Author Topic: Energy for Space flight.  (Read 7884 times)

Offline ptolemy1977

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Energy for Space flight.
« on: 04/13/2012 12:16 am »
I am new to this forum, I had an idea that I would like to share regarding the use of the vasimr in deep space exploration.  It is clear that the hold up in its use will be providing a sufficiently large power source for this device.  I was thinking about the convergence of several technologies which might address the problem.  1) the bloom box, or fuel cell. 2) bussard ramscoop 3) inflatable storage mediums 4) chemistry.

The problem with deep space travel is the need to go fast and far this requires a lot of fuel or a high density energy source.  Nuclear has often been kicked around as the possible solution to energy density problem, but until the LFTR thorium reactor is perfected or the fusion technologies of focus fusion or EMC2 polywell fusion is perfected in the next 10~30 years we don't have a solution. I propose that current technologies can be cheap enough and effective at providing the energy required, with one caveat the need to develop and deploy a method to capture solar flux, hydrogen and other gases and store them for use.  If we were to develop and use a bussard ramscoop which I believe is technically possible and feasible we could use inflatable storage spheres to store large quantities of gases expelled from the surface of the sun.  These gases could then be electrostatically separated and stored in their own inflatable storage sphere.  These spheres would be dock-able modules which could be connected in long chains and would carry there own built-in plumbing, electronics, docking, and control mechanisms.   A hydrogen/oxygen/xenon gas acquisition plant could essentially be built either inside the Venus - Earth orbit or the Venus - Mercury orbit to take advantage of the higher solar flux.  Chemical rocket tugs to ferry the resultant gases back into Earth orbit siphoning off some of the stored propellant for its own use, orbiting at L5 or the moon.

That is where the Bloom Box fuel cell comes in, at $700,000 USD it is a steal for the space industry.  At this price point this device can generate the 200kw required by a single vasimr engine, if you have more engines buy more Bloom Boxes.  When mated with the vasimr you would then have an economical and nearly immediately available means of opening up deep space travel today.  The big savings of course the this would obviate the need to launch huge quantities of propellants into space from the earths surface. 

One other thought on the acquisition of Oxygen, many have suggested that we build a space elevator using carbon nanotubes or other superstrong materials.  But, it seems to me that we already have in our possession materials that are strong enough to be lowered and retracted 300 to 400 miles into the upper earth atmosphere to mine gases including hydrogen and oxygen.  This does not get men and equipment into space but it does get critical propellant and oxygen where it is needed.  As a supplemental thought what do you think?

Comments anyone, does anyone share my belief that is a good idea as a solution to providing the power required by the VASIMR?
http://blog.sfgate.com/green/2010/02/24/is-the-bloom-box-the-ipod-of-clean-energy/

ptolemy1977

Offline Jim

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Re: Energy for Space flight.
« Reply #1 on: 04/13/2012 02:02 am »

1. That is where the Bloom Box fuel cell comes in, at $700,000 USD it is a steal for the space industry.  At this price point this device can generate the 200kw required by a single vasimr engine, if you have more engines buy more Bloom Boxes.  When mated with the vasimr you would then have an economical and nearly immediately available means of opening up deep space travel today.  The big savings of course the this would obviate the need to launch huge quantities of propellants into space from the earths surface. 

2.  One other thought on the acquisition of Oxygen, many have suggested that we build a space elevator using carbon nanotubes or other superstrong materials.  But, it seems to me that we already have in our possession materials that are strong enough to be lowered and retracted 300 to 400 miles into the upper earth atmosphere to mine gases including hydrogen and oxygen.  This does not get men and equipment into space but it does get critical propellant and oxygen where it is needed.  As a supplemental thought what do you think?


Sorry, but you need to brush up on your physics and also reread the info in the Bloom Box fuel cell.  The Bloom Box needs air, fuel like natural gas and heat to produce electricity.  And it weighs 17 tons.


The other is that the atmosphere is only about 100 miles thick.  Scooping gases by flying low or using tethers still needs propellant.
« Last Edit: 04/13/2012 02:06 am by Jim »

Offline ptolemy1977

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Re: Energy for Space flight.
« Reply #2 on: 04/13/2012 02:21 am »
Thanks for the comment, but the bloom box requires oxygen like all fuel cells and I am proposing that both hydrogen and oxygen can be harvested from the solar wind.  I am also proposing that potentially it can be harvested by pumping it from the lower atmosphere, which by the way solves the fuel problem you mention since the very act of gathering hydrogen and oxygen from the upper atmosphere would provide any extra fuel that would be required to maintain a low earth orbit, I presume that upon capturing these gases that the siphon and storage tanks would move into a higher more stable orbit, as some satellites do all the time particularly surveillance satellites. 

Offline ptolemy1977

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Re: Energy for Space flight.
« Reply #3 on: 04/13/2012 02:47 am »
Also, I should add that, I do not assume that the bloom box would be used as it is currently designed. But that, it might require further engineering modifications to support modularity and thus make it possible to launch into orbit in stages.  Keep in mind that the point behind the VASIMR is that it is reusable, therefore putting a VASIMR and its power source into orbit is a long term solution for deep space travel they might be used for decades and on many missions this is where the cost savings of this solution come in.  I believe that this proposal addresses the three major components of this design requirement, the rocket engine, its power source, and the fuel for the power source.  That is even if it takes a few launches to get everything into orbit because of the re-usability you get cost savings in spite of that requirement. If this works it is only a question of feasibility and engineering.

Offline Jim

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Re: Energy for Space flight.
« Reply #4 on: 04/13/2012 03:22 am »
Thanks for the comment, but the bloom box requires oxygen like all fuel cells and I am proposing that both hydrogen and oxygen can be harvested from the solar wind.

not feasible
Solar wind is just charge particles, mostly electrons and protons.  No oxygen and its density is 3-6 atoms per cubic centimeter.  That is too low of density to collect.

  That is why every depot scheme use hydrogen and/or water brought up from earth or the moon.
« Last Edit: 04/13/2012 03:35 am by Jim »

Offline Jim

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Re: Energy for Space flight.
« Reply #5 on: 04/13/2012 03:25 am »
I am also proposing that potentially it can be harvested by pumping it from the lower atmosphere, which by the way solves the fuel problem you mention since the very act of gathering hydrogen and oxygen from the upper atmosphere would provide any extra fuel that would be required to maintain a low earth orbit, I presume that upon capturing these gases that the siphon and storage tanks would move into a higher more stable orbit, as some satellites do all the time particularly surveillance satellites. 

Not feasible.
there isn't enough hydrogen to be captured to make it worth while.  All the skimming proposals are for oxygen or nitrogen.

Offline Jim

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Re: Energy for Space flight.
« Reply #6 on: 04/13/2012 03:29 am »
Also, I should add that, I do not assume that the bloom box  long term solution for deep space travel they might be used for decades and on many missions this is where the cost savings of this solution come in.  I believe that this proposal addresses the three major components of this design requirement, the rocket engine, its power source, and the fuel for the power source. 

There is no fuel for deep space, in space to be harvested.

PS.  A bloom box is for hydrocarbon fuel.  if you are planning on hydrogen, then existing fuel cells are useable.  But as stated there is no free hydrogen available.

Offline ptolemy1977

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Re: Energy for Space flight.
« Reply #7 on: 04/13/2012 04:28 am »
Jim thanks again for your insight.  I agree that as you've pointed out that the particle density of the solar wind even close to the sun is too low to be effectively captured as a fuel source.  Furthermore, I am not necessarily tied to the commercial product the bloom box but rather the idea of using a fuel cell, the bloom box is just a popular product that many people and corporations are thinking about to produce fuel for them.  To simplify, the point is to use hydrogen and oxygen gathered from either of these two sources, whereas I agree that the solar wind may not be a viable source no matter where a collector is placed in the solar system I am not convinced that capturing gases from the atmosphere is impractical.  I also do not agree that no elemental hydrogen can be found in the upper atmosphere, wiki exosphere the article there points out that in the exosphere hydrogen is the major component.  That said I am not looking for hydrogen in the exosphere nor the thermosphere, but rather from the mesosphere 50 miles above the earths surface where the particle density is still rather high, see the following chart http://en.wikipedia.org/wiki/File:Atmosphere_model.png.  I am suggesting that in spite of previous views of the topic of mining gases from the upper atmosphere that we might re-investigate the feasibility in the light of new materials, and that hydrogen and oxygen could potentially be mined from the mesosphere from a very low earth orbiting satellite, one that might even dip into the exosphere or even the thermosphere to facilitate gathering the gases.

Offline Jim

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Re: Energy for Space flight.
« Reply #8 on: 04/13/2012 04:36 am »
  I am suggesting that in spite of previous views of the topic of mining gases from the upper atmosphere that we might re-investigate the feasibility in the light of new materials, and that hydrogen and oxygen could potentially be mined from the mesosphere from a very low earth orbiting satellite, one that might even dip into the exosphere or even the thermosphere to facilitate gathering the gases.

Not feasible, too much drag and too much heat.  It would not be orbiting but reentering.  The drag would more than the energy collected.
For the shuttle, entry started at 400,000ft.

There are no "new" materials that make the idea more viable now than 10 or 20 years ago.

Again, the point was oxygen or nitrogen and not  Hydrogen.  It is too rare, and takes too much energy to compress and liquify.

And at any rate, the idea is to generate more energy than what is used.  Atmosphere skimming requires outside energy such as solar power.

And two more points.
A.  Skimming does not get you energy for deep space. 
b.  Converting chemicals into electricity for VASMIR is bad idea.  There are too many losses.  Just burn the propellants in a normal rocket
« Last Edit: 04/13/2012 04:41 am by Jim »

Offline DarkenedOne

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Re: Energy for Space flight.
« Reply #9 on: 04/13/2012 04:36 am »
I am new to this forum, I had an idea that I would like to share regarding the use of the vasimr in deep space exploration.  It is clear that the hold up in its use will be providing a sufficiently large power source for this device.  I was thinking about the convergence of several technologies which might address the problem.  1) the bloom box, or fuel cell. 2) bussard ramscoop 3) inflatable storage mediums 4) chemistry.

The problem with deep space travel is the need to go fast and far this requires a lot of fuel or a high density energy source.  Nuclear has often been kicked around as the possible solution to energy density problem, but until the LFTR thorium reactor is perfected or the fusion technologies of focus fusion or EMC2 polywell fusion is perfected in the next 10~30 years we don't have a solution. I propose that current technologies can be cheap enough and effective at providing the energy required, with one caveat the need to develop and deploy a method to capture solar flux, hydrogen and other gases and store them for use.  If we were to develop and use a bussard ramscoop which I believe is technically possible and feasible we could use inflatable storage spheres to store large quantities of gases expelled from the surface of the sun.  These gases could then be electrostatically separated and stored in their own inflatable storage sphere.  These spheres would be dock-able modules which could be connected in long chains and would carry there own built-in plumbing, electronics, docking, and control mechanisms.   A hydrogen/oxygen/xenon gas acquisition plant could essentially be built either inside the Venus - Earth orbit or the Venus - Mercury orbit to take advantage of the higher solar flux.  Chemical rocket tugs to ferry the resultant gases back into Earth orbit siphoning off some of the stored propellant for its own use, orbiting at L5 or the moon.

That is where the Bloom Box fuel cell comes in, at $700,000 USD it is a steal for the space industry.  At this price point this device can generate the 200kw required by a single vasimr engine, if you have more engines buy more Bloom Boxes.  When mated with the vasimr you would then have an economical and nearly immediately available means of opening up deep space travel today.  The big savings of course the this would obviate the need to launch huge quantities of propellants into space from the earths surface. 

One other thought on the acquisition of Oxygen, many have suggested that we build a space elevator using carbon nanotubes or other superstrong materials.  But, it seems to me that we already have in our possession materials that are strong enough to be lowered and retracted 300 to 400 miles into the upper earth atmosphere to mine gases including hydrogen and oxygen.  This does not get men and equipment into space but it does get critical propellant and oxygen where it is needed.  As a supplemental thought what do you think?

Comments anyone, does anyone share my belief that is a good idea as a solution to providing the power required by the VASIMR?
http://blog.sfgate.com/green/2010/02/24/is-the-bloom-box-the-ipod-of-clean-energy/

ptolemy1977

High grade U-235 is the simple answer.  The reactors on nuclear subs are about the size of a trash can and generate 33 MW. 

Of course generating this power from heat in space is difficult.
« Last Edit: 04/13/2012 04:39 am by DarkenedOne »

Offline ptolemy1977

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Re: Energy for Space flight.
« Reply #10 on: 04/13/2012 04:57 am »
Jim, I am starting to believe that you don't like my idea.  Huge loses would be a bad thing if chemical generation of electricity cannot provide the electricity required to power the VASIMR over time then it is in fact not feasible.  I guess my issue was that if we had a readily available source of chemical fuel would it be practical to use a fuel cell to generate enough electricity to power the VASIMR for the 1~2 months required for a round trip to Mars or for some other deep space scenario?  your answer appears to be no that the fuel cell would be too inefficient thus requiring too much hydrogen to be feasibly stored and transported.  If all of these ideas hold true then I am forced to agree that this idea would not work.  Its been fun!

Darkendone,  I agree that the most feasible answer is some type of nuclear.  But, I did not know that the government would allow the use of a submarine nuclear generator for space flight purposes?  I have seen on many boards that there isn't a nuclear reactor available to NASA which is large enough to power the VASIMR.  Night folks, maybe I'll post again someday.

Offline alexterrell

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Re: Energy for Space flight.
« Reply #11 on: 04/13/2012 07:44 am »
Thanks for the comment, but the bloom box requires oxygen like all fuel cells and I am proposing that both hydrogen and oxygen can be harvested from the solar wind.

not feasible
Solar wind is just charge particles, mostly electrons and protons.  No oxygen and its density is 3-6 atoms per cubic centimeter.  That is too low of density to collect.

  That is why every depot scheme use hydrogen and/or water brought up from earth or the moon.
or Phobos / Diemos.

One other exception was the Bussard Ramjet, which scooped up interstellar hydrogen to use in a fusion reactor. This was great for science fiction (esp Larry Niven) but:

1. according to Zubrin would generate more drag than thrust
2. Relies on 4H -> 1He fusion reaction, which we can't get close to

Offline gbaikie

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Re: Energy for Space flight.
« Reply #12 on: 04/13/2012 07:47 am »
Jim, I am starting to believe that you don't like my idea.  Huge loses would be a bad thing if chemical generation of electricity cannot provide the electricity required to power the VASIMR over time then it is in fact not feasible.  I guess my issue was that if we had a readily available source of chemical fuel would it be practical to use a fuel cell to generate enough electricity to power the VASIMR for the 1~2 months required for a round trip to Mars or for some other deep space scenario?  your answer appears to be no that the fuel cell would be too inefficient thus requiring too much hydrogen to be feasibly stored and transported.  If all of these ideas hold true then I am forced to agree that this idea would not work.  Its been fun!

Darkendone,  I agree that the most feasible answer is some type of nuclear.  But, I did not know that the government would allow the use of a submarine nuclear generator for space flight purposes?  I have seen on many boards that there isn't a nuclear reactor available to NASA which is large enough to power the VASIMR.  Night folks, maybe I'll post again someday.

A kg of Hydrogen is about 40 kw hours of energy [plus the oxygen. With rocket fuel one uses 6 kg of oxygen per 1 kg of Hydrogen. I suppose fuel cell is 8 kg to 1 kg of hydrogen, so 9 kg per 40 kW hours*].
At earth distance one gets 1360 watts per square meter. Suppose solar panels have 25% efficiency. So square meter of solar panel gives: .34 kW. Or 8.16 kW hours per day. And 57.12 kW hours in a week. 

A VASIMR stands for "Variable Specific Impulse Magnetoplasma Rocket"
And "VASIMR is intended to bridge the gap between high-thrust, low-specific impulse propulsion systems and low-thrust, high-specific impulse systems. VASIMR is capable of functioning in either mode"
http://en.wikipedia.org/wiki/Variable_specific_impulse_magnetoplasma_rocket

Generally if you have long burn times of days to weeks, one would get more energy per weight with solar panel.
If VASIMIR were designed for high thrust- burn time of minutes to an hour or so, then perhaps one could use chemical energy.

*this does not include inefficiency of converting this chemical energy into electrical energy- which I believe is somewhere around 50%.
« Last Edit: 04/13/2012 07:55 am by gbaikie »

Online 93143

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Re: Energy for Space flight.
« Reply #13 on: 04/13/2012 08:10 am »
Higher specific impulse (lower mass flow rate for a given thrust) means higher exhaust velocity, and since energy is proportional to the square of velocity, this means higher power requirements for the same thrust; that is, higher energy requirements for the same impulse.

The upshot of this is that for any energy-containing substance, the largest delta-V is obtained by firing it out the back of your spaceship with as much as possible of its potential energy converted to directed kinetic energy.  Chemical rockets do this reasonably well.  Fission fragment rockets (or directed fusion product rockets) are the nuclear equivalent.  A nuclear-powered VASIMR is far less efficient than a fission fragment rocket, but it's way easier to do and probably capable of higher thrust.

In the case of a chemical fuel cell powering a VASIMR, the chemicals have to be either kept on board or dumped at low energy, neither of which provides a whole lot of delta-V.  And VASIMR can't generate anywhere near the thrust of a chemical rocket given the same energy flow rate.  Not to mention that this scheme would be far more massive than a chemical rocket system, which is very bad for performance even if all else is equal, which it isn't.  I'm afraid it fails horribly on all counts.

Just for some perspective:  the RL-10B-2 is a small hydrogen/oxygen engine for in-space use that produces 24,750 lbs of thrust.  It weighs only 277 kg, and produces 250 MW (yes, megawatts) of jet power (the directed kinetic energy per second in the exhaust) at about 80% efficiency.  Each kilogram of stored chemicals provides 4550 N·s of impulse.  The OP's scheme falls very, very short of every single one of these metrics.

As for powering a VASIMR with a nuclear reactor, there are some ideas.  Here's one:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110009914_2011009270.pdf

Offline Nomadd

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Re: Energy for Space flight.
« Reply #14 on: 04/13/2012 11:22 am »
 Harvesting gasses from the atmosphere is nonsense. You still have to accelerate that material to orbital velocity, same as if you launched it with a rocket. There's no way that system will ever be as cheap as just launching tanks of fuel. When 90% reliability for your low value cargo launchers is acceptable, they'd get a whole lot cheaper.

 Reactors in subs have the ocean for a heat sink. There's a lot more to making electricity than just generating heat.
 
 As far as using fuel cells to buffer solar for high thrust periods, the latest battery technology stores about 8 times as much power per kg as the nickel/hydrogen batteries on the ISS and is a helluva a lot more efficient than any two way chemical/power conversion will ever be. If VASIMR ever made it to the ISS for testing, that's probably how they'd have to do it, since there's very little chance they're going to get 200kw delivered to them.
« Last Edit: 04/13/2012 11:26 am by Nomadd »
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Offline DarkenedOne

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Re: Energy for Space flight.
« Reply #15 on: 04/13/2012 02:41 pm »
Jim, I am starting to believe that you don't like my idea.  Huge loses would be a bad thing if chemical generation of electricity cannot provide the electricity required to power the VASIMR over time then it is in fact not feasible.  I guess my issue was that if we had a readily available source of chemical fuel would it be practical to use a fuel cell to generate enough electricity to power the VASIMR for the 1~2 months required for a round trip to Mars or for some other deep space scenario?  your answer appears to be no that the fuel cell would be too inefficient thus requiring too much hydrogen to be feasibly stored and transported.  If all of these ideas hold true then I am forced to agree that this idea would not work.  Its been fun!

Darkendone,  I agree that the most feasible answer is some type of nuclear.  But, I did not know that the government would allow the use of a submarine nuclear generator for space flight purposes?  I have seen on many boards that there isn't a nuclear reactor available to NASA which is large enough to power the VASIMR.  Night folks, maybe I'll post again someday.

Even time NASA gets remotely serious about going into deep space and establishing a presence on places like the moon and mars nuclear power comes up as being one of if not the best method of producing the significant power requirements.  However ever time the program gets cancelled well before anything is fully developed.

When the US government gets serious about space exploration we will get serious about space nuclear power and VASIMR. 

 

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