New Mars Forums

I've always had this thing for the color red

The US's system is far from perfect, and these are just the prices we have to pay to get political support for our space program.  Frankly as pork goes it's not that bad, at least the majority of it is going to support some fairly usefull and basic reasearch.  I'm sure much worse stuff is lurking in the main (non-earmarked) budget which probably full of useless, overpriced, contracts for stuff that will never see practicle development.

If you want my opinion on where to slash budgets the US military and medicare are the #1 and #2 places to start.  Compared to these NASAs budget is minute and it's pork realativly harmless.

I agree with almost everything said here except this.  Orbital corrections are generaly very mild manuvers requiring delta-v's of of a couple hundread of m/s a year at most.    These sorts of manuvers aren't time critical, it's not like the station is going to suddenly crash into the moon if it doesn't do the correction at that very moment.  So a ion-engine could quite easily provide the necessary delta-V (over a period of days or weeks, depending upon its thrust).

Mercury is realy far to close to the sun, to small, and to tidally locked to make surface terraformation a good idea.  But that is not necessarily the only way to go!  It might be very possible to terraform the INSIDE of the planet.  Mecury probably has a solid core, which is likely VERY rich in dense metals (iorn primarily, but with other goodies in their to.  Build a orbital mirror and burn a very deep whole in at one (or both) of the poles.  Then dome the whole with some semi-reflective material to block out what remains of the suns rays.  The whole could potentialy be of extreamly large size because Mercury's gravityis very weak, and because the interior atmosphere could help support it.  Then you would have nice living quarters ready to take advantage of mercuries vast mineral and energy wealth.

Sort of.  A typical magnetic confinement based engine uses a stream of extreamly high velocity quarks (that's what Pions and Kaons are).  Like .9C or better velocities.  These particals quickly decay into more gamma radiation, but they are out of your engine by that time.  While a conventional ion engine is pushed by lower velocity, higher mass ions (atoms striped of electrons).  The faster, lighter particles a anti-matter engine uses gives it a much higher ISP, but the thrust is generaly not signifigant, as the containment equipment is very bulky, and the particals are very light.

Sure you can dilute the anti-matter with other matter, and use it primarily as a heat source, but this results in a few problems.

#1. The heavier particles are obviously going to move slower, which results in a lower ISP, but higher thrust.
#2. Containing the hot-matter becomes an issue.  This limits your propellent velocity to that similar of a NTR.  As magnetic containment is rather impratical, and there is a limit to the heat materials can withstand without melting.  Which limits you to NTR type performance.
#3. It may be the case that the containment device for the anti-matter weighs more than the radioactive source would for the NTR, in which case the thrust to weight ratio would be inferior to the NTR.

To me the most plausible design I have seen for anti-matter engines are those that use anti-matter to catilise a fusion reaction.  This could give you orion like specific impulses or better, but with out so much radiation (though more neutrons).

An idea I've been thinking about involves using positrons.  If we react positrons with hydrogen atoms, annilating the electron, we would get alot of gamma radiation (which would heat the proton involved), and the resulting ion could be magneticaly directed.  Sort of like a ion-engine on anti-matter steroids :-)

I certianly wouldn't rule it out, but you are right it is still a few decades (or more) out.  Anti-matter production and containment methods certianly need more time to mature.  But I've long thought that anti-matter might reach fruitin before fusion ever does.  I can see a clear path for improvment in anti-matter at least, who knows when (or if) fusion will mature.

You couldn't be more wrong about this.  While it is true that an anti-matter engine would have tremendously incredible fuel efficency, or specific impulse, the thrust that they can produce is generaly pathetic.  While it is true that e=mc^2, this does not mean that expelling light is going to give you an incredible change in momentum (which is what thrust relates to).  For a object with 0 mass (like light) the relevenat equation is E=pc (E energy, p momentum, and c is the speed of light).  Which generaly dictates that for most sane energy expedature rates of anti-matter you are going to be looking at very, very, little thrust.  Mainly because there are limits to the amount of anti-matter you can react without blowing your ship up.  The thrust to weight ratios of most pure (ie undilluted) anti-matter drives are pathetic.  Generaly much less so than of the ion-drive which you seem to berate.

Also, you are generaly incorrect in your assumtion that anti-matter engines are driven by photons.  While it is true that there are anti-matter engines that rely upon photons, they are generaly not the most popular in the public conciousness.  They rely upon large blocks of tungsten or some other dense/high melting point substance to absourb the radiation from an anti-matter drive and re-radiate it as lower-energy photons (which can be reflected with mirrors and the like).  While potentialy very efficent, they have perhapce the worse thrust-weight ratios as the tungsten block is very heavy and the rate at which you can react the anti-matter is very slow (because you don't want to melt the block). 

Most proposed anti-matter drives rely upon magnetic containment to re-direct the pions and kaons that an anti-proton proton collision creates for propulsion.  The rest of the energenic radiation (primarily gamma radiation) is far to high energy to be re-directed as a propulsive source, and so is lost.

I don't consider myself a hard-core Zubranite, but the mission plan proposes (Mars Direct), and the refined version adopted by NASA with their DRM is clearly supperior to that which had come before it.  Namely the earlier Mars Plans going as far back to Von Braun and typified by George Bush Sr. so called "90 day report."

The line of reasoning is simple.  For a Mars Mission to be carried out the cost of the mission must be brought down to realistic levels.  The simplest way to do this is to minimise the number of launches necessary, and minimising the total mass of the mission.  This rules out large 1000MT spacecraft.  This is not to say that I do not belive that a Mars Mission could not be carried out in such a manner, simply that it would be extreamly difficult to get it funded, and it would be very wasteful in space of the alternatives.

But the primary reason I (and probably other members of this board) have ignored this post is that it provides little of the concreat details necessary to critique its mission plan.  Without the necessary details, it's little more than a book advertisment, something these boards are realy not the place for.

The cable will have to be tapered anyways.  The problem is if you don't reach 60 GPA the amount of taper you need at the top cannot be large enough to support the bottom.  Remember that mass scales with the cube while strength only scales with the square.

However I'm not sure that these pessimistc observations mean the end.  New methods of creating nano-tubes may be discovered that have lower defect rates.  New methods of creating mass bundles of long nano-tubes need to be developed in anycase.  OR new quality control methods may be developed that can eliminate the defects may be discovered.  OR it may turn out that the rate of defects is low enough that sufficent amount of the nano-tubes strength may be transfered to the bundel at large making the defects irrelevent.  His studies seems to indicate that this will not be the case, but I am sceptical, and would have to read the paper to be convinced.  OTOH, this is not my area of specialty and it evidently is his.

Sorry it took me so long to reply, Real Life (TM) intervens, on the plus side I could be seeing some serious dough if the chemical process I am developing gets purchased.

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The amount of thrust generated by 5 SSME (5x1.8MN=9MN) and 3 RS-68 (3x2.9MN=8.7MN) is comparable, with the SSME actualy being slightly supperior.  So I see no reason why the SSME could not use the large 10m tank.  It's the SRB that provide most of the boost at launch anyways, as both engines (and most liquid fueled engines in general) have problems with gravitational losses.  As for either engine going out of production, I wouldn't worry to much in either case.  The SSME is not currently in large scale production and likely never will be, however Rocketdyne can still assemble new units as needed, and will not likely throw away this valuable capability even if the SSME is "downselected" as for the RS-68, returning them to service would only cost a fraction of their long term cost anyways, so I wouldn't worry about that to much either.

It's harder to make a simple spherical section design self-righing then it is a biconic, as you have less area in which you can put your center of mass, but not impossible.  One way to achive this would be to focus the shield (and center of mass) to one side of the vehicle, so that the engines come down mainly facing on their side relative to the atmosphere.  In any case, the tank can be redesigned to accomidate a larger biconic heat-shield, this may be necessary in any case.  The trailing edges of a biconic heat shield need not be as heavy either as they face less of the heat load.

Again, using the larger tank can more thank make-up for this payload penalty, as could an up-rated secound stage (which we probably want to do eventualy anyways).  Scaling the recovery system will be good practice anyways as we eventualy want to deploy such systems (or very similar systems) on Mars.

But realy, the pod is not that diffrent from the disposable RS-68 design in terms of it's requirments.  It has a heat-shield and a recovery system, but otherwise they are functionaly identical.  It's power system needs to last only marginaly longer, it's avonics and control needs are virtualy the same.  Gimbles and the like are identical.  And with the proper design of it's heat-shield no atitude control is necessary as it will naturaly fall in the proper orientation (and if it DOESN'T naturaly fall in the proper orientation no attitude control system will likely be enough to allow it survive re-entery).

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Without manned space-flight there is no reason for the Kennedy or Johnson Space Centers, at least not at their current levels.  I doubt there is anything the senators/congresspersons from Texas or Florida would take in trade for shutting down these multi-billion dollar parts of their economies.  I just don't share your doubt that manned space-flight is in danger.

Two simple reasons. 
#1.  Historicaly this has been true.  Nasa's budget for space-flight manned and un-manned has been increasing over time in real dollars.
#2.  Nasa is a bureaucracy and the nature of bureaucracy is to expand over time.  This is as inevitable as the expansion of our goverment in general is.  In fact is actualy a subtule plan for budget expansions as an actual moon base and missions to Mars will require more money then is currently budgeted.

I agree with most of your reasoning here, but not with your conclusions.  It's very hard for me to understand people arguing that saving money is a bad thing.  If we want to waste money, we could keep the shuttle going for heavens sake.  Heck an ISS style Moon or Mars mission might be possible if we realy want to.  It's this kind of reasoning that got us stuck in our current rut.  Without continuing efforts to lower the cost of space-travel we will end up doing nothing.

I never argued that we should somehow "save" the extra money in bank someplace, maybe "saved money" is a bad choice of phrase if it leads you to thinking down this path.  What would instead happen is that NASA would have to spend less on the VSE and could spend more (or lobby for more money more succesfully) to spend on other productive endevors.  Ann odd phenomenon that you sometimes see in buisness and goverment is that more money is more happily thrown at ecnomical and sucessful programs then those that are more wasteful.  In any case, the goverment at large rarely wades into an itemised report of spending and so will most likley vote for a yearly NASA raise based upon the acomplishements of the space-program, and nothing else.

As I said before, the pod will likely be recovered over land not see, and so corrosion due to sea-water and a the expense of a recovery fleet are not necessary.

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A side note on the economics in general, think about the long term alternatives to the CaLV for HLLV?

#1. Space Elevator - This would be the best, but it may never be technicaly possible.  The start-up costs and time are bound to be huge even if it is possible (though I would agree that there are worth-while).

#2. Totaly Cheaply Reusable Launch Vehicle - SSTO or TSTO HTHL style - Still incredibly technicaly difficult to impossible.  And even if one of these is made, it is not very likely going to be in the 100MT range.  If we are lucky maybe 20MT or so.  Still leaving a place for the CaLV

#3. Clean Sheet HLLV, totaly or partialy reusable - the only solution we can count on being able to design.  The question is, could we improve upon the CaLV especialy, the CaLV/Pod design?
- The CaLV/Pod already mounts engines at the bleeding edge of performance, reusability, and relability, the SSME.  Unless some dramatic new fuel type is introduced, it is unlikely that a new engine type could be designed that has a drasticaly higher ISP than the SSME combined with being cheaper to reuse and safer.  The only area it could be improved upon is thrust, which really isn't that necessary.
- SRB are pretty cost efficent, but the CaLV could replace these with RS-84 Powered flyback boosters for even more juice and lower cost.
- Fuel Tanks are large and hard to recover no matter what you do.  I have a hard time imagning a re-usable tank that does as much as our current ET, with diffrent staging options you might though
- The EDT is currently totaly no-reusable, so there is room for improvment

Basicaly, when I look at the alternatices, the CaLV with upgrades looks pretty good.  It's hard for me to imagine how we could do better for large 100MT payloads than it in any new design, though I am open to suggestions.

A lot to reply to here, so bear with me.

The RS-68 produces more thrust than the SSME, so you only need three of them to do the same job.  However, the two engines have similar ISP (the SSME is slightly supperior) and thrust to weight ratios (I think the RS-68 is slighlty supperior).  Of course going with 5 SSME gives you an engine out ability an a minor increase in payload (though the engine pod would eat all that up and more).

The recent IIA block of the SSME and new space shuttle main engine processing facility hae brought the costs down signifigantly.  And the incramental costs involved in flying the shuttle have always been pretty low.  If we assue that thing such as the Stenice Space Center and the SSMEPF are going to remain open servicing diffrent bits of our new infastructure (which I do) the additional incramental costs is all we have to pay.  And I got that figure from the simple 1/10 of what it costs the shuttle to do the same thing guestimation :-)

If it can't quite make a full-orbit that it is sub-orbital right?  The key cost saving diffrence here is that if it doesn't achive orbital velocity it wouldn't require a OMS for a circulisation burn.  And if it's heat shield is self righting (which a good capsle style design should be) it wouldn't require a RMS either.  It simply falls back to earth on it's ballistic trajectory, which (if we play are cards right) would bring it back down for a soft touch down somewhere over Texas.  The engine pod can be set on this trajectory before seperation, while the EDS can reconfigure for it's own trajectory during it's insertion and circulisation burns.  As for a power-system, the podless CaLV is going to require this as well, only it has to through this away and doesn't get to recover it.  Or is the entire first stage going to be powered and controled by the (also disposed of) Earth Departure Stage?

This is a good place to note the the pod could share many of the same or similar system as the CEV, such as the semi-reusible heat shield it is supposed to have.  Also, by going for a once-around soft touch down we can eliminate the recovery fleet and share our landing system development with the CEV as well.

No rocket is easy to design, but aside from technical challanges with the heat-shield I see no show stopping reason why it couldn't be designed.  Unlike the shuttles engine compartment it will not have to make room for the Bulky OMS and their fuel.

As I said earlier, the pod can share some of it's heat-shield design with the CEV, which (last I heard) is planed to be semi-reusable.  So the heat-shield would not be expended every mission.

I have no arguments against the comments about it's weight.  It will be heavier then the pod-less design and will diminish the CaLV payload somewhat.  However, switching to the SSME gives a slight increase in performance, which offsets this somewhat.  Switching to the proposed chemical flyback boosters could also help make up the diffrence.

Well the engines themselves were probably the single most expensive item, but that development cost has already been paid for.  Next probably comes the thermal protective system, which the pod can share costs with the CEV with.  Likewise with it's recovery system.  However, unlike the CEV or the orbiter, the pod has to deal with keeping people alive for long periods in space or signifigant orbital manuvers in space.  So if we compare the simpler engine pod to the CEV my 8 Billion dollar estimate is again rather concervative.  As the pod mass at most half as much as the CEV, expecting the program to cost half of the 15 billion alocated to the CEV is not unreasonable.

We have to take a long range view on space vehicle development.  The shuttle has been with us for over 20 years now (longer if we go from the first date of first conception), and we a still looking at using it into the next decade.  I hope the CaLV proves to have as succesfull a career as the Shuttle does.  Or better yet, if we could be more like the Soyuz, that would be even more development.  When we have vehicles that are going to be around for that length of time, it only makes sense to evaluate their costs over that length of time as well.  Also hopefully once we have a 100MT launcher with low-incremental costs to put things into orbit we will start launching them more often.  The CaLV/CLV combo is ideal for building and maintaining a space stations as well as the Mars/Moon missions, and of course the more cargo we put on the Moon/Mars (which wouldn't necessarily require a CLV launch) the better as well.

It's not fair to assume that the RS-68 has no additional design cost associated with it.  The shuttles tank is going to have to be modified to accomidate it, and new power, control, and gimbles systems will likely have to be designed as well.  Certianly the pod would cost more to develop, but the RS-68 isn't free either.

Here we see the benifit of an expendable rocket design program.  We could build the CaLV with the RS-68 now and develop the SSME pod later.  Since the CaLV is all disposable anways, nothing is lost by going with this approach.

Well there are no guarantees in life, much less space travel.  But we have every reason to belive it would be more reliable.  The SSME is already one of (if not THE) most reliable engines in existance.  Going with 5-SSME adds engine out ability to the CaLV, which again increases reliability.  The pod's heat shield also will see extensive testing via the CEV before it is ever launched.