New Mars Forums

The quantities of money seem kind of underwhelming, though.  But I suppose we will see.

Quaoar wrote:

Is not simple to extract oil from soy, corn or sunflower seed: you need solvents and a very good system to remove them. Whitout a chemical industry, on Mars is better to use olive oil that can be extracted by pressure only.

That's how it's normally done, but you don't have to do it that way. Use of a solvent gets the most oil, but as you said that creates the problem of removing the solvent. An expeller uses mechanical pressure to extract oil, no solvent. It doen't extract as much oil, but you don't have to remove the solvent.

This manufacturer produces one sized for a kitchen. It's intended for oil seeds: canola, sunflower seed, sesame, safflower, hazelnut, flax (linseed oil), grape seed, and rapeseed (American to copy canola, grows in their climate). However, it can be used for soybeans as well. I emailed the manufacturer. His reply:

It will work for soybeans, although the oil contents is beneath 25%. I managed to press the oil with a handy trick: just before pressing I soak the beans in boiling water for 2 seconds, let the water drip off and press the warm beans. I expect there is a difference in oil contents between soy varieties too. Turning of the crank requires some extra muscles.

http://www.piteba.com/eng/index_eng.html
http://www.piteba.com/images/oil%20expe … _thumb.jpg

The mass discrepancy is far less. For one thing, you need a back up reactor. This is human beings we are talking about - you can't assume 100% operational ability. Either that or you have to take back up solar panel mass.

Also, nuclear reactors are not so good if you want to pursue a sensible policy of pre-landings. You'll need solar for those I would suggest. So why not take a lot of that solar panel mass in bite-size pieces.

Of course once there, you can probably build reflective technology at no or little mass cost. It might be possible to begin that on the first mission.

You don't need a backup nuclear reactor, because the space reactor has no moving parts, and once setup is not really vulnerable to failure short of being hit by a meteorite.  The thing about a nuclear reactor with no moving parts (which is this design) is that once it works on the ground, nothing is really going to change that.  With no cyclic loads, thermal cycling, extensive pre-flight testing, etc etc etc. you can be fully confident that your nuclear reactor will work.  Perhaps a couple hundred kg of batteries would be needed, or more likely a small methlox generator (The engine will probably be about 40 kg, while the generator will probably not be more than 60 kg, for a total of 100 kg.  Say 150 kg for the generator, including all the externalities.

I've also heard of natural gas being used in a fuel cell, which implicitly means that methane could be too.  This would be more efficient and also probably have an even lower mass.  You've been throwing around this "second reactor" argument for quite a while when there is really no reason to think that one would be necessary.

Is a second reactor more safe?  Well, yes.  But so is a second hab.  Do you propose to send two of those?  How about a second dedicated ERV, just in case?  Or perhaps we should send a clone of each crewmember, cryogenically frozen, just in case the original should meet some fate?

My point is that it's not necessary and increases cost while not decreasing the mission risk significantly.

In any case, logic dictates that rather than sending two 80 kW reactors to provide 80 kW, you send two 40 kW reactors; If one should meet with an unexpected failure, you still have half of the amount of energy you need and can spend twice as much time making fuel, which will still result in fuel production being completed before the fuel is actually needed.

Further, cycling the ISRU (In-Situ Resource Utilization) unit as you will have to as part of solar power will result in a higher probability of failure, and necessitates excess capacity on your ISPP (In-Situ Propellant Production) unit, which will be split into several identical subunits so as to be failure-tolerant.

In addition, because a nuclear reactor will mass in the 3-5 tonne range, it's small enough to land by itself.  This is a factor of 3-5 larger than Curiosity, which is a very reasonable scale-up of the technology.  Seeing as the Hab will mass significantly more I don't really see how this is even an issue, either from a technological or safety standpoint.  Keep in mind that in the Mars Direct architecture you do have the option to re-send the entire system on the second launch window should it fail at the first.

Beyond this, that level of manufacturing is rather silly to incorporate in a first mission.  It's a high level of risk for almost no return, just the kind of thing that is worth experimenting with but not depending upon.

It's interesting here that despite the fact that we're proposing systems that are now nearly identical, we're having the same argument we've had on the matter for the last few years

Regardless, I still hold that Nuclear Reactors are technically preferable, but only an issue insofar as the politics get in the way.

NASA complained that Mars Direct was too small. Reducing from 6 crew to 4 will already gain objections. Using ISPP for the entire return to Earth will also gain objections. I did include artificial gravity for both transits: Earth-Mars, and Mars-Earth. Shrinking any further puts mission objectives/value at risk.

But we should move this to the Mars architecture thread.

Decimator wrote:

louis wrote:

1. Procreation will require some extended replication of 1G

What do you base this on?  We have no data between zero and one gee.

Probably 0.38 gee is enough for a correct embryo-fetal development, but as you correctly say, we have no data (if not, it would pose a serious limit on animal breeding)
A one gee facility will be very likely needed for a correct body development of the martian children.

Hi Louis:

First time I'd seen it,  thanks.  Any manned settlement Mars One establishes is going to need a large supply of water (locally as ice).  They need to develop some ground truth about buried glacial deposits of ice at all the sites they are considering.  I've never seen a lander or an orbiter equipped to do that.  Saw nothing in the article about that,  either.

Water content in the Martian soil suffers from two really serious problems:  (1) 1-2% ice-in-soil is an awfully diffuse resource to recover,  and (2) an awful lot of that soil-bound ice seems to be far too salty for human or agricultural use without some sort of chemical cleanup. 

In contrast,  a buried glacier would very likely be real freshwater.  Especially if it once was pack ice from a vanished ocean.

To find out what's really down there,  and how much there really is,  takes a drill rig capable of drilling as much as a kilometer down.  Based on the probe designs I've seen,  we'll not get data like that until men go,  and even then only if their rover has the drill rig on it.  Needs a digging blade,  too.  Basically,  we need a backhoe/front-end loader,  but with a drill rig on it. 

I surely would hate to see people settled onto a site that turns out to be a dry hole.  Because then we'd have to watch them all die without realistic hope of rescue.  Commercial or governmental,  doesn't matter;  there is nothing as expensive as a dead crew.  That's been the history of it,  going back to the first manned flights in the 1960's. 

GW

The MarsDrive roaming mobile plan had cargo lander predispositioned aroung mars as to keep the mass of the RV down if it were to circa navigating of Mars. The same preload plan was also for a localized research radius as well.
The remaining group seems to have gone roage off on there own at this point so marsdrive is sort of stopped in design developement from what I can see.

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.

Oops.  Aluminum wheels may not have been the best choice for a long-life nuke rover.  News stories today indicate unanticipated rates of wear attributed to rough ground. 

Everybody who has ever hiked around in the mountains knows how rough that kind of ground can be.  Not sure whether weight or cost drove them to aluminum wheels,  but I'd bet that team is regretting that choice now.

GW