solar panels, we have other things to debate at the moment) communications satellites, ISRU equipment where applicable, and all of the other hardware required for a mission. Likewise, SpaceX will not be advising the mission on where to collect samples, what to do if something goes wrong on the way, etc. Plus development to make the mission technology better from mission to mission; we saw it on Apollo and they did it because it makes sense.

Can you cite where I suggested a framework of flags and footprints? I would have the first few missions involve robust exploration and prospecting which would lay the foundation for colonization, which would commence just a few years later.

I have nothing but respect for you, and I absolutely value your input and the discussions we have based on it. However, this does not mean that I'm going to be anything less than honest when you're saying something that is simply wrong.

Hop · 2012-01-06 14:36:40

JoshNH4H wrote:

While the most specific technology proposals of Mars Direct may have been superseded, I don't think it's correct to say that the idea of ISRU fuel production (the primary technical difference between Mars Direct and Mars Semi-Direct) is still very much a valid concepts.

The Mars Semi-Direct plans I've seen call for ISRU fuel.

JoshNH4H · 2012-01-07 00:11:02

Hop-

I'm not too familiar with Mars Semi-Direct. It was my understanding that it was a very similar mission to Mars Direct except insofar as it advocated for the return fuel to be sent with the mission. Is this incorrect?

Rune · 2012-01-07 08:56:06

On Mars semi-direct (also known as Design Reference Mission 3.0):

Basically, the MAV is smaller and only gets to LMO so the ISRU plant is smaller and you don't need a nuke on the ground (or a football field of solar panels). Of course, that makes the MTV bigger and required to last for the entire mission, which poses its own set of problems, like liquid cryogenic storage of fuels for years. And they still baseline nuclear thermal reactors for the engines. Nuts in my opinion if they choose hydrogen as the propellant.

With something else as propellant (methane? even plain water would do if you accept standard H2/LOX mass ratios) and some fuel delivery form the mars surface in a bigger MAV (perhaps optional to allow visits to Phobos and Deimos, or propulsively braking into earth's orbit), it would make more sense, IMO. Why fear a nuclear surface system rated at kilowatts if you have a NERVA-class engine waiting in orbit to take you home, rated at megawatts.

Technically speaking, btw, that one is in my humble opinion both a simpler and lighter option compared with chemical engines that require cryogenic propellant management for years and either absurdly high mass ratios or plenty of staging. In any case, more starting mass with more complex and numerous systems that are mission-critical and just thrown away after the mission is done.

Rune. It's a bit of an old tech, though... more plumbing than aerospace work.

Mark Friedenbach · 2012-01-07 12:37:06

Mars Direct is simpler, safer, and easier to pull off than DRM 3.0. The DRM was in response to MD, but added the complexity of a transfer vehicle left in Mars orbit. IIRC Zubrin spends a section in the Case for Mars discussing the problems of this approach that I won't reiterate here, but another big one that Rune didn't mention is the lack of artificial gravity on the way out. One can only speculate as to why.

It's all moot though as they way this works is that every few years some engineers working under political pressure at JSC come up with a reference mission, and then anyone within the agency or government has to use this mission as the bible for what a minimum human-to-Mars programme would look like. The current DRM is unpublished Constellation-era framework that called for multiple (!!) Ares V launches per mission, with some crazy number like 300-400 tonnes to LEO, and all for just a few weeks at a single spot on the surface. Unfortunately it's unpublished (unfinished?), but of course being the JSC-approved reference mission, it was taken at face value the only design considered by the Augustine commission, who of course said it was ridiculously expensive and put Mars off the table for the foreseeable future.

Last edited by Mark Friedenbach (2012-01-07 12:38:00)

Rune · 2012-01-07 13:21:11

Mark Friedenbach wrote:

Mars Direct is simpler, safer, and easier to pull off than DRM 3.0. The DRM was in response to MD, but added the complexity of a transfer vehicle left in Mars orbit. IIRC Zubrin spends a section in the Case for Mars discussing the problems of this approach that I won't reiterate here, but another big one that Rune didn't mention is the lack of artificial gravity on the way out. One can only speculate as to why.

Oh, I won't argue with you there. MD is the simplest, easiest way you can go about it. Especially if you restrict yourself to non-nuclear propulsion. Just one thing I don't quite get... you are saying I omitted that DRM3.0 hasn't got artificial gravity on the way back? Because it doesn't really have artificial gravity at any stage of the flight. Like the original MD. The revised MD, I believe, only has it on the Mars bound leg. Anyhow, silly point, since it could be easily added to a big MTV like the one DRM 3.0 has, and even to the return vehicle in MD, I'm sure. If it's even required at all, that is.

About it being safer... well, it's more optimistic, no two ways about that. In everything from mass manifest to contingencies. I can say "mine" reuses more, and the MTV can be flight-tested on a cargo flight, and I will leave it at that.

Rune. Imagine if a country owned a vehicle capable of going to mars and back, and be reused. They would be forced to use it several times!

Hop · 2012-01-07 13:36:33

Mark Friedenbach wrote:

Mars Direct is simpler, safer, and easier to pull off than DRM 3.0. The DRM was in response to MD, but added the complexity of a transfer vehicle left in Mars orbit. IIRC Zubrin spends a section in the Case for Mars discussing the problems of this approach that I won't reiterate here, but another big one that Rune didn't mention is the lack of artificial gravity on the way out. One can only speculate as to why.
It's all moot though as they way this works is that every few years some engineers working under political pressure at JSC come up with a reference mission, and then anyone within the agency or government has to use this mission as the bible for what a minimum human-to-Mars programme would look like. The current DRM is unpublished Constellation-era framework that called for multiple (!!) Ares V launches per mission, with some crazy number like 300-400 tonnes to LEO, and all for just a few weeks at a single spot on the surface. Unfortunately it's unpublished (unfinished?), but of course being the JSC-approved reference mission, it was taken at face value the only design considered by the Augustine commission, who of course said it was ridiculously expensive and put Mars off the table for the foreseeable future.

For reference, here is one flavor of Mars Semi-Direct: A Practical Architecture for Exploration-Focused Manned Mars Missions Using Chemical Propulsion, Solar Power Generation and In-Situ Resource Utilisation by Willson and Clarke

The author Clarke I believe is the same Jon Clarke participating in this thread.

---

A few notes on the Mars Semi-Direct in Willson & Clarke's pdf:

694 tonnes to LEO (on the page labeled 202)

ERV propellant isn't deep cryogenic nor is the ERV NTR. The itemized mass list includes 44.22 tonnes of liquid oxygen and liquid methane (on the page labeled 200).

Lifting an ERV off Mars' surface and sending on a Trans Earth Injection (TEI) is very challenging. To crack enough propellant, you'd need a very robust plant and power source. ISRU to provide enough propellant to get an MAV to Mars orbit is more doable. In this regard, I regard Mars Semi-Direct more plausible than Mars Direct.

Willson & Clarke have under-estimated the delta V to get from low Mars orbit to Phobos. Thus their mission plan has insufficient propellant to make their side trip to Phobos and achieve TEI. Their plan would kill the astronauts. However if they cut out the side trip to Phobos, their propellant is sufficient.

There is some controversy on the radiation shielding need to protect against GCR (galactic cosmic rays). In my opinion Willson and Clarke's radiation shielding is insufficient.

---

I haven't seen an itemized mass list of Mars Direct payloads as Willson and Clarke have done for Mars semi-direct. Given that propellant for the return trip would be from Mars, you can take 40 tonnes off the MTV as well as the ERV. But the ERV and MTV are two separate vehicles. The MTV and hab would be the same payload in MD. I would think you'd need to land a cargo vehicle just as W & C call for in MSD. And you'd need to have Trans Mars Stages (TMS) to send the MTV, ERV and cargo vehicles on their ways.

So I believe MD would also require multiple Ares V launches (or multiple SLS launches, since Constellation bit the dust).

Valeri Polyakov demonstrated 8 months of weightlessness isn't a show stopper. So I don't regard MSD sans bolo MTV as a major flaw.

Last edited by Hop (2012-01-07 13:39:50)

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