New Mars Forums

As the others have said the lowest semi-stable orbit you can have is someplace ~350km above the Earth.  This isn't completely stable as atmospheric interference will slowly degrade this orbit in about 5 years or so.  So any vehicle in such an orbit must be periodically re-boosted or it will come crashing down.

Its really not possible or economic to have a station at an altitude much lower than this, as atmospheric interference rises drastically and it will come crashing down much sooner.  In any case getting into orbit is more a matter of velocity, not altitude so putting you station lower (in a slightly slower orbit) really doesn't help you all that much.

As for all the variance in figures in the ISS's orbit thats because like any object in such a low orbit it's altitude is not completely stable and varies as it is reboosted periodically.

I hate to start of with an 'appeal to authority' argument, but it seems the most logical one to start with.  The engineers at NASA are fairly smart guys.  They have managed to design quite a few successful spacecraft so far.  So it seems to me that they would notice such glaring design discrepancies like the Ares I not having enough thrust to lift itself of the ground.

Indeed the image you post clearly shows that the vehicles Gross Lift Of Weight (GLOW) is considerably less then the thrust of the first stage.  Why on Earth would NASA fabricate these documents if it were not so?

Clearly the most likely solution to this dilemma is that your calculations showing that the 5 Segment SRB is not powerful enough are in error someplace.

I guess that supposes what you want the oxygen for.  If you want oxygen for smallish scale uses (like providing oxygen for the crew, or for fueling a rocket) then the best solution is probably to crack water into H2 and 02.  Mars has fairly large quantities of water, and if your station has access to it, that is probably the best choice.  Failing that you can either liquefy the thin martin Atmosphere and extract some oxygen from that, though this would be more energy intensive.  As a bonus you would be able to extract other useful gasses like Nitrogen and Argon.  Or you could crack the C02 in the atmosphere for Oxygen as well, but this is also fairly energy intensive.

If you are talking about a very large scale (like terraforming Mars) then your options are much more limited.  Water you obviously want to keep for other uses in your ecosystem, and liquifing the atmosphere obviously will not work.  Your only realistic option is to sequester the carbon out of the CO2 getting you oxygen.  On Earth this is done by planets (research the carbon cycle) who use photosynthesis.  This is not quite so easily done on Mars as likely no terrestrial plant can survive in the current martian conditions.  So any carbon sequestration efforts will likely be made as a part of a whole package of terraforming efforts.

First Mars needs to be heated someway.  Popular options are decreasing the albedo, or amount of light Mars reflects by dusting its polar caps with soot or black lichen.  Or you could put a giant mirror in orbit.  Digging giant bore holes to the planets center has even been discussed.  Greenhouse gases might also be used.  As the planet heats up, the CO2 on the poles will be released, and the atmospheric pressure will be increased.  This would both further increase the temperature (CO2 is a greenhouse gas as well) and allow more complex plant life to be distributed.  Industrial efforts to sequester carbon on a large scale might also be used.  It would also probably be necessary to import large quantities of Nitrogen from Titan or Venus, and possibly some extra water as well.  Hopefully at some point the heating and carbon removal operations will result in a livable enviroment.  But that would likely be decades if not centuries after the process has started.

IIRC the process is actualy exo-thermic (ie releases its own heat).  It happens quite readily at room temperature, but you would have to consult a chemical table or do some experiments to get a better read out on how temperature effects it.

I guess it depends on what you mean by optimal.  On Earth human civilization has reached the point that the environment in which you live generally does not have a significant impact on your life expectancy.  Or rather other effects such as quality of health care in the region, common genetics in population groups, and culture influences on lifestyle completely mask any such effects.  Life expectancies in most developed nations are vary similar.

That said, we should expect life at different pressures and especially gravities to have significant effects on human health.  One might expect life at a lower gravity to produce a lesser strain on the heart, and thus lead to lower incidence of heart attacks (the #1 killer in developed countries IIRC).  On the other hand lower gravity might lead to a less powerful and more atrophied heart, which might counteract these effects.  It might also lead to a increased  numbers of overweight and obese people, which would also counteract any benefits.

Higher gravity would probably lead to an increased rate of injury due to accidents.  At G's not much higher then 1.5 or so even walking or sitting an lead to injury.  Of course lower G's might lead to a loss in bone density, which would could also result in increased injuries.  Especially in aging women.

All in all these effects are hard to determine in advance.  The human body is quite adaptable, but to truly get a good idea of what living conditions are "optimal" you would have to do some long term studies on largish population groups.  I do think the health effects of life at different G's could be significant, though I wouldn't wager a guess as to in which way.

One thing is fairly certain is that minor variations in the atmosphere we breath are not likely to have insignificant health effects.  We have lots of good data for people living in long periods of times in different atmosphere's and there doesn't appear to be any long-term significant effects.  Life at lower partial pressures of O2 leads to more red-blood cells, which might makes you "healthier" but doesn't necessarily mean you live longer.  Likewise, higher pressure atmospheres develop stronger lung muscles (diaphragm) but this doesn't necessarily correlate with increased life span either.

As you apparently know the melting and boiling points of ice/water is dependent on the pressure it is under.  So if you lower the pressure the water is under, the temperature it boils/subliminates at will decrease as well.  So if you evacuate the atmosphere in a room containing alot of ice, you could possibly expect more of it to turn into vapor.  However, if you decrease the pressure in the chamber by evacuating a portion of it (ie, removing the air, while keeping the volume constent) the temperature will also decrease, causing it to freeze again.  In the end you will end up with relatively little water vapor and ice, as water exists in a fairly narrow temperature band and ice freezes readily.

But actually that is irrelevant to this discussion, as no matter the process you arrive at it at, you must in the end deal with an environment that is survivable by humans.  That means something close to 1 atm and 32*C.  At these temperatures and pressures the properties of water are fairly constrained.  Only a tiny fraction of it can exist as water vapor (about 35 mm HG) and the rest must be plain water.  If you started at different conditions the mix will reach equilibrium as you try (but fail) to bring it to human surviable mixtures.

Your right that this is better in some ways then a simple rocket, but it is not without issues. 

Firstly the issue of inefficiency and dispensing with the massive amounts of waste heat generate by GW and TW scale power sources.  Dealing with it at the plant may not be an issue, but the space-craft still has to dispense with the waste heat generated by any inefficiencies at its end.

Secondly obviously there is the issue of building such large power plants.  Be they lasers, partical beams, or rails guns.  To give you an idea of the scale, all of Human civilization currently consumes like 2 TW or so right now.  So building these things is a huge effort.

Lastly (and most importantly) focusing these beams of interstellar distances is difficult to impossible.  As the spacecraft speeds away it gets harder and harder to keep the beam on it.  Worse, diffraction and to a lesser extent diffusion (for particle beams) also limit the distance you can beam power.  It's really not possible to beam power out past a few tens of AU.  This limits the distance in which you can accelerate, and unless you are willing to accept absurd G forces, you can't get going all that fast (maybe .3C) in that time.

Well unless you are going considerably faster then .5c most Nebula are far out of range.  The nearest the helix nebula is some ~500ly away.  Of course any trip to the stars is probably going to take at least 50 years or so, but the nearest nebula are some ways away.  And you are right that a nebula could be dangerous.  Heck anything is dangerous whey you are traveling at a fraction of light speed, even interstellar dust.  Which, incidentally, provides another method of slowing down.  Magnetic braking against the interstellar dust.  The problem with this is the dust is (thankfully) very thin, so it takes a long time to slow down this way.  Which will increase your trip time.  Alternatively some sort of rocket may have to be employed to stop.

Are you talking about trying to use a rail gun to accelerate the ship?  This is entirely impractical.  The length of a rail gun strong enough to accelerate a vessel to .9c (or even much smaller fractions) is impractically large.  And if you are constrained to human survivable G forces, then it just gets worse.  Recall that at 1G acceleration you would get out to pluto in about a week but even at that point while you are certainly trucking, you haven't even reached .1c yet (more like .01c).

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I also think interstellar travel will almost certianly be one-way.  The distances and time involved are FAR to great for it to be anything else.  Not to mention the colossal expenditure of energy/production.  I'm also dubious that people, as we understand them today, will ever travel to the stars.  Any ship providing for human comforts would be massively larger and the trip time (probably longer than 40 years at least) is prohibative on the human lifespan.  This requires either hybernation or generation ships, which are even more stupidly huge.

Most likely to me is the seeding of some-sort of von-neuman probe.  And possibly by the time we the capability to do that it will be possible to digitise and transmit the human conconiousness and transmit that.  That the only way I think we will ever travel to the stars... BUT it would be at the speed of light

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In any case my favorite method of interstellar travel is remarkably simple.  Drop a very large mirror (500km+) very close to the sun (.1AU or closer, as close as you can get without burning it).  Counterbalance this mirrors mass and reflected energy with the suns gravity to keep it stable.  Then focus its beam on a lightweight sail pulling your spacecraft.  If your sail is light enough you could achieve extreme acceleration this way, like greater then 9Gs.  Not much good out past Earth, but you are going way fast by that time anyways.

Well I wasn't necessarily talking about anti-matter.  Either some sort of fusion drive or possibly even a gas core nuclear reactor could have the ISP necessary for 1G acceleration for short trips like to Mars or Jupiter.  Most fusion torch drives have ISP up around a million, but if you crank their thrust up to 1G it generally drops.

In terms of Serious long term application of 1G applications of thrust I was speaking of total conversion of mass to energy.  IE some magical method of instantly converting matter into energy with 100% efficiency.  Anti-matter comes close to this, but is generally not 100% efficient, as some of its energy is almost always unharnessed (the best designs being maybe 60% efficient).  But even with such an engine (the best theoretical possible) you really can't sustain such high levels of thrust for very long.

See for a 100% efficient photon drive (ie total conversion) the mass ratio of craft is equal to e^(a*t).  My calculator seems to be broken right now, but just eyeballing it I can tell you that even for short periods of time the mass ratios are still huge.

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As for speed vs payload, there may be payloads where this tradeoff makes sense.  However you could carry litteraly millions of times more stuff if you went slower, which seems to indicate to me that for a great deal of time-insensitive cargo going slow seems more logical.

Your correct that the term originates from WWII, where it was used in a variety of offensive slogans and gained its offensive connotation.  Like this darling little comic.  I know quite a few Japanese people, and all of them find the term offensive.

But don't take my word for it.  Websters, Oxfords, Wikipedia, Wiktionary, Farlex Free Dictionary, and other I'm sure all agree.

And while I don't personally find the term "Yank" offensive, living in the Southern as I do, I know MANY people to whom those would be "fightin' words."

#1.  The term "jap" is generally considered a racial slur.  Similar to, but worse than the term "nip," (short for Nipponese)  I'm sure you didn't mean it as such, but most Japanese find it offensive.  As do I.

#2.  Not that I advocate selling our transferring our rocket technology to the Russians, but they could manage quite well with out it.  I mean they built the Energia without our help, and it is in many ways a superior design to the Ares V we are currently considering.  I also bet that Russia could pay for such a vehicle if they wished to.  The economy of there is slowly stabilizing and turning around, they simply don't wish to spend the money that way at the current time (better things to spend it on).

#3.  I'm a big fan of the Japanese, I think many Americans underestimate that country.  However, they are not supermen and their country is not without its faults.  It's space program in particular has not produced especially spectacular results, its primary launch vehicle (the H-2) is both expensive and rather untrustworthy.  In the end they are a country in many ways similar to the US.  And their space program is vulnerable to graft, incompetence, and cost overruns just as America's is.  They put their pants on one leg at time, just like us.

Now I have no doubt that the Japanese COULD produce an Ares V, or any other sort of HLLV if they wanted to.  The questions is, if we want to get to Mars fast is having them build it the best way to go?  I think probably not.  They have no experience in building vehicles of this size, they are still struggling with ones in the Delta-IV range.  Even if we simply trucked over shuttle technology to them wholesale (a plan Boeing and Rocketydne among others might have a small problem with).  They still probably wouldn't be up to speed with the US.  They lack the necessary infrastructure to assemble and launch such a large spacecraft for one thing.

Sure it would be cheaper for the US if we had them build it for us (ie we didn't have to pay a thing).  But in terms of absolute cost it would undoubtedly cost the Japanese more to do it then it would NASA.  I'm not sure why the Japanese would agree to such an arrangement.  And if they did, they would certainly be the Senior partners in it, not the US.

Now I wouldn't have any objects to your proposal if it went the other way around.  If you were proposing say to have the Japanese design and build the Ares I while we focused on the Ares V I would be all for it.  The Japanese could also probably produce and excellent rover for a Mars mission as well.  I even think co-opting the JAXA for our moon and mars mission is an EXCELLENT idea.

The problem with using Fluorine as a oxidiser is it is highly toxic.  While a H-F combustion reaction gives you a slightly higher ISP then H-O reaction, the difficulties in handeling Fluorine are conciderable.  Flourine is the most electronegative and reactive of all the elements.  In its pure elemental state it will burn with practicaly anything, including water and most metals, and is virtualy impossible to extinguish.  As noted before it is both toxic and corrosive, and frankly an all around nasty stuff to handle in large quantities.  Furthermore it is relativly expensive, much more so then liquid oxygen certianly.  And even after it is burned it produces hydrofluoric acid, which is also nasty, toxic, and corrosive.  Sometimes small quantites of Lithium are also proposed as an aditive to H-F rockets for even greater ISPs, but again toxicity is a problem.

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As for Ammonium Nitrate, it's not unknown as a rocket fuel.  It's performance is similar to that of and Ammonium Perchlorate which is more commenly used (such as in the shuttles SRBs).   I belive Ammonium Perchlorate is perfered generaly for its longer burning times and slightly higher performance, but the two come pretty close.  Both are obviously considerably inferior to H-O rockets, or even Kerosene/Ox, but supperior in terms of thrust.

I really don't have anything to say to this accept that you are completely incorrect.  Gravity is not generated by motion, it is an intrinsic property of mass.  The dispersal of dye in a swimming pool is governed by Brownian motion and perhapses centrifugal force if the water is being rotated.  Gravity has very little to do with it.

Try this test instead.  Drop a 10 pound and a 18 pound bolling ball at the same time from the same height.  They will both hit the ground at the same time.  Then perform this same expirment in a car/bus/plane or anything else you might expect to generate "gravity" I think you will find that the rate of fall will be exactly the same.

On the contrary Einstein's laws are quite well tested, both on Earth and in Space.  Every time someone uses a GPS device they are reliant upon correction made to the device due to special relativity (SR).  You are right that these laws may not have been tested in far of universes or the void of cosmic space.  However the observations we make from these locations are consistent with SR and one of the Axioms of science is that the laws we discover are universal, even in locations we cannot test/observe.  As these locations are (by there nature and definition) unobservable/untestable we have to accept that one on faith.

What is this babbling?  You can't "attach" a gas atom to the orbital of another gas atom, atom can't simply swap in for electrons, even if they were somehow inert (they aren't).  Nor can you attach an atom to a photon, and even if you could this wouldn't allow you to accelerate the atom to light-speed.

Remember the iron claw laws of thermodynamics.  Energy into the system must equal energy out of the system.  You can't get something for nothing.  So in order to accelerate a ship to near light speed you must expend enough energy to get it there, there are no fancy tricks around this.

A NEO mission would be a great shakedown mission for testing the long duration life-support capabilities of the ITV/Hab or ERV ala DRM III.  Especially since if the ITV/Hab had to do a free-return abort it would be in space for a similar or longer period of time.

Important as well would be to get some indepth analysis of the composition of an asteroid.  This could make later attempts to deflect one if necessary much more successful.