Phobos First!

[thereiwas]

You can make it as heavy as you want. How fast it works depends on how much energy you have available, and what is in the water. Pure water splits very slowly. Having a bit of salt or acid in the water makes the process go faster. The amount of electricity required is rather large in any case, and sunlight is pretty puny at the orbit of Mars, multiplied by the inefficiency of solar cells. So you need nuclear power. So it is going to weigh a bit. Also, heat speeds up the process.

 

[keermalec]

According to this source, a fission reactor produces about 140 W/kg.<br /><br />According to this source, the solar concentrator arrays used in deep Space 1 produce 90 W/kg at Earth orbit, ie 39 W/kg at Mars orbit.<br /><br />However, the fission reactor described masses 35 tons. For smaller masses solar concentrator arrays seem to be the only viable option. Small scale Radio Isotope Thermal Generators only produce about 9 W/kg.<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[thereiwas]

Say 4.3 kw-hrs per kg of water converted, by one reference I checked, assuming STP. That is around twice what a typical home needs in a day. The process needs lots of amps at around 2 volts.

 

[scottb50]

Then you use bigger arrays. The amount of time needed to breakdown the water can also be planned for and the need to cryogenically store Hydrogen and Oxygen, as opposed to keeping them as gasses can be kept to a minimum. <div class="Discussion_UserSignature"> </div>

 

[mithridates]

For added value to an impactor mission, put a certain amount of black soot-type substance into the impactor that gets spread around after the impact to reduce the albedo, technically making that our first attempt at terraforming a planet. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[mithridates]

Er...for a Mars impactor mission, that is. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[keermalec]

You mean cover the whole planet surface, all 144,000,000 sq km of it? <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[mithridates]

No, I was just thinking of the symbolic value. It would technically be history's first instance of deliberate terraforming. <div class="Discussion_UserSignature"> <p>----- </p><p>http://mithridates.blogspot.com</p> </div>

 

[dragon04]

In no way as a taxpayer would I be in support of any mission to Mars that did not include boots on the Martian Surface.<br /><br />I'd fight any such mission tooth and nail. <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[j05h]

<i>> In no way as a taxpayer would I be in support of any mission to Mars that did not include boots on the Martian Surface.<br />I'd fight any such mission tooth and nail.</i><br /><br />What if the orbit-early approach allowed a Mars landing 10 years before any other scenario, but required the first crew to spend it's time setting up shop on Phobos? This could be considered as the "base camping" approach. Build an outpost or storage cache at every reasonable stopping point. Also, starting by building a Phobos/Deimos station/mine/cache doesn't preclude the same crew from landing on Mars later in their 5-year mission.<br /><br />What about if the Phobos First mission was private? <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[spacester]

<font color="yellow">I'd fight any such mission tooth and nail.</font><br /><br />Your way or no way at all, eh?<br /><br />Very nice. <img src="/images/icons/rolleyes.gif" /><br /> <div class="Discussion_UserSignature"> </div>

 

[keermalec]

Dragon, in case u didn't know, the first two Apollo missions simply went round the moon without setting boots on it. They were necessary for validating the technology which would later on allow us to land.<br /><br />Lucky no-one fought this design tooth and nail or the very first landing may very well have been a catastrophe, or may not have taken place at all. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[spacester]

Looks like Dragon will pledge to 'fight tooth and nail' over future proposals but cannot be bothered to stick around in this thread and defend his provocative position.<br /><br />I don't hang around free space much, but I distinctly recall Dragon very recently chiding crazyeddie for running away in a thread. Not that Dragon bothered to look at the pattern of posting first; he would have discovered that the gentleman doesn't post on weekends much.<br /><br />I just looked at Dragon's posts. I see 33 posts in Free Space since my reply above. None of which have anything to do with space flight from what I can tell.<br /><br />With friends like Dragon, space flight needs not look far for enemies. <img src="/images/icons/tongue.gif" /> He just pops in with a cheap shot every once on a while, I guess. At least when I do it, it is in support of ideas, not just against that which doesn't tickle my fancy.<br /><br />Yeah whatever, Dragon, you tried to convince me once that you are not anti-spaceflight. I didn't believe you then and I sure don't believe you now. Why do you post here, anyway?<br /><br />What does the term 'Flags And Footprints' mean to you, Dragon? For most of us here, it contains a lesson learned.<br /><br />Boots on the Martian Surface is your criteria for Progress?<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[scottb50]

I think we should go to Mars itself first and establishing facilities on Phobos for that eventuality would not be worth the time and effort. Once on Mars and with support facilities in Mars orbit I would be all in favor of exploring Phobos. <br /><br />The gravity on a body the size of Phobos would present unique problems, while Mars would allow pretty much normal human activity. Phobos would be a wonderful training ground for asteroid exploration, since that is what it is to begin with, it seems rather a stretch to think we need to find resources and transfer them to the Planet when they exist on Mars to begin with. <br /><br />I think the best method is having a basic Station in Mars orbit, put in place by the first mission, subsequent missions would dock to it and transfer people and cargo to and from the surface of Mars. When not manned it could be operated remotely from the surface and could be used as an assembly point for asteroid or deep Space missions with crews either coming in from Earth or up from Mars. It would be simple to then explore both of Mars moons and continue outward from there.<br /><br />I see Phobos as another step, we can't go to Mars until we go back to the moon, even though going back to the moon doesn't really have to be done to go to Mars, no we have to go to the Earths moon then Mars moon before we can go to Mars! We've been to the moon and a number of robotic missions make it clear we could exist on Mars, our moon doesn't offer any better location to assemble vehicles then LEO does and getting resources from the moon in a reasonable period of time is absurd to begin with.<br /><br />We could go to Mars today if we wanted to, we could have gone 20 years ago, if we had wanted to. Why not just go? Back to the moon, on to Phobos and finally to Mars pushes the costs to at least ten times what it would cost to simply go to Mars.<br /><br />Maybe we just don't want to go to Mars to begin with?<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[keermalec]

I believe it is all a question of delta-v, which equates to useful payload mass, which equates to cost.<br /><br />Some numbers, from LEO to...<br /><br />The Moon: 6.4 km/s there, 6.4 km/s back<br />Mars: 4.6 km/s there, 6.9 km/s back<br />Phobos: 4.7 km/s there, 2.4 km/s back<br /><br />Using local ressources allows significant cost savings by inducing less payload launched from Earth. Phobos is the cheapest fuel stop in the solar system: it makes sense to take advantage of it in order to reduce the cost, or increase the amplitude, of a Mars mission.<br /><br />If propellant exists on Phobos, I am therefore in favor of a Phobos first approach. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[comga]

In reply to:<br /><br /> I don't see any reason for large LH2 tanks or long term storage of Hydrogen or Oxygen as liquids. Water is a pretty benign way to keep both, either as a liquid or solid as ice.<br /><br /><br />No, Scottb50 and Keermelec, water is NOT a good way to store the fuel, any more than CO2 and water are good fuels for natural gas powered cars. H2 and O2 are ways to store energy, and water is the byproduct of expending that energy. Yes, you could carry water to Mars, but the energy requirements are huge, and the storage issues would be the same after the energy was generated and stored.<br /><br />Zubrin covered all of this over a decade ago in "The Case for Mars". He also addressed the inadequacies of discussing fuels in terms of Isp. Isp is defined as pounds force, times seconds, divided by pounds mass. Zubrin's point was that the key element is pounds *FROM EARTH*. Therefore, if you take hydrogen from Earth, with a long term source of significant power, in his plan a nuclear reactor, you can make twelve times the mass at Mars by harvesting CO2 from the atmosphere. That gives an Isp(launched) of ~420 for LH2/LOX and ~4000 for CH4/LOX produced from Martian CO2 and "imported" H2. Plus you get Methane, which is MUCH easier to liquefy and store than Hydrogen, and requires much smaller fuel tanks on the launch vehicle.<br /><br />The very low density of LH2 is a prime issue, as is its low heat of enthalpy, the amount of energy it takes to boil it. Arguments and calculations that posit equivalences between alternate propulsion systems is not valid unless you make the goal equivalent, that is, payload back to Mars orbit or Earth return trajectory. Then you compare them based on how much mass on the Mars or Phobos surface it takes. <br /><br />However, the basis of this thread is that Phobos or Demios "landings" can allow a relatively low delta-V mission to an interesting target, with or without in-situ fuel production. If there are resources ther

 

[keermalec]

Comga, I agree with everything u say. Concerning the issue of storing "fuel" as water instead of LOX and LH2, this was only discussed and is only valid for transporting Phobos/Mars-mined water back to Earth. We are talking here about water as cargo: it will not be used to propel the craft that carries it.<br /><br />The electrolysis to convert water to propellant will be carried out at destination, in LEO, rather than before the trip, for two reasons:<br /><br />1. more solar energy is availlable in LEO than in LMO<br />2. transporting water is easier than transporting LOX and LH2 (higher overall density = smaller tanks, and higher boillling point = less energy expended in temperature control). <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[gunsandrockets]

<No, Scottb50 and Keermelec, water is NOT a good way to store the fuel,...><br /><br />This topic has been beaten to death before, see this thread...<br /><br />http://uplink.space.com/showthreaded.php?Cat=&Board=businesstech&Number=710778&page=0&view=collapsed&sb=5&o=0<br /><br />Or as Spacester and Jon Clarke put it...<br /><br />Spacester, "I'm going to put this a gently as I can. I like Scott a lot, but he still doesn't understand that you can't make propellant out of water as fast as he supposes. It takes a LOT of energy and power, and both are important constraints on real-world hardware." <br /><br />Jon Clarke, "Yep, just about everyone has this discussion with Scott sooner or later, without much success." <br /><br />

 

[scottb50]

Spacester, "I'm going to put this a gently as I can. I like Scott a lot, but he still doesn't understand that you can't make propellant out of water as fast as he supposes. It takes a LOT of energy and power, and both are important constraints on real-world hardware."<br /><br />Jon Clarke, "Yep, just about everyone has this discussion with Scott sooner or later, without much success." />>><br /><br />Without much success because I'm not talking about hydrolyzing water as you need the propellant. I'm saying that during the transit from Earth to Mars there is a lot of time to produce Hydrogen and Oxygen and in Mars orbit there is considerable time to build up supplies for a return burn and time enroute to Earth to build up supplies for entering LEO.<br /><br />Cryogenics could be used as part of the fueling system with Hydrogen and Oxygen stored as pressurized gasses until large amounts in a short time are needed.<br /><br />I would think a couple of acres of solar panels tethered to the vehicle could provide more then enough electricity for hydrolysis. <br /><br />I would also use fuel cells to provide consumable power for two reasons. The power can be kept better regulated and by alternating cells the heat from the fuel cells can be absorbed by the hydrolysers, allowing higher efficiency. It would be a simple matter to stack alternating cells just like done with fuel cells to increase output.<br /><br />It's not that I don't understand their concerns, it's that I take them into account and think they can be dealt with. Primarily the biggest driving force is the Universal availability of water to begin with and the abundance we have on Earth to get started. Water seems to be the only constant so it seems logical to look to it as a way into Space. <br /> <div class="Discussion_UserSignature"> </div>

 

[gunsandrockets]

The thread I linked to already says everything I have to say on this topic, and I don't feel the need to repeat myself.

 

[comga]

Roger. Thanks for the link. Way too much talking.<br />I am out, too. <br />

 

[keermalec]

Interesting conversation on the previous thread which somehow I had missed before.<br /><br />Just to make things clear: the only use I find in transporting water is when it is mined on Mars/Phobos/Deimos and transported to LEO as cargo. It is not to be used as propellant during the trip.<br /><br />I imagine a solar-powered hydrolysing facility in LEO for converting that water to propellant for selling in LEO.<br /> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[Swampcat]

<font color="yellow">"I imagine a solar-powered hydrolysing facility in LEO for converting that water to propellant for selling in LEO."</font><br /><br />Pardon me for saying it this way, Keermalec, but that sounds like a wacky idea <img src="/images/icons/smile.gif" />. How could mining water on Mars/Phobos/Deimos, then transporting it to LEO and processing it into propellant be better than just lifting it from Earth?<br /><br /> <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[thereiwas]

Is the dV from Phobos to LEO considerably less than Earth to LEO?

 

[nuaetius]

<blockquote><font class="small">In reply to:</font><hr /><p>Is the dV from Phobos to LEO considerably less than Earth to LEO? <p><hr /></p></p></blockquote><br /><br />6 times less<br /><br />From To Delta-V <br />LEO Phobos, Deimos 5.6 <br />LEO Mars Surface 4.8 <br />LEO L4, L5 3.9 <br />LEO Lunar surface 6.2 <br />LEO GEO 4.0 <br />LEO Asteroids 1982 DB 4.5 <br />LEO 1982XB, HR, Anteros 5.3 <br />Mars LMO 4.4 <br />LMO Phobos 0.54 <br />LMO Deimos 0.87 <br />LMO Mars 0.05 <br />LMO Escape 1.43 <br />LMO Earth return 3.4 <br />Phobos LMO/Mars 0.56 <br />Phobos Deimos 0.74 <br />Phobos escape 0.89 <br />Phobos Earth return 2.88 <br />Phobos & Deimos LEO 1.8 <br />Deimos LMO/Mars 0.67 <br />Deimos Phobos 0.74 <br />Deimos escape 0.56 <br />Deimos Lunar Surface 2.55 <br />Lunar surface LEO 3.2 <br />GEO synch. LEO 4.2 <br />GEO synch. 1982 DB 0.14 <br />Earth surface LEO 12 <br />Earth surface GEO 15 <br />