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Also do not forget, that 1MT must also include the fuel tanks for the fuel too. Overall, powered breaking isn't out of the question, but if you are going to do that and bring the fuel you need for the trip back to Earth, forget about chemical rockets. Nuclear rockets on the other hand could pull it off perhaps.
Oh and because of the thin Martian atmosphere, a big heat shield is probably preferred, unless your vehicle has a relatively low density.
And last, Lunar refueling is a bad idea, because it takes about as much fuel to get to the Moon then just to go to Mars directly.
The larger faring also permits NASA to use a shorter but chubbier EDS stage, which in turn lets the first stage core get longer without making the rocket any taller, so it carries more fuel for more payload.
This is the first I've heard of the drop-tank idea after Lunar orbit insertion being seriously considered. Sounds like a good idea to me.
Gaetano, this is a discussion message board to get informed, propose, and debate various topics about spaceflight. Because there are many different topics, the board is divided up into many threads, but if you post lots of stuff into a thread that isn't related to that topic then you are personally disrupting the necessary organizational structure of this board. Also, starting large numbers of new threads for every little idea about a particular vehicle you come up with competes for screen space with other threads that are more focused on a wider variety of topics. Hence, you damage the ability of the board to function coherently and fulfill its purpose. This is why you have been asked, reasonably I might add, to keep your new ideas and discussion thereof about the particular vehicles of the Constellation project confined to a single thread.
Second, I think you have obviously and repeatedly used dishonest discussion tactics and an actively annoying typing style for self-gratification at our expense. You take credit for things that are objectively simple, you place your judgment on par or even above professional aerospace engineers, and you do not take one second of time to make your posts unobtrusive or inefficiently use screen space, unless you are prodded to do so. This shows that you are inconsiderate of others on the board, and are here to show off your ideas and receive praise for them, and not to inform nor discuss nor debate anything in good faith.
This is not about majorities rule or your "rights:" your posts use up space on our board without honestly contributing to what the board is about. Unsolicited posts, advertising something for the benefit of someone else at our expense, particularly in an annoying style of writing... what does that sound like? SPAM! Heck, you've even burned about 100 lines of screen space in the past dozen posts for less words than half of this one.
Something else, you seem to suggest various ways to "improve" designs but you give no evidence if your suggestions are feasible.
For example, in your "How to design a lighter orion" you talk of cutting bits and repshaping the capsule, but you do not give considerations why its already ike that (those things include aerodinamics, material strenght and weight, and inernal architecture to provide overall intergrity), plus you go around making assumptions on the aerodinamics of re-entry for various capsules, and a complete lack of numbers (including the calculations) and if you do provide numbers you dont provide support for them.
Something else too, your web pages text style feel as if it where screaming right at you, Oh and VeryEasyEuro is a terrible url name ad if i were you i would have droped the very (although the whole name feels like a con-website, i wonder how many people have contacted you about buying it).
Oh but he does have numbers for how much lighter or how much more payload his designs have, which is very difficult to calculate accurately without NASA-grade professional modeling. But in gaetano land, his numbers are for us to disprove, not for him to validate. Then he starts with "oh but you don't know I'm wrong" nonsense, where he equates his abilities versus an army of aerospace engineers.
Heh, and that nobody has purchased his insanely over-priced domain name kinda answers that last question, doesn't it?
...money or just recognition...
if it's so "simple" why haven't they proposed two years ago (when I've sent my mail to Google) or (best) months or years before?.
Oh brother
Gaining a little altitude again makes little difference, since orbital flight is all about speed, speed, and more speed. Almost immediately after launch, most rockets flatten their ascent until it is almost horizontal in order to gain speed. Altitude is just to get out of the drag of the atmosphere, but in a cyclone the air is still quite thick.
Assuming you could get controlled ascent in one, which I highly doubt.
As far as a spacecraft riding an ion beam to orbit, again not really practical. Ion beams don't work very well in the atmosphere, since the air actually blocks/scatters/deflects ion beams pretty efficiently. Furthermore, like the problem with laser ascent, they are inefficient and you can't track the beam on the vehicle for long since it will simply go over the horizon. An ion beam also penetrates more than a laser, making it more difficult to protect a vehicle from the beam, and may actually pose a radiation hazard.
The point of contention is that NASA's five-segment first stage with small upper stage somehow has a vibration issue but the four-segment first stage/large upper stage will not because Shuttle doesn't have the problem.
This is not true, because the problem in Ares-I in either configuration is due to the much larger thrust from the SRB paired with the much lower weight of the upper stage versus Shuttle. So, simply because the four-segment booster does not have a problem with Shuttle does not mean Ares-I with the booster will not.
The problem in either version of the Ares-I should be pretty easily fixed.
It will not. No proposed version of the Ares-I upper stage will be radically heavier than the current one, and even with a modest decrease in thrust of the four-segment booster, you will still have vibration problems to contend with. The Shuttle external tank, fueled, weighs almost eight hundred tonnes, and add the Shuttle orbiter with a full payload to that, and the boosters push almost a thousand tonnes. Ares-I's upper stage doesn't weigh anywhere near that.
Gaetano, chanting things in upper case, particularly things that aren't true, is very bad form. The kind of thing spammers and children do.
I agree with everything Ciclops says:
-The present Orion is the right size (seats 4 for a week, or 6 for a few days). Its perfect for what NASA needs it to do.
-The four-segment booster cannot be used on Ares-I without much of the same modifications that the five-segment booster will need. Adding a segment to a booster is really not very hard, and most of the expense for the five-segment booster involves other things like improved thrust vectoring that Shuttle doesn't need. It is just a simple, plain, and obvious lie to say that the booster is "readily available now."
-Remember that the vibration issue is a fluctuation in acceleration not thrust, it isn't a problem for Shuttle since it is much heavier the acceleration is lower. The same percentage changes to the lower acceleration yield less vibration on the heavier Shuttle. For that matter, since your designs are generally lighter, the vibration problem will be a problem for you too. Gee, I hope it might be possible to fix it, heh.
Got any more caps-lock lies to pollute our board with, gaetano?
I am all for compressed air for indoor use, its just not a good idea for the surface of Mars.
Oh brother... I don't even know where to begin.
I vote for E) as well
Gaetanomarono circa >1000BC: Hey, early man, putting the animal in the front of the cart (instead of the side) was my idea!!!
Gaetanomarono circa 1900AD: Hey Wright Brothers, putting a propeller on a flying wing was my idea!!!
Gaetanomarono circa 1930's: Hey Robart Goddard, putting the second stage on TOP of the first was MY IDEA!!!11!1
Gaetano, one of the reasons that nobody respects you is that you take credit for simple or obvious ideas, and loudly insist that you be given praise for it or defend them with intellectually dishonest prattle. Thus, spam.
Given the LAS motors size/weight and the Orion's SM design have to be attached to the capsule either on the top or on the sides. If a flipped coin lands heads up instead of tails, why should we give you any credit?
Even then, your drawing of LAS motors on the bottom of the capsule is not what NASA is considering with the MLAS system, despite what you insist. Further dishonesty.
And last but not least, big advertisements for ghostnasa T-shirts and a banner ad for "VeryEasyEuro" domain name that you are selling for thirty thousand euros. Not merely taking credit for a simple, obvious bit of marketing but actually charging a huge sum of money for it. Spammer.
Well hold on a minute,
That Hyperion reactor is an interesting idea, but its pretty far from a flight-weight reactor. Even with a VASIMR engine and gobs of energy, if the thing is too heavy you still won't get anywhere. The has got to weigh only tens of tonnes, which includes everything. I am sure that a space version of the power plant with turbines, radiators, power conditioners etc will weigh an order of magnitude too much at least.
Anyway, speaking of a reactor of similar output and temperature as Hyperion, that 27MWe advertised comes at the expense of a heavy water-cooled steam turbine system... but I digress, this cooling system removes essentially all the heat from the reactor, and in the process the hot steam loses a great deal of energy and this "luke warm" steam is what carries the 70MWt of waste heat from the reactor.
This steam could be piped through a nano-thermoelectric system perhaps, but it would not have anywhere near 45% since it is not very hot anymore. Long story short, you don't have that 70MWt of thermal energy available to you at high temperature if you use the Hyperion's steam turbine system.
The mass of the cooling loop, turbines, generators, radiators, power electronics, and structure for all this are going to put you waaay over mass budget.
If the cable failed, nothing really bad would happen, you'd just lose your artificial gravity and need to make a minor course correction.
As far as mid-course burns, do we really need to do those until the vehicle nears its destination? The last week or two of the trip could be spent zero-G without much trouble.
And as far as orienting a communications antenna or a solar flare shield, its possible to use the RCS systems to control which direction the axis of rotation points, either at Earth for communications or the Sun for solar flare shielding. Complicated yes, but not overly so.
Tether-driven artificial gravity is a realistic option, it trades a major human health concern(s) that is/are hard to fix for technical ones that are much easier to deal with.
It is true that it won't work for DRM-5 very well, but it would work for the older DRM-3.
Concentrated Hydrogen Peroxide is already running up against the limits of whats safe enough to handle, scary stuff like cyclic Tetraoxygen I wouldn't even handle a thimble full in the lab much less a hundred tonnes.
The fact of the matter (no pun intended) is that we're running up against the limits of the energies contained in practical rocket fuels.
A tether-for-gravity system really isn't that complicated, and would be a pretty easy addition to a Mars vehicle design. The EDS stage will probably already have thrusters, just increase their fuel tankage a little and add power/control/telemetry links to them via the tether cable. A simple shape charge or explosive bolt cutting mechanism... It really won't cost that much.
In fact, such a system doesn't even need space testing short of the Mars ship I bet, the cable doesn't care if you are pulling on it in space or on the ground in a vacuum chamber, its all the same to it. Hit it with heat/radiation/derbies in said chamber to test it if you really have to.
Anyway, thats a good thought from Robert that equipment won't have to be zero-G rated if the ship isn't going to be in zero-G for any length of time, however in the event of trouble I think the vehicle should be able to operate sans-gravity and should be tested likewise.
The main troubles with a tether system are that you can't use it after you cut the EDS stage loose, which unfortunately you have to do in order to aerobrake, and it you can't readily dock with a spinning vehicle (eg docking with lander).
It would also complicate rocket braking maneuvers dramatically, to the point where you would probably want to cut the EDS loose before such a burn.
So, spinning works great for MarsDirect or DRM-3, but not so good for DRM-5, since the former two fly directly from Earth to Mars atmospheric entry, and the return vehicles don't spin until after the crew has boarded. In DRM-5, the same vehicle is used for the outbound and inbound leg of the trip, so the ship has to slow to Mars orbit, exchange crew with the lander at least once, and then return to Earth.
Yeah that does sound awfully good to be true, 50% efficiency?
The latter link you provided had a 25% efficiency if I read it correctly, which is pretty darn good... the catch is its only good for 6mo and only at lowish temperatures thats going to make the radiator system awfully heavy. You also need a very effective radiator to hit low enough temperatures.
Its a good start though
Edit: I am a little worried that such a device might not stand up to intense radiation all that well however.
This is not a great idea either, a compressor is a fairly inefficient machine so while the RTG's electrical output would increase, a lot of power would have to be syphoned off to run the compressor...
...but the real biggie is safety: the compressor would have to run all the time, because if it failed, then all the CO2 would boil/sublime in the tank, causing it to over-pressure and explode! Unless of course you dumped the CO2 overboard, in which case the RTG would overheat since it is wrapped inside a CO2 tank that would trap its thermal output.
Not enough energy produced per kilogram to be useful, plus no practical way to store them other than in solution and they would be extremely corrosive. Likely also some problems with the salts clogging the engine.
I'm disappointed that the idea of mars cars powered by compressed CO2 is so quickly dismissed. Powering cars with a compressed version of the local atmosphere would be a simple and elegant method of propulsion; if it could be made to work. Is there anyone here that could look into the physics a little further?
Well, the problem is pretty insurmountable: CO2 will turn to either a solid or liquid at any appreciable pressure, and such cryogens are useless to push vehicles with on the cold surface of Mars. So unless you have a huge gas tank for the stuff, you won't be able to carry enough to go very far.
For a stationary application, again, you are going to store solar power in a battery/heat sink to boil carbon dioxide to turn a turbine to turn a generator? Why not just store the solar energy directly in a battery/heat sink and use it directly, skipping the boiling CO2 bit.
Ehhh I'm not sure I buy the argument, which seems to be based on some pretty complicated but back-of-the-envelope modeling for gravitational losses, acceleration, and so on. Specifically, he may have a flawed assumption of constant Isp vs air pressure for a Peroxide/Kerosene engine.
I kinda doubt that Lockheed/Boeing just sort of overlooked this option after decades of cryogenic rocket building.
I'm not sure I would classify near-100% peroxide as being "safe" to handle either.
I doubt they wanted to harvest the gas during ascent to power the rocket, since even with the high bond energy released the tiny amount of the gas present would mean near-zero thrust.
And no, simply because it is monoatomic it need not carry a charge, and in fact if it did have a charge then the stuff would not recombine from 2N to N2.
These kinds of metastable fuels are not actually difficult to make, the bond can be broken by zapping them with the appropriate sort of energy, the trouble is storing the stuff such that it won't recombine until you want it to in the engine. Nitrogen here has the same problem as Hydrogen, in that there is no way to bottle the stuff in any useful quantity.
Thermoelectrics don't have the needed efficiency; for instance the SNAP-100 reactor that the USAF was working on actually put out 2MWt of heat energy, but the poor conversion efficiency of the thermoelectric converters it used (5%, 5W of electricity from 100W heat) limited its electrical output to only 100kWe. Even a doubling of this to 10% would not yield enough power from a reactor of practical mass to run VASIMR.
The core in the Hyperion reactor uses Uranium Hyride btw, which i any case won't get hot enough, and Thorium Hydride on its own can't undergo fission. And, while NERVA could operate at very high temperatures, the core literally melted/ablated at these temperatures and were not suitable for long-duration use at those power levels.
What we need is something like this: http://www.inspi.ufl.edu/gcr.pdf ...the cost of which would bankrupt NASA within the next 10-20 years, if they had to develop this along with a massive VASIMR engine.
Ehhh, VentureStar was pushing the practical mass envelope even if it did work as advertised, meaning the thing would have been bloody expensive and finicky like Shuttle probably.
And besides, we don't really need lots of light-to-medium lift right now, heavy lift is what we need to get to Mars.
Finally with the launch market as bad as it is these days, such a vehicle would probably be a commercial failure.
Not so fast,
The trouble with this reactor is two fold: first off, how do you get the energy out of the core and convert it to electricity? In the Hyperion concept, this is with a heavy steam turbine and low-temperature radiator/condenser. Getting such a contraption on a space vehicle is going to be extremely heavy.
Second, the core operates at a fairly low temperature, which will make cooling systems big and heavy as well.
Making a dozen-megawatt reactor light enough is easy, cooling the reactor is the hard part.