Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

Dayton3 · 2004-11-27 09:42:47

I've seen some objections to Mars Direct raised over the years and I've wondered if Dr. Zubrin has addressed them directly.

Questions such as:

1) What about the allegation that his mass estimates for the equipment and supplies necessary to support a crew on Mars are too low?

2) Is the proposed ERV really large enough for four astronauts for six months?

3) How does he address the new projections of radiation on the Martian surface being significantly higher than originally thought?

4) If NASA insisted on a six man crew per mission, how much larger would his Ares type booster need to be to get the job done?

Just some questions.

RobertDyck · 2004-11-27 11:02:21

Radiation on Mars surface is roughly half that of ISS. Mars orbit is double ISS, but Mars has an atmosphere. His design included bags of regolith (Mars soil) covering the habitat roof. That is still sufficient radiation shielding. He did address the radiation question as soon as reporters covered results from the Marie instrument on Mars Odyssey, and pointed out the fact that reporters looked at orbital numbers, not surface numbers.

Objections about the ERV: he announced a Mars Society prize at the 2003 convention to redesign the ERV. Did you create an entry?

Mass estimates too low? He points out that NASA's DRM includes carrying propellant for the return trip all the way from Earth. That significantly increases mass. That's why he calls the DRM "Semi-Direct".

His design in 1990 included water and oxygen recycling with 80% efficiency; the Johnson Space Center's Advanced Life Support Project already achieved 97% water recycling efficiency. In "The Case for Mars" he stated NASA wanted to see 95% efficiency in water and oxygen recycling, but if we waited for that we wouldn't be ready until the 21st century! Wait a minute, it is the 21st century now. It appears we pissed away so much time the 21st century caught up with us. We now have the high efficiency recycling systems that NASA wants, so we can go now. But as for mass estimates, that reduces consumables below Robert's estimates.

NASA also plans for extensive suit consumables for EVA. I haven't heard Robert's response, but the original silver-zinc battery for the EMU (Shuttle spacesuit) only lasts 6 EVAs. A study in 1999 proposed an upgraded silver-zinc battery that would last 30 EVAs, but the cost was too high. Current lithium-ion batteries would last so long you could take every suit on EVA every sol on Mars and it would still only use half its life. Consumables also include LiOH for scrubbing CO2, but the upgraded EMU for ISS already uses Ag2O as a regenerable sorbent. It could be made lighter by replacing the sheets with granules, and reduce power by replacing the electric oven with a microwave, but its already reusable. A mechanical counter pressure suit uses sweat to cool rather than a water sublimator. That means drinking water is the only suit consumable. The cold of Mars would reduce cooling requirement. All this dramatically reduces mass of suit consumables, bringing it in line with Robert's estimates.

Dayton3 · 2004-11-27 12:56:28

Radiation on Mars surface is roughly half that of ISS. Mars orbit is double ISS, but Mars has an atmosphere. His design included bags of regolith (Mars soil) covering the habitat roof. That is still sufficient radiation shielding. He did address the radiation question as soon as reporters covered results from the Marie instrument on Mars Odyssey, and pointed out the fact that reporters looked at orbital numbers, not surface numbers.
Objections about the ERV: he announced a Mars Society prize at the 2003 convention to redesign the ERV. Did you create an entry?
Mass estimates too low? He points out that NASA's DRM includes carrying propellant for the return trip all the way from Earth. That significantly increases mass. That's why he calls the DRM "Semi-Direct".
His design in 1990 included water and oxygen recycling with 80% efficiency; the Johnson Space Center's Advanced Life Support Project already achieved 97% water recycling efficiency. In "The Case for Mars" he stated NASA wanted to see 95% efficiency in water and oxygen recycling, but if we waited for that we wouldn't be ready until the 21st century! Wait a minute, it is the 21st century now. It appears we pissed away so much time the 21st century caught up with us. We now have the high efficiency recycling systems that NASA wants, so we can go now. But as for mass estimates, that reduces consumables below Robert's estimates.
NASA also plans for extensive suit consumables for EVA. I haven't heard Robert's response, but the original silver-zinc battery for the EMU (Shuttle spacesuit) only lasts 6 EVAs. A study in 1999 proposed an upgraded silver-zinc battery that would last 30 EVAs, but the cost was too high. Current lithium-ion batteries would last so long you could take every suit on EVA ever sol on Mars and it would still only use half its life. Consumables also include LiOH for scrubbing CO2, but the upgraded EMU for ISS already uses Ag2O as a regenerable sorbent. It could be made lighter by replacing the sheets with granules, and reduce power by replacing the electric oven with a microwave, but its already reusable. A mechanical counter pressure suit uses sweat to cool rather than a water sublimator. That means drinking water is the only suit consumable. The cold of Mars would reduce cooling requirement. All this dramatically reduces mass of suit consumables, bringing it in line with Robert's estimates.

Interesting information. Thanks. It appears that once again, Dr. Zubrin has crossed all the t's and dotted all the i's.

Dr. Robert Zubrin should be the NASA Admin. in my opinion.

I'm no scientist. Merely a history teacher and football coach. So I can't redesign the ERV. Though IIRC, I thought the original Mars Direct ERV was supposed to be capable of teathering off from the lower stage after escape from Mars and generating artificial gravity just like the Hab module does on the outbound trip.

On the other hand, if Earth Return takes place in zerio G, more of the internal volume of the ERV because usable as space and it would be possible for the astronauts to conduct the occasional EVA on the way back as a way of relieving boredom.

John Creighton · 2004-11-27 13:26:05

Why do people want a greater mass budget? Is it for safety or is it so more can be accomplished on mars? Mars direct has several different delivery stages. One can start with a mars direct architecture and add extra supplies as needed. The astronauts be contracted for a one year stay but they can get significant bonuses each year longer that they stay provided they are good workers. The bonuses will be clearly justified by the money that will be saved by not sending another crew. The astronauts can choose to keep the money for themselves when/if they come home or they can use it to help out their family back home. This way the astronaut is given incentive beyond doing good for there country or humanity. This way the astronaut will not feel like they are abandoned. The mass beget can be increased by increasing the amount of supply drops. Not a problem. I just started a discussion comparing the cost of a one way mars mission to resuplying the ISS

RobS · 2004-11-27 15:46:30

One problem he has acknowledged is that pressurized rovers require more mass than is available in the Hab. But maybe greater recycling, reducing the consumable mass, has partially solved that problem.

There is no big push at the moment to rewrite Mars Direct. You can't rewrite something like that every few years because then no one knows exactly what your advocating. You are better off advocating Mars Direct as a series of principles and rewriting the design when it might actually get implemented.

One change I would make, if one had a bigger booster, would be to send the ERV and the Hab more or less together, so the ERV can serve as a backup to the Hab in an emergency (the way the LM did in Apollo 13).

Once you start redesigning, there's no telling where it will stop. You might end up with an interplanetary transit vehicle and a Mars ascent vehicle, for example.

-- RobS

John Creighton · 2004-11-27 15:59:39

It is nice to be able to discus some alternatives though to give the politicians some flexibility to suite there goals.

Once you start redesigning, there's no telling where it will stop. You might end up with an interplanetary transit vehicle and a Mars ascent vehicle, for example.

Maybe PRATT & WHITNEY'shttp://www.nuclearspace.com/A_PWrussview_FINX.htm]triton would make a good interplanetary transit vehicle.

Anyway I prefer an exploration strategy to mars direct. I like the planetary societies approach because the steps are much more incremental and it accomplishes a lot of science objectives at each step. But anyway what is wrong with advocating a series of plans and saying which one is your favorite. I want to get into space how we do it is just details.http://www.planetary.org/news/2004/cev-development-0722.html]http://www.planetary.org/news/2004/cev- … -0722.html

RobertDyck · 2004-11-27 17:08:47

Once you start redesigning, there's no telling where it will stop. You might end up with an interplanetary transit vehicle and a Mars ascent vehicle, for example.

Nothing wrong with that. It is where I ended up. There's one congressman who wants a reusable ITV and is willing to push to fund a manned Mars program if it includes one.

BWhite · 2004-11-27 18:05:21

Rover mass too large?

Add a launch and pre-position a big rover.

Grypd · 2004-11-27 18:25:44

The one question that I have always thought is the deathknell of the mars direct program is.

5) Is mars direct just not an expanded Apollo program and that after a few missions and with public interest becoming less it will be cancelled just as fast as the apollo missions where.

RobertDyck · 2004-11-27 18:35:28

Is mars direct just not an expanded Apollo program and that after a few missions and with public interest becoming less it will be cancelled just as fast as the apollo missions where.

That's one reason I'ld like to see a reusable Earth-to-LEO space taxi, reusable ITV, and construction of a permanent base start with the first manned mission

Euler · 2004-11-27 18:37:55

The ERV is clearly the biggest problem with Mars Direct. Its a manned interplanetary launch vehicle that needs a landing system for Mars, a nuclear power plant, chemical feedstock, a self-fueling system, fuel tanks, rocket engines, a crew compartment, radiation shielding, consumables, some way of landing on Earth, etc. There is a limit to how small and light you can make all of that, but in the Mars Direct plan it all has to weigh less than 30 tons. I am not convinced that we could make the ERV that light, and even if we could it would be very expensive and there would be a lot of things that could go wrong.

That is why NASA's Mars Reference Mission (a.k.a. Mars Semi-Direct) replaces the surface ERV with a simple Mars Assent Vehicle, and puts the ERV in orbit. This would require 3 launches per mission instead of 2, but it would make it much easier to stay within the allowed weight limit.

Dayton3 · 2004-11-27 20:10:11

The ERV is clearly the biggest problem with Mars Direct. Its a manned interplanetary launch vehicle that needs a landing system for Mars, a nuclear power plant, chemical feedstock, a self-fueling system, fuel tanks, rocket engines, a crew compartment, radiation shielding, consumables, some way of landing on Earth, etc. There is a limit to how small and light you can make all of that, but in the Mars Direct plan it all has to weigh less than 30 tons. I am not convinced that we could make the ERV that light, and even if we could it would be very expensive and there would be a lot of things that could go wrong.
That is why NASA's Mars Reference Mission (a.k.a. Mars Semi-Direct) replaces the surface ERV with a simple Mars Assent Vehicle, and puts the ERV in orbit. This would require 3 launches per mission instead of 2, but it would make it much easier to stay within the allowed weight limit.

I wonder if going to Mars Semi-Direct would allow Dr. Zubrins proposed fully enclosed, life supporting rover to be included?

I understand why Dr. Zubrin liked the idea of a rover allowing shirtsleaved operations. The rover effectively becomes yet another "life boat" option on the Mars surface in case of a catastrophic failure of life support in the Hab.

But as far as exploration is concerned, the first missions could probably have plenty to do with a couple of internal combustion driven "Apollo type" rovers.

RobS · 2004-11-27 22:17:07

Well, yes, Robert, both you and I favor an interplanetary transit vehicle. As for prepositioning a large pressurized rover, that is better than no pressurized rover at all, but it does not solve a problem with Mars Direct: that the Hab might not land near an ERV and you need a vehicle to drive over to it.

As for starting with a base on the first mission: dream on. Congress won't approve that kind of funding. Besides, Mars exploration is more likely to work if it is incremental; you start with a few 18-month missions, settle on a place for a "Mars McMurdo," have some crew stay through two oppositions, begin to build up a central base, etc.

-- RobS

BWhite · 2004-11-28 02:05:28

Well, yes, Robert, both you and I favor an interplanetary transit vehicle. As for prepositioning a large pressurized rover, that is better than no pressurized rover at all, but it does not solve a problem with Mars Direct: that the Hab might not land near an ERV and you need a vehicle to drive over to it.
As for starting with a base on the first mission: dream on. Congress won't approve that kind of funding. Besides, Mars exploration is more likely to work if it is incremental; you start with a few 18-month missions, settle on a place for a "Mars McMurdo," have some crew stay through two oppositions, begin to build up a central base, etc.
-- RobS

As with the basic plan, rover #2 and ERV #2 stay in Mars orbit until the Mars One crew makes contact with the ERV and rover that were pre-positioned.

John Creighton · 2004-11-28 12:26:44

As for prepositioning a large pressurized rover, that is better than no pressurized rover at all, but it does not solve a problem with Mars Direct: that the Hab might not land near an ERV and you need a vehicle to drive over to it.

What if it could drive itself? I think that would add an extra level of reduncancy. The could meet the pressurized rover half way in their unpresurized rover. Worst case they will stink because they spent way too long in there preassure suit.

Mark S · 2004-11-28 18:29:12

4) If NASA insisted on a six man crew per mission, how much larger would his Ares type booster need to be to get the job done?

In NASA's original Design Reference Mission, a 200 MT booster is specified. The booster chosen was a Saturn V-derivative sometimes referred to as "Comet." It would have two strap-on boosters (each with two F-1's,) six J-2's on stage 2, and a wider 3rd stage. In the end, it doesn't look much like a Saturn V aside from the same diameter tankage and same types of engines.

In later versions of the DRM, the Comet was replaced with Magnum, an in-line SDV. Orbital Sciences' VSE proposal shows a similar booster. Magnum would only lift 80 MT, and the spacecraft and its TMI stage would be launched on separate Magnums (meaning six launches instead of three.)

Mark S · 2004-11-28 18:48:05

One problem he has acknowledged is that pressurized rovers require more mass than is available in the Hab.

If you've ever seen the artwork for James Cameron's Mars project, the famed movie director comes up with a novel solution: land the crew inside the pressurized rover.

Is it workable? Who knows. But at least we have people thinking about innovative design techniques that deserve to be studied.

Grypd · 2004-11-28 20:21:13

How about the pressurised rovers having the pressurised section inflatable. That should solve that issue.

Shaun Barrett · 2004-11-29 02:15:22

How low can we get the Pressurised Rover's mass, perhaps using new materials, before we lose too many desirable features and compromise reliability and safety?
???

SpaceNut · 2004-11-29 07:01:34

Another thought is that since we are on a very long duration from orbit to orbit I would assume we will be needing a set of space suits for any repairs that must be made. Those suits would be different from those that would be used on the martian surface.

GCNRevenger · 2004-11-29 10:00:48

Interesting information. Thanks. It appears that once again, Dr. Zubrin has crossed all the t's and dotted all the i's.
Dr. Robert Zubrin should be the NASA Admin. in my opinion.

Zubrin has done no such thing, MarsDirect is still too optimistic in its mass budgets in the ERV and the HAB vehicle. Improved LSS efficency, packing fewer suit batteries, knocking off a few kilos here and there... Its all nickle and dime stuff. The core problem is and remains that Ares is too small for a two-launch mission.

The threat from cosmic radiation may also be greater then once thought, with recent studies into cataract problems from even modest doses, which could bump up the mass of both vehicles several tons, since they won't have the bennefit for Martian air and dirt when traveling to and from Mars.

If the ERV/MAV is a seperate vehicle from the HAB module/lander, then carrying the long range rover in the initial vehicle is non-negotiable, the risk of landing error with today's technology is too great.

RobertDyck · 2004-11-29 10:42:34

Zubrin has done no such thing, MarsDirect is still too optimistic in its mass budgets in the ERV and the HAB vehicle. Improved LSS efficency, packing fewer suit batteries, knocking off a few kilos here and there... Its all nickle and dime stuff. The core problem is and remains that Ares is too small for a two-launch mission.

Could you please give specifics regarding "too optimistic mass budget". I wouldn't argue that Mars Direct needs to be updated with latest technology, but as others on this board have pointed out to me we need a consistent message to congress. In his testimony before congress, Dr. Zubrin himself advocated starting with a study for the best mission plan. But I still haven't heard how Mars Direct couldn't fit on two Ares launches.

Mark S · 2004-11-29 17:56:35

I too believe that Mars Direct is too optimistic in its mass budgets. I knew some people who took part in the Kepler competition, and they said so explicitly. I haven't read their report yet, but I soon will, and I doubt the verdict will be pretty regarding the feasibility of Mars Direct.

Michael Bloxham · 2004-11-29 20:59:22

Reduce the crew to 3. -All problems solved.

Shaun Barrett · 2004-11-29 21:02:57

Aahhh .. you're all nuts!!! :angry:

If Dr. Z says Mars Direct is feasible (albeit with slight modifications) and Robert Dyck thinks he can make it work, that's good enough for me!

When do we leave?!! ??? [ :laugh: ]

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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

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Re: Has Dr. Zubrin Addressed Mars Direct Objections? - A few questions?

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