Problems with Mars Direct?

Gregori · 2013-09-30 09:11:15

The Design Reference Missions that NASA has been doing increasingly are moving away from Mars Direct architecture. What are the problems with this architecture that have not been addressed?

For example, How does one land a 50+ tons lander on Mars when we have problems landing more than 1 ton, the heaviest being curiosity and that required an exotic solution? How does food last 3 years without going bad? How do they deal with poisonous perchlorates in the Martian soil?

RobertDyck · 2013-09-30 12:48:39

Don't fall into the trap of believing propaganda.

Curiosity could have easily landed using a lander with legs that have shock absorbers, a platform and a ramp. This lander could have used rocket engines just like Viking or Phoenix. However, all that adds mass. They chose to land on wheels so they could remove the weight of legs, platform, and ramp. And they could have attached the landing rockets to the rover, but they have to be a certain distance above ground or rocket exhaust will dig a hole. With legs, that's not a problem. But landing the rover on it's wheels would have required attaching the landing system to the top of the rover, just to keep rocket exhaust sufficiently above ground. Then there's the question how to get the rover out from under the landing platform, and how to ensure that platform doesn't crush the rover. So their attempt to minimize mass resulted in the sky crane. They had to keep launch mass down to fit on the launch vehicle they chose. They could have landed Curiosity with the system I described, but it would have required a much larger launch vehicle.

Mars Direct includes a habitat that does not have wheels. One design feature will be to keep rocket exhaust away from the ground. That may require placing landing rocket engines inside the lower story, or attached to the side. Simply placing engines below the floor of the lower story would again place rocket exhaust too close to the ground, causing it to dig a hole when it's trying to land. By the way, the Apollo Lunar Module (LM) did have the rocket engine embedded within the lower story. And that lower story was nothing but engine, fuel tanks, landing legs with shock absorbers, and storage compartments on the sides.

As for food: this is where I have to call "propaganda". Someone just wants to justify funding for their study. There is lots of food here on Earth stored for more than 3 years. Here are a couple websites, find more with Google.
http://www.wilderness-survival.net/food-storage-charts/
http://grandpappy.info/hshelff.htm

Perchlorate: Oxygen candles are an emergency oxygen source on the space station. It's a cylinder containing sodium chlorate and iron powder. It reacts at high temperature to produce sodium chloride (salt), and iron oxide (rust), releasing oxygen. Sodium chlorate is a perchlorate, so it's used already. Removing any contaminant from a spacesuit requires cleaning. This is one reason some engineers argue for a mechanical counterpressure spacesuit: it's machine washable.

The only weakness with Mars Direct is the return vehicle. While the hab provides artificial gravity on the trip to Mars, the return has none. The return capsule would be about the size of Dragon. In fact, if you were to design Mars Direct today, you would use a Dragon capsule. But that means 6 months in zero gravity, and not enough room for exercise equipment used on the station. Shannon Lucent spent 6 months on Mir, and walked around the Shuttle upon landing, but she exercise every day. The question is how to do that in a capsule.

RGClark · 2013-10-01 07:13:48

Another surprising fact is that the NASA DRM's do not contain artificial gravity.

Bob Clark

GW Johnson · 2013-10-02 09:05:29

I find it disturbing that NASA still thinks it can send people into a 2.5+ year mission without at least some artificial gravity. Besides the zero-gee transits, each of which is near the demonstrated max exposure time, there is no data at all (of any reliability) to suggest that 0.38 gee for that 1+ year on the surface of Mars is "enough". If bed rest studies were so good, then our bones would soften and decalcify in bed down here the way they do in space. They don't.

You do not have to build giant Battle Star Galactica's no one could afford, or resort to Rube Goldberg cable-connected contraptions of questionable safety at best, to provide artificial gravity by spin. It is easily integrated into a practical vehicle design, even at one full gee, which requires 56 m radius at the tolerable 4 rpm spin rate.

You shape your vehicle of docked modules as a baton that spins end-over-end, with the habitat at one end. This is an inherently stable configuration, as anyone who has ever seen the baton twirlers at a football game can testify. It integrates well with staged-off empty tanks: your baton just gets slimmer. There's no need for a truss, just connect the tanks axially and laterally.

I really have to question why otherwise-intriguing mission designs (of all types and from many sources) so often continue to ignore this medically-devastating issue, yet an issue so easily resolved.

GW

Last edited by GW Johnson (2013-10-02 09:06:54)

Quaoar · 2013-12-16 08:48:33

GW Johnson wrote:

You shape your vehicle of docked modules as a baton that spins end-over-end, with the habitat at one end. This is an inherently stable configuration, as anyone who has ever seen the baton twirlers at a football game can testify. It integrates well with staged-off empty tanks: your baton just gets slimmer. There's no need for a truss, just connect the tanks axially and laterally.
GW

It is possible to sobstitute the rigid baton with an enflatable Bigelow like long boom, that may be stored in the MTV nose during the launch, and can be connected to the bourned stage after the transfer orbital inserction?

Last edited by Quaoar (2013-12-16 08:51:31)

GW Johnson · 2013-12-16 09:46:11

I think an inflatable module for a crew habitat is fine. You do need a rigid structure to take the spin-up /spin-down loads with exciting a bunch of unwanted vibrations. If this structure is your propellant tankage, that fills the bill very nicely. I rather doubt an inflatable boom would e rigid enough for this. To reach 1 full gee, you need a radius of 56 m from center-of-mass, at about the max credible 4 rpm.

GW

Quaoar · 2013-12-17 15:58:13

GW Johnson wrote:

I find it disturbing that NASA still thinks it can send people into a 2.5+ year mission without at least some artificial gravity. Besides the zero-gee transits, each of which is near the demonstrated max exposure time, there is no data at all (of any reliability) to suggest that 0.38 gee for that 1+ year on the surface of Mars is "enough". If bed rest studies were so good, then our bones would soften and decalcify in bed down here the way they do in space. They don't.
You do not have to build giant Battle Star Galactica's no one could afford, or resort to Rube Goldberg cable-connected contraptions of questionable safety at best, to provide artificial gravity by spin. It is easily integrated into a practical vehicle design, even at one full gee, which requires 56 m radius at the tolerable 4 rpm spin rate. GW

As a physician, I also agree that in 4-8 month space travel, a spaceship must have some form of artificial gravity. The gee load during the atmospheric entry may be from 5 to 10 gee: too much for a deconditioned crew. On Mars the astronauts cannot go to a rehabilitation clinic to get physiotherapy: they must be in perfect physical condition to explore an alien world. Mulscolar hypotrophy and bone loss are not the only problems in microgravity: there are also the fluid shift that can cause sight loss for ocular deformation and optic nerve damage, anemy many other cardiovascular, ormonal and methabolic alterations. An alternative to spinning or tumbling the whole ship may be the short arm centrifuge, but we still have not reliable data on this kind of device.
On Mars, during the EVA, an astronaut with a spacesuit has almost the same weight on the Earth in normal clothes, so walking in spacesuit may give a good muscolar and bone load. To counteract the fluid shift caused to the Mars lower gravity, a promising strategy may be to give some 5°-20° of inclination to the beds where the astronauts will slip, with the feet in a lower position than the head.

GW Johnson wrote:

You shape your vehicle of docked modules as a baton that spins end-over-end, with the habitat at one end. This is an inherently stable configuration, as anyone who has ever seen the baton twirlers at a football game can testify. It integrates well with staged-off empty tanks: your baton just gets slimmer. There's no need for a truss, just connect the tanks axially and laterally.
I really have to question why otherwise-intriguing mission designs (of all types and from many sources) so often continue to ignore this medically-devastating issue, yet an issue so easily resolved.
GW

Are you speaking about tumbling some kind of modular space ship like Grant Bonin's ship of Mars for Less?
If so, this may be very good for the MTV. But the ERV have to relay on the classical cable beetween the capsule and the bourned stage or on internal short arm centrifugue.

Last edited by Quaoar (2013-12-17 16:29:11)

GW Johnson · 2013-12-17 19:55:51

Hi Quaoar:

What I had in mind was a ship composed of docked-together modules, most of them propellant modules. The ship will be lighter on the return, and will need fewer propellant modules than it did outbound, but it will still need a lot of propellant. By stacking them up properly, one should still get a baton on the order of 150 m long.

Go see the mission plan I just posted over at http://exrocketman.blogspot.com a couple of days ago. Fig 19 shows a sketch of what I had in mind. Bear in mind that my design proposal recovers and reuses the manned vehicle in Earth orbit at the end of the mission. It's not a one-shot free return design.

Isn't Quaoar the name of a dwarf planet discovered recently in the Kuiper belt? It sounds familiar.

GW

RGClark · 2013-12-19 11:23:43

GW Johnson wrote:

Hi Quaoar:
What I had in mind was a ship composed of docked-together modules, most of them propellant modules. The ship will be lighter on the return, and will need fewer propellant modules than it did outbound, but it will still need a lot of propellant. By stacking them up properly, one should still get a baton on the order of 150 m long.
Go see the mission plan I just posted over at http://exrocketman.blogspot.com a couple of days ago. Fig 19 shows a sketch of what I had in mind. Bear in mind that my design proposal recovers and reuses the manned vehicle in Earth orbit at the end of the mission. It's not a one-shot free return design.
Isn't Quaoar the name of a dwarf planet discovered recently in the Kuiper belt? It sounds familiar.
GW

I like the idea of not relying on ISRU for first manned mission, which means carrying all the propellant from Earth. But about the propellant modules it looks like in your drawings such as Figs. 15,18, and 19 that you are keeping the expended modules. Wouldn't you get a better mass fraction by dispensing with them? This would be analogous to Phil Bono's proposed orbital launchers from the 60's:

Encyclopedia Astronautica.
Rombus.

Rombus SSTO
Rombus SSTO Launch Vehicle
Credit: © Mark Wade
http://www.astronautix.com/lvs/rombus.htm

ICARUS/Ithacus.
Posted on December 2, 2013 by admin

http://www.aerospaceprojectsreview.com/blog/?p=1435

In fact, Bono wanted to use these with orbital refueling for lunar and Mars missions:

Encyclopedia Astronautica.
Project Selena
http://www.astronautix.com/craft/proelena.htm

Encyclopedia Astronautica
Project Deimos
http://www.astronautix.com/craft/proeimos.htm

Also, what are the mass fractions of the propellant modules in your design?

Bob Clark

Last edited by RGClark (2013-12-19 11:29:03)

Quaoar · 2013-12-19 11:34:56

GW Johnson wrote:

Hi Quaoar:
What I had in mind was a ship composed of docked-together modules, most of them propellant modules. The ship will be lighter on the return, and will need fewer propellant modules than it did outbound, but it will still need a lot of propellant. By stacking them up properly, one should still get a baton on the order of 150 m long.
Go see the mission plan I just posted over at http://exrocketman.blogspot.com a couple of days ago. Fig 19 shows a sketch of what I had in mind. Bear in mind that my design proposal recovers and reuses the manned vehicle in Earth orbit at the end of the mission. It's not a one-shot free return design.
Isn't Quaoar the name of a dwarf planet discovered recently in the Kuiper belt? It sounds familiar.
GW

Hi, your ship is very interesting.
Yes, Quaoar is the dwarf planet discovered by Chad Trujillo, who named it after a Tongva native american god, who create the world singing and dancing.

Last edited by Quaoar (2013-12-19 11:37:57)

GW Johnson · 2013-12-19 18:56:07

For the vehicles in my proposal, I did the departure and arrival burns without staging-off any empty tanks. The only staging is leaving empties in orbit at Mars, and returning home on propellant tanks dead-headed to Mars. This two-burn approach increases the number of required modules, yes, but it also allows you to recover and reuse every single scrap of hardware. These propellant modules I assumed to be 5% hardware and 95% propellants.

GW

Tom Kalbfus · 2013-12-20 07:29:56

What exactly is the problem with making methane from carbon-dioxide and water?

GW Johnson · 2013-12-20 10:48:31

"What exactly is the problem with making methane from carbon-dioxide and water?"

Technically - not a lot. Although, it is a very long and expensive way from a desktop scientific demonstration device to something that makes mass quantities reliably in the (very hostile) field.

Ethically - betting lives on gear that you simply don't have a lot of experience with, is a real problem. Why not take both the propellants and the propellant-maker on that first trip? If it works, you get to fly to more places. If not, you still get home.

GW

Last edited by GW Johnson (2013-12-20 10:50:48)

RobertDyck · 2013-12-20 13:39:22

No one has been to Mars before. No matter what you will bet lives on gear you have no experience with.

GW Johnson · 2013-12-21 11:18:51

My point isn't either-or, it's how-much.

We have lots of experience with rocket engines and manned rocket vehicles, dating back to at least the ME-163 in WW2, and a whole lot more with the X-planes at Edwards AFB in the late 1940's through the late 1960's.

We have a lot of experience with capsules and heat shields, dating back to the original Mercury and Vostok flights in the early 1960's, and the warhead entry vehicles before them in the 1950's.

We have lots of experiences with landers and rovers (and landing legs) dating back to Surveyor 3 in 1963, and all the Apollo landings, plus all the Mars landers since.

The combinations of these things that will work at Mars for a manned landing is unique, but at least all the tinkertoys from which the Mars landers will be made have long histories behind them. It's that history that gives you some confidence for betting lives.

That unique combination for the Mars lander is something for which I do not see any ongoing development. That disturbs me, but there is still time to get that done. I do not see any of the space agencies anywhere addressing this, though.

The transit vehicle will have to be designed around keeping a crew healthy and sane for a roughly 2.5 year round trip. I see only some of those things being addressed by any of the space agencies. That disturbs me very greatly. There is so much to do, and not so very much time.

In both cases, the strategic decision-making is lacking, that function being usurped by politics-of-money.

The one item we have been discussing here with little-to-no history behind it (so far) is propellant manufacture on Mars. That is why it is risky: no history behind it. Zubrin's bench-top lab device is not a proper prototype for something we could test, nor are the other similar devices. We need to build and test those prototypes. Now. Yet, no space agency anywhere is doing more than academic lab stuff. That kind of thing just doesn't qualify as an engineering prototype test.

So far, based on the activities underway, I see no space agency anywhere that really intends to send men to Mars. None of the things that must happen are happening.

On the commercial side, there are a very few visionaries willing to take part. Spacex is one, but they have some tinkertoys to offer, not a whole picture, at least not yet.

The other private initiative is that Tito fly-by with a married couple. That's 500 days in zero-gee without radiation protection to shame the government agencies into actually doing something. Almost, but not quite certainly, it's a suicide mission. If the radiation doesn't kill them, the free-entry gee loads will, after 500 days of the effects of zero-gee disease accumulates.

Personally, I like the idea of ISPP. But, it needs some real engineering prototyping and test history before we bet lives on it. If we don't have that history, then you take it along and test it for sure, but you don't bet lives on it, you send the return propellant. If you have an engineering prototype test history behind it, then you can bet lives on it. Basic ethics.

GW

Last edited by GW Johnson (2013-12-21 11:24:30)

RobertDyck · 2013-12-21 12:25:01

Yes, we need that. But it's been 24 years since Dr. Zubrin and Dr. Baker came up with it for Mars Direct. That's plenty of time. It's long overdue, and every year it isn't done is yet more time wasted.

Congress isn't going to spend $450 billion for the 90-Day Report. In another post I pointed out if you deduct $100 billion for ISS and adjust for inflation from 1989, today we're talking about $750 billion. Could that be adjusted down further for technology development, work on SLS, and infrastructure by New Space? Perhaps. We're still talking at least $500 billion / half a trillion! That just isn't going to happen. But the Old Space companies continue to demand a mission to the Moon, permanent lunar base, mines on the Moon, fuel depot in Earth orbit filled with lunar fuel, and all the other stuff from the 90-Day Report. The space station called for in teh 90-Day Report has been built. Old Space continues to push for absolutely everything from the 90-Day Report. Congress keeps claiming that any attempt to send humans to Mars will result in the full 90-Day Report and it's full price tag. They aren't going to pay that. Continuing to push for that only causes an impasse.

Last edited by RobertDyck (2013-12-21 16:38:53)

Quaoar · 2013-12-21 16:19:49

GW Johnson wrote:

The one item we have been discussing here with little-to-no history behind it (so far) is propellant manufacture on Mars. That is why it is risky: no history behind it. Zubrin's bench-top lab device is not a proper prototype for something we could test, nor are the other similar devices. We need to build and test those prototypes. Now. Yet, no space agency anywhere is doing more than academic lab stuff. That kind of thing just doesn't qualify as an engineering prototype test.
GW

Sabatier reaction is very well known and it's used by chemical industry for more than a century. I think it will be not difficoult to build a bigger device and test it in the Mars atmosphere simulator of German Space Agency. The bigger problem may be the energy to run the pump and drive the water electrolysis: small 100 KW nuclear reactor vs. film solar panel carpet. The first may get a lot of political trouble, the second may be very difficoult to deploy automatically: a solution may be and ADEPT like deployable aeroshell-landing gear, with the filmsy solar panels on the internal side of the deployable heat shield, that will be exposed to the sun after landing.

http://www.lpi.usra.edu/vexag/Nov2012/p … cinski.pdf

The real problem is the absence of interest.

GW Johnson · 2013-12-21 18:53:12

Quaoar:

You just made my point.

Of course the sabatier reaction is well known science. Of course it has been used Earthside for a long time. None of that is machinery we can use on Mars. It was designed for Earthly conditions.

My point is that the actual machinery necessary to make it work on Mars has never been designed at all, much less prototyped and tested. That includes the power supply and whatever gas compression machinery they finally select (not at all a trivial problem with an inlet density 0.6% of that here). All those missing support items are part of my point.

I'm not saying at all that it cannot be done, because it so very clearly can. And I hope it is, and soon.

But, I am saying that the necessary things to make it work reliably on Mars are not underway at all. It has to work very reliably at Martian conditions before you ask astronauts to bet their lives on it. Proving that your specific design actually works reliably takes time, effort, and money. It's called "engineering development" work.

There is a vast difference between a lab device that demonstrates feasibility, and an engineering prototype that verifies this thing will really work reliably. It's called engineering development, and not many scientists understand its nature, or how big an effort it really is. They were not trained in it. That's what engineers are trained to do, which is why there are two distinct titles: scientist and engineer.

Typical development, properly done, is at least one order of magnitude more effort, time, and expense, as any scientific feasibility demo imaginable. Sometimes 2 or 3 orders of magnitude. But really talented engineering teams can do it for about 1 order of magnitude.

You don't really find talented, efficient teams like that employed by the "big space" firms. Those guys usually cost you the 2 or 3 orders of magnitude.

GW

JoshNH4H · 2013-12-21 23:14:16

^To be fair, it took Zubrin $50,000 to do a lab demo of the system. Three orders of magnitude more than that is still pretty affordable in the context of a space mission.

louis · 2013-12-22 17:38:23

Quaoar wrote:

GW Johnson wrote:
The one item we have been discussing here with little-to-no history behind it (so far) is propellant manufacture on Mars. That is why it is risky: no history behind it. Zubrin's bench-top lab device is not a proper prototype for something we could test, nor are the other similar devices. We need to build and test those prototypes. Now. Yet, no space agency anywhere is doing more than academic lab stuff. That kind of thing just doesn't qualify as an engineering prototype test.
GW
Sabatier reaction is very well known and it's used by chemical industry for more than a century. I think it will be not difficoult to build a bigger device and test it in the Mars atmosphere simulator of German Space Agency. The bigger problem may be the energy to run the pump and drive the water electrolysis: small 100 KW nuclear reactor vs. film solar panel carpet. The first may get a lot of political trouble, the second may be very difficoult to deploy automatically: a solution may be and ADEPT like deployable aeroshell-landing gear, with the filmsy solar panels on the internal side of the deployable heat shield, that will be exposed to the sun after landing.
http://www.lpi.usra.edu/vexag/Nov2012/p … cinski.pdf
The real problem is the absence of interest.

I don't foresee deployment of PV panels as a problem. Another point - if you have pre-landings the fuel production could be run over several years, reducing the power requirement, I would have thought i.e. if you thought the fuel production would take a year, were we to run that over 8 years, we might need only 12-15 Kws equivalent of PV panel.

JoshNH4H · 2013-12-22 18:17:17

And thus require eight years of lead time?

louis · 2013-12-22 19:53:23

JoshNH4H wrote:

And thus require eight years of lead time?

Yes, but that lead in time could start within a couple of years since we already have that capability - of sending small probes to Mars.

JoshNH4H · 2013-12-22 19:58:11

Yes, but I doubt that anyone would be comfortable sending hardware to the surface before we were really set on what we were using it for.

Quaoar · 2013-12-23 09:43:36

GW Johnson wrote:

Quaoar:
You just made my point.
Of course the sabatier reaction is well known science. Of course it has been used Earthside for a long time. None of that is machinery we can use on Mars. It was designed for Earthly conditions.
My point is that the actual machinery necessary to make it work on Mars has never been designed at all, much less prototyped and tested. That includes the power supply and whatever gas compression machinery they finally select (not at all a trivial problem with an inlet density 0.6% of that here). All those missing support items are part of my point.
I'm not saying at all that it cannot be done, because it so very clearly can. And I hope it is, and soon.
But, I am saying that the necessary things to make it work reliably on Mars are not underway at all. It has to work very reliably at Martian conditions before you ask astronauts to bet their lives on it. Proving that your specific design actually works reliably takes time, effort, and money. It's called "engineering development" work.
There is a vast difference between a lab device that demonstrates feasibility, and an engineering prototype that verifies this thing will really work reliably. It's called engineering development, and not many scientists understand its nature, or how big an effort it really is. They were not trained in it. That's what engineers are trained to do, which is why there are two distinct titles: scientist and engineer.
Typical development, properly done, is at least one order of magnitude more effort, time, and expense, as any scientific feasibility demo imaginable. Sometimes 2 or 3 orders of magnitude. But really talented engineering teams can do it for about 1 order of magnitude.
You don't really find talented, efficient teams like that employed by the "big space" firms. Those guys usually cost you the 2 or 3 orders of magnitude.
GW

You are right, but your arguments may be applied to the whoole mission: we have a lot of expirence in entry and landing, but we never lended on Mars something heavier than Curiosity. A landing habitat of 15-20 mT has also to be designed, prototiped and tested. Even the rover may be an issue: for a more than a year mission, astronauts need a long range pressurizzed rover with a powerfull internal combustion engine, but we never built a LOX-LCH4 internal combustion engine, able to work in Mars climate and thin atmosphere, where cooling may be very difficoult.

I'm not an expert, but I think R/S to develop mission hardware will take almost 10 year and a lot of money, but no space agency has planned such an investment.

Last edited by Quaoar (2013-12-23 09:45:24)

Quaoar · 2013-12-23 10:21:42

louis wrote:

I don't foresee deployment of PV panels as a problem. Another point - if you have pre-landings the fuel production could be run over several years, reducing the power requirement, I would have thought i.e. if you thought the fuel production would take a year, were we to run that over 8 years, we might need only 12-15 Kws equivalent of PV panel.

How long can you store LOX-LCH4 on Mars equatorial latitude?

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Problems with Mars Direct?

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