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

GCNRevenger · 2004-12-05 01:07:46

I will restate that my largest complaint about MarsDirect is not any particular detail, but the way that it was designed. That the desperate need to make an acceptable Mars mission as small and cheap as possible for the zeal and sake getting humans to Mars has led to a design that is not acceptable or practical. It is so over-optimistic in its "sales pitch" in cost, size, and capability that that it defies credible consideration. $6-8Bn is silly, even the ~$20ish for development is probobly too low. The vehicles are too small. The rover budget is too small. The reactor(s) budget is too small. And so on and so forth... but the central problem remains:

The mission is designed with the wrong basic methodology, that the launch vehicle was bascially selected first since it would be a major expense and Ares was cheaper and quicker, then the vehicle was designed and it all had to ride in only two shots to save money, and then whatever mission could be squeezed out of it became the proposed mission.

And the mission as proposed does nothing very well: the crew and science payload is too small (Sagan)... the radiation shielding, physical size, and misc. equipment margins are too small (Von Braun)... and the arcitecture has low marginal payload masses versus a more powerful rocket, small crew too etcetera (O'Neill).

The whole concept of a direct flight non-colonizing Mars mission has to be looked at from the other direction, that the mission requirements are determined first, then the vehicle(s) designed to fill those requirements, and then a launch vehicle (or two, payload + TMI) is selected.

Dook · 2004-12-05 07:31:15

If we have to choose one mission and stick to it, we should choose the http://cmex-www.arc.nasa.gov/CMEX/data/ … ]Reference Mission. It is much more feasable and less risky than Mars Direct, and it is already approved by NASA. $55 Billion is a very reasonable price for a mission that is likely to work.

I wasn't as familiar with the NASA design reference mission as I was with Mars Direct. After some research it seems to basically be Mars Semi-Direct. I'll support it, not that it really matters though.

RobertDyck · 2004-12-05 08:44:20

I will restate that my largest complaint about MarsDirect is not any particular detail, but the way that it was designed. That the desperate need to make an acceptable Mars mission as small and cheap as possible for the zeal and sake getting humans to Mars has led to a design that is not acceptable or practical. It is so over-optimistic in its "sales pitch" in cost, size, and capability that that it defies credible consideration. $6-8Bn is silly, even the ~$20ish for development is probobly too low. The vehicles are too small. The rover budget is too small. The reactor(s) budget is too small. And so on and so forth... but the central problem remains:
The mission is designed with the wrong basic methodology, that the launch vehicle was bascially selected first since it would be a major expense and Ares was cheaper and quicker, then the vehicle was designed and it all had to ride in only two shots to save money, and then whatever mission could be squeezed out of it became the proposed mission.
And the mission as proposed does nothing very well: the crew and science payload is too small (Sagan)... the radiation shielding, physical size, and misc. equipment margins are too small (Von Braun)... and the arcitecture has low marginal payload masses versus a more powerful rocket, small crew too etcetera (O'Neill).
The whole concept of a direct flight non-colonizing Mars mission has to be looked at from the other direction, that the mission requirements are determined first, then the vehicle(s) designed to fill those requirements, and then a launch vehicle (or two, payload + TMI) is selected.

You will always have the constraint of the smallest and cheapest possible. Sure I would like all the money spent on Iraq to be redirected to NASA, but it isn't going to happen. In 2000 the military had a budget of $288 billion and NASA had $14.77 billion. I said at that time we could reduce the military by 10% and give half to NASA, and use the other half for tax cuts. That didn't happen, instead Bush spent $80 billion in 2002 on the war in Iraq and the annual military budget has doubled. NASA received a modest budget increase, that's all we can expect ever will happen. So keeping cost within NASA's current budget is necessary to make it happen.

After 32 years stuck in LEO, if we don't break out now it'll take another 15 years of no progress what so ever before we have another opportunity to start progress out of LEO.

As for designs, Robert Zubrin has a PhD in nuclear engineering so I think he knows how to design a reactor. I believe he chose an existing space-rated reactor, the SP-100. He didn't start with the Ares rocket, he actually started with a bulked-up Shuttle-C that he called Shuttle-Z. He then optimized it for interplanetary missions and the result was Ares. He also said any commercial company with interest in Mars (to win a prize) would use 3 launches of Energia. So he isn't locked into one launch vehicle or number of launches. But keeping cost down is necessary because that's what congress looks at, and without congressional budget approval we're not going anywhere.

Dayton3 · 2004-12-05 09:18:41

Actually, designing the mission around the launcher IS the way things have always been done.

The Saturn V design was frozen BEFORE the Apollo mission architecture was even decided upon.

I stand by my preference. Basic Mars Direct with a 5th crewman launched by NASA "Comet" Saturn V variant which should improve mass margins significantly over the Ares launched Mars Direct.

I'm fully comfortable with the mission carrying less than a ton of scientific instruments. I'm sure there will be plenty of work to do over the 500 days on the Martian surface with that scientific suite.

John Creighton · 2004-12-05 11:09:45

Actually, designing the mission around the launcher IS the way things have always been done.

The design process is all about considering and comparing alternatives. Thus choosing to design the mission around the launcher or the launcher around the mission is one alternative. Depending on the perceived benefit of both options or both options can be explored. Zubrins approach made since at the time. The shuttle was available and could be upgraded to a shuttle C with a minimum of development cost. Whether or not Zubrin made the right choice, it was good he designed for one of the less expensive ways to get to mars. The point was not that it was necessarily the best mission but it was possible to go to mars at a low cost with the technology of the time.

GCNRevenger · 2004-12-05 11:30:25

"You will always have the constraint of the smallest and cheapest possible."

Certainly not, this is absolutely the wrong way to think about building a gainful Mars mission. If you can build a system that is much safer, much more capable, and with sane mass estimates that costs more but not too much, then that is what should be done. If you go to Congress or NASA execs with a plan that it none of these things and costs $30Bn versus $55Bn for a plan that is, then I don't think you'd be taken seriously. NASA ought to be able to afford an $80Bn mission over ten years with Shuttle/ISS money.

The moral of the story is, that MarsDirect isn't an acceptable plan because it is impractical at any price and because a superior mission arcitecture is available that does not cost too much to afford.

"Actually, designing the mission around the launcher IS the way things have always been done."

Apollo is a terrible example to follow to get to Mars, it was a essentially purely a flags/footprints mission designed to be built in the absolute minimum time possible. Apollo yeilded very low marginal science returns and had no hope of being much more then a minimal Lunar taxi design all for an extreme cost. If we try and make a Mars mission that way, it will be rejected for sure. Without the motivation of winning the hearts and minds of the world over from Communism, then there would have been no Saturn-V and probobly no Apollo.

Again, designing the mission from the launcher up is a mistake. The liklyhood that you will have to cut too many corners in mass, safety, and productivity late in the design phase - where it is too late to make big system changes - in order to make the thing fly at all... particularly with the extremely optimistic MarsDirect arcitecture. Settle on the mission paramters, then design your vehicle, and only then when you have a good idea of the vehicle mass do you make a rocket big enough to launch it.

As far as reactors go, I think that Doc Zubrin is letting his zeal get the better of him yet again. The SP-100 is a fairly big reactor, 2.3 megawatts, and has very low power conversion efficency. The idea that it could be made in a tiny light weight package without a signifigant technological breakthrough is incomprehensable.

The Comet "Saturn-VI" isn't going to happen, restarting Saturn construction would be very expensive, and throwing away 16 large engines on every flight, 32 per mission, would cost a fortune. A launcher based on a mixture of Shuttle and Delta-IV technology is the superior choice, using the enlarged SRBs and shuttle-style tankage plus upgraded Delta main engines and electronics for superior heavy lift for less.

For intents and purposes, Shuttle-Z and Ares are more or less the same thing... A Martian prize is complete nonsense, no company in their right mind of the size needed would risk so many billions with no assurance of any return.

John Creighton · 2004-12-05 11:47:09

"Actually, designing the mission around the launcher IS the way things have always been done."
Apollo is a terrible example to follow to get to Mars, it was a essentially purely a flags/footprints mission designed to be built in the absolute minimum time possible. Apollo yeilded very low marginal science returns and had no hope of being much more then a minimal Lunar taxi design all for an extreme cost.

Of course the worst example of choosing the launcher first is the ISS. Imagine the ISS was built with a HLLV (right acronym?). Then the ISS would be finished long ago and we would have heavy lift today.

GCNRevenger · 2004-12-05 11:53:00

And a word about the science payload... under a ton is probobly not going to be good enough:

-High resolution TOF mass spectrometer(s)
-Electron microscope with a variety of analyzers
-Vacuum pumps for operating both
-Optical microscopes (at least two or three) with acessories
-Drilling rig capable of making multi-meter holes
-Reuseable amino acid chirality detectors (at least 3-4)
-Glove box for shirtsleeve handling of samples w/ small airlock
-Robot rover(s) for general purpose scouting and suspect biological sample gathering, perhaps RTG powerd
-Hammers, chisels, shovels, brushes, CO2 sprayers, scoops, and a variety of sample bags/jars/dishes
-Multiple computers and hardend memory storage devices
-Sufficent MAV/ERV capacity for signifigant sample return, which will cost signifigantly more mass then the samples weigh

...and I'm just getting started

John Creighton · 2004-12-05 11:55:45

Robot rover(s) for general purpose scouting and suspect biological sample gathering, perhaps RTG powerd

The robot rovers could be part of a previous mission.

-Drilling rig capable of making multi-meter holes

Perhaps a robotic drilling rig could also be part of a previous mission.

As for other equipment how about some dynamite for seismic testing.

GCNRevenger · 2004-12-05 12:01:34

Oh, and lets not forget the weather station payload, and a supply of multiple weather balloons with various instruments.

No, no the rover couldn't. The practicality of landing close enough to a pre-landed rover to be useful is slim so it must be carried with you, the rover will have been sitting for a while (too long to assume operation), but also that the rover must be "clean" if you want to use it to pick up samples to minimize risk of Earthly contamination.

I am thinking a rover tucked in with the rest of the science gear and sealed in a plastic box filled with an aniseptic gas, where you would drop it off near the site where you want to go "bug hunting," clean the box, and then stand off while it goes to collect the samples for return to the Hab/Lab with minimum contamination.

The rover may also need to carry a small drill with it too... explosives, good idea. They will weigh quite a few kilos with safety packaging.

John Creighton · 2004-12-05 12:10:05

Oh, and lets not forget the weather station payload, and a supply of multiple weather balloons with various instruments.

Why can’t this mission be done as a precursor robotic mission?

GCNRevenger · 2004-12-05 12:15:17

It doesn't need to, but it would be much easier to deploy and launch the balloons by hand rather then building a robot to do it.

Plus you can have them operate near the landing site where you want to learn as much about the site as possible.

And frankly, the marginal cost of adding them to the manned mission where you can just unpack them is probobly pretty small compared to designing, building, and buying a rocket for a robotic one.

John Creighton · 2004-12-05 12:19:52

As far as the science payload goes we really have to start thinking about what humans can do much better then robots per dollar. Otherwise we might as well just have the people their to test out ISRU based life support techniques. Are they better at setting off explosives then robots? I don’t know. Are they better at scraping samples off the side of a canyon then robots? I don’t know? Can we build a robot that will winch itself over the side of a canyon? People certainly aren’t better at taking pictures then robots so do we really need people to go site seeing to all or mars great geological wonders? Maybe the picture is worth more if a person is in it? Maybe the golf club ads value? How should people work with the robots? Should they drive around looking for interesting places to send the robots? Should the people just stay at the base and the robots bring the samples back? Should the role of the human be primarily one of maintenance?

John Creighton · 2004-12-05 12:21:58

And frankly, the marginal cost of adding them to the manned mission where you can just unpack them is probobly pretty small compared to designing, building, and buying a rocket for a robotic one.

Maybe you are right but these are the things we have to look at. Still before people come there will be precursor robotic missions and these should be planned with as much foresight as possible.

John Creighton · 2004-12-05 12:33:46

One clear purpose of people is to test out ISRU life support techniques. While people are testing out these facilities we should consider the best use of their time. It cost millions to send a robot to mars and as a consequence the travel much slower then they need to for reasons of safety. With people on sight the safety level could be reduced and the robots could operate much faster then usual. A human could be on sight to perform such maintenance tasks as lifting a robot of a rock and replacing their batteries. Or transport them to a new sight much quicker then they could by their own devices. Granted it costs billions to send people but if one person could fix over a hundred robots in their spare time over the course of a mission it could worth while. Granted this task should not take the majority of the peoples time on mars so we should think of other activities that might be important. I for one would like to know how Martian conditions effect child birth. Whether congress would approve such an experiment early on I don’t know. Start with cows and eat the parrent after it delievers.

John Creighton · 2004-12-05 12:42:20

There has been discussion about the increase mass artificial gravity add to the trip in terms of structural support. One advantage of artificial gravity is that convection will naturally circulate the air. The consequence is life support system has to do less work, will last longer and may even be lighter.

John Creighton · 2004-12-05 12:49:14

Plus you can have them operate near the landing site where you want to learn as much about the site as possible.

Isn't weather more of a global phenomenon then a local one? Wouldn't you want the balloons distributed over mars as confined over a small area? Weren’t you the one that wanted to explore the whole planet and not stick to one base.

Dayton3 · 2004-12-05 12:52:45

To me, recovering and reusing launcher equipment used in the Mars Direct architecture makes little sense.

Reuse only makes sense if you have a large sustained launch rate.

An ongoing Mars exploration using Mars Direct would only mean an average of one heavy lift vehicle launched each year.

Even if you had long duration lunar missions based on Mars Direct, that would only add two launches per year.l

I don't think three launches per year justifies recovery and reuse of hardware.

And I"m tired of people putting down Apollo. Apollo was a great program. The basic Apollo Hardware provided 75% of the hardware needed to send a manned mission to Mars even back then not to mention giving us our first space station. And alot of good work was done in Skylab.

Not to mention that the scientific data returned by Apollo exceeded many times over all the data on the moon gathered before or since by unmanned probes.;

GCNRevenger · 2004-12-05 13:15:11

"As far as the science payload goes we really have to start thinking about what humans can do much better then robots per dollar."

If the MERs cost just under a billion dollars, and a manned Mars program will cost around $60Bn, then I think it is very safe bet that the human missions will easily generate sixty times the return.

The intelligence, higher quality senses, the dexterity, the speed (lack of time lag), and so on with humans far exceeds the capacity of robots. A human geologist could have done everything that the MERs did in the matter of a few days. The problem of time lag is also insurmountable. The moral of the story is, that robots can't hold a candle to what humans can do.

"Weren’t you the one that wanted to explore the whole planet and not stick to one base?"

Which is why there will be multiple missions to multiple locations planet-wide. My point is to get as much information from each site as possible, which means monitoring atmospheric conditions & chemistry near the landing site, which can be done with anchored balloons.

"And I"m tired of people putting down Apollo. Apollo was a great program."

You'll get no argument from me on this, the Apollo program fulfilled its mission with spectacular sucess... but just putting a man on Mars and back is not going to fly this time, and this time there aren't any Communists to race.

Apollo in the sense of a mission to study the Moon and for growth options just didn't offer much, and it did not provide "75%" of the hardware needed for a Mars trip. It worked great to get humanity from here to there in the shortest practical time though.

Circulating the air on the spacecraft is not a big energy concern, just some low-power fans.

SpaceNut · 2004-12-06 05:57:00

I sounds like Nasa is dusting off the old viking engines for the next generation lander for 2009.

Aerojet Tests Engine Design For New Mars Rover

Aerojet is building three new 700 pound thrust monopropellant rocket engine assemblies to further evaluate design changes made to increase mission flexibility and life capability. Testing is planned to continue through 2005 to support technology development for JPL.
The most significant feature of the monopropellant engine is its ability to throttle from 15-100 percent thrust with a fixed propellant inlet pressure.

Would a monopropellant be in the cards for the manned lander in the future?

GCNRevenger · 2004-12-06 18:39:02

Nah, you'd want a two-componet fuel for safety. NASA DRM suggests Methane and LOX, which can be kept stored for almost indefinate periods, which would provide high performance and not explode if it leaks.

Mad Grad Student · 2004-12-09 20:56:24

The moral of the story is that MarsDirect isn't an acceptable plan because it is impractical at any price and because a superior mission arcitecture is available that does not cost too much to afford.

I have to respectfully disagree here. Could a superior mission be made than Mars direct with much greater science return per dollar spent? Sure, with a lot of emphesis on the could. In addition to more money, creating big components for the mission from scratch with unproven technolgoy (ie new HLLV, nuclear rockets, more advanced recycling tech) takes time. A lot of time. It only took eight years to go from Freedom 7 to Apollo 11, but NASA was being ripped to shreads as the Apollo astronauts were landing. Had it taken two more years we might never have landed on the Moon. People often forget just how easy it is to delay something fatally, and by waiting on any new expensive technology you're just asking for this to happen.

Zubrin has gone to great lengths to come up with a really good architecture with Mars direct. It might not be the best as far as science value, but it is the most practical and implementalbe plan out there. Mars direct is safe, cheap, and though it might be a little dirty there's still a lot of good science that can be accomplished with it. In general, I think that many of the detractors of Mars direct either don't understand some of the basics about space exploration or are just trying to get attention. It's a very sound system, and I'd be willing to bet that whoever goes to Mars first will do so on some variation of Mars direct.

GCNRevenger · 2004-12-09 21:36:56

"Zubrin has gone to great lengths to come up with a really good architecture with Mars direct."

And in his zeal to see it done, he failed.

"Mars direct is safe, cheap, and... a lot of good science that can be accomplished with it."

It is not nor is it capable of any of these things. The mass margins are everything since the arcitecture is so constrained, and its just not doable, probobly not even with zero science payload allowance. Its like Zubrin was making a bid to NASA like Boeing or Lockheed, but instead of bidding low on the price, he bid low on the mass. True to form, if NASA buys into it, it will be too late to cancel when they figure out it can't be done as planned at all. Or else NASA will do somthing stupid and cut corners again.

"In general, I think that many of the detractors of Mars direct either don't understand some of the basics about space exploration or are just trying to get attention."

Thats a rather.. brazen assumption of you.

You also underestimate the trouble of building Ares versus other HLLV concepts, and probobly underestimate the difficulty and bennefit of building NTR engines again.

GraemeSkinner · 2004-12-09 22:53:07

"In general, I think that many of the detractors of Mars direct either don't understand some of the basics about space exploration or are just trying to get attention."
Thats a rather.. brazen assumption of you.

*Gulp* I'm going to agree with something....

The statement looks far too much like "unless you agree with Dr.Z your wrong" - Thats not a good scientific viewpoint.

Graeme

Mad Grad Student · 2004-12-09 23:11:55

"In general, I think that many of the detractors of Mars direct either don't understand some of the basics about space exploration or are just trying to get attention."
Thats a rather.. brazen assumption of you.

Okay, poor choice of wording perhaps. If you disagree with Dr. Z (as he seems to be called), fine, if you can argue successfully why he's wrong. I haven't seen someone do that satisfactorially yet, but I suppose I could be proven wrong at any time. What I meant was that many people like Jeffry Bell attack Mars direct simply because Zubrin and other advocates of it support it so vigorously. I don't argue for Mars direct unconditionally in any way. A mission architecture should only be supported on the condition that it is good and can stand up to all (or most) opposing arguments. I'm not trying to personally attack anyone here, sorry if it seemed like that.

With 1990 level technology everything in Mars direct was conceptualized with a 10% mass margin. That's somewhat tight but still doable, and considering that that estimate was with 15 year old technolgoy, the mass margins should be easier to achieve now. The science return might be pretty low with pure Mars direct, but it's back at the lab where most of the science will take place anyway. You go to the field to gather samples and study formations in situ, then go back to the lab for the heavy duty analysis, this is the way that science is always done. Since the ERV makes its propellant on Mars it will be able to return substantial amounts of samples to Earth, this is still viable stuff.

Like you said earlier, any sort of humans-to-Mars program (perhaps barring battlestar galactica-type boondoggles) will have a much higher science return per dollar spent than robotic missions. If nothing else, the quick and dirty approach at least has a much higher likelihood of succeeding and is less likely to be cut down by whoever the next president is. Getting to Mars is hard, but convincing governments to go there is even harder. A $20 billion mission will always look more attractive to politicians than one four times the price, even if it has a tenth (I'll be generous) of the science value. The real barriers keeping us from the red planet are the politicians' beliefs that space means nothing and that Veterans' Affairs and other such causes are more important. They're noble for sure, but we all have to make priorities. In this area, Mars direct has a clear advantage over any other proposed mission.

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