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Hello and greetings. Yeah, I know, another newbie. Gotta start somewhere.
I have spent the last several hours reading the posts here, and I do have a few questions.
Some of you have posted information of NSWRs, NTRs and GCNTRs.
I realize that NERVA did a bit of research on much of these, but where are we now? Please corect me if I have any errors in my understandings:
NTR: basically a Uranium core that heats H2 with Impuse of 900-1000. Later NERVA experiments resulted in NTRs with around 10 hours of operation that had, for the most part, elminated the cracking of the fuel rods
GCNTR: NTR with a gas core, never actually built, but looks great on paper (?), Impulse of around 2,000-4,500? Uranium suspended in a magnetically confined reaction chamber-gas used is again H2
NSWR: Nuclear salt-water rocket? It sounds similar to a GCNTR, but uses saltwater as propellant? Theoretical Impulse=?, Operational hours=?, Does it require weapons-grade material or less (hopefully less)
I suppose what I'm really asking here is where does technology stand on a NSWR, and which would be a more practical powerplant for interplanetary flight: GCNTR or NSWR?
I'd like to have a better understanding of all this.
Apologies for the intrusion, and thanks for replying.
Sure people dream about space travel. There's nothing wrong with that. Everything humankind has made, was once but a dream.
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NSWR. Heat is the only real problem with that system--fuel injection tech is about all that is needed. NTRs will probably come first, since we know more about that than any other system. NSWRs may come next--with other more advanced systems coming later, perhaps.
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Welcome to New Mars...
The problem with all nuclear fueled options is that they do tend to attract a lot of opisition. But with the world changing there is a growing public awareness that Nuclear is the only way to ensure a lot of countries get to keep there lights on and this will flow towards Nuclear options in space and into more public acceptance for that option.
Chan eil mi aig a bheil ùidh ann an gleidheadh an status quo; Tha mi airson cur às e.
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I think NSWR might be alot closer than you might think. Belive it or not, the basic concept is sound enough. Nuclear chain reactions can occured in water, and this has unfortunatly been demonstrated a great many times in various criticality accidents, some of which have been fairly violent. Extending this principle to a full-blown explosion might then be possible.
But of course there are still issues. Like keeping the solution from going critical BEFORE you want it to (like in one of those criticality accidents I mentioned above), this is generaly much more difficult to achive in a liquid solution then a solid one, as the velocity of the liquid can effect the neutron flux. Zubrin planned to counter this by placing the fuel in large, fairly thin tubes made from a neutron absourber. But in the complex plumming of such a system and with the added influence of the rockets acceleration, this might not be enough. If a criticality accident DID occur and one of the tubes was breached, it could be a fatal disaster for the rocket as one breach could lead to others, and a larger volume of the fuel going critical. Repair in the face of all that radiation would be difficult to impossible.
The liquid fuel for the rocket is just generaly nasty stuff. 30% Enriched Uranium disolved in a barium salt. Radioactive, poisonous, and threatens to go critical if present unmoderated in to large quantities. Manufacturing and transporting it to orbit could be serious issues. Since it obviously has the potential to produce a nuclear explosion, (or be used in a weapon, 30% enriched fuel is good enough) security is also important.
He who refuses to do arithmetic is doomed to talk nonsense.
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Agreed
Its probably the easiest of any of the "super engine" concepts engineering wise, but the devil is in the details, and the stuff is dangerous to handle. I don't even want to think about a launch failure with a tank of this stuff, even me the quintisential nuclear fan boy cringes at that.
Bringing up the salt and water separatly is the best way, but handling water in the freezing cold/burning heat/vacuum of space could prove to be tricky. If you lose some of the water, the concentration of the Uranium increases, and will go critical neutron absorber or no.
In fact, if the stuff does anything besides exactly what its supposed to do, it will go critical inside someplace you don't want it to.
Long-term, thinking about colonizing Mars or mining asteroids or whatnot, the amount of Uranium needed starts to add up. Better to go with GCNR or VASIMR when all you need it Hydrogen and the occasional small amount of Uranium.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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In other words, it is a high-risk (high "Oops" factor, high "kaboom" factor), high-reward rocket (high thrust, high Impulse) whose use is possibly fine, provided you're not the person riding it, or are anywhere near it.
Thank you for the warm welcome and the great access to information. I look forward to conversing with you all in the threads to come. 8)
Sure people dream about space travel. There's nothing wrong with that. Everything humankind has made, was once but a dream.
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This is one of the reasons why I think the Sea Dragon concept would fit well with NSWRs. Both the NSWR payload and the Sea Dragon booster need large amounts of water. We are already seeing "Spars" like the Neptune being up-ended in ocean that are as large or larger than Sea Dragon.
So, Sea Dragon--in a fashion--is already being built--as the Neptune Spar.
Space-elevators may use this tech as well
http://www.kerr-mcgee.com/operations/in … /index.htm
http://www.jraymcdermott.com/spartec/sp … istory.htm
http://www.rigzone.com/data/projects/pr … ject_id=32
http://www.corrpro.com/solutions16.htm
http://www.offshore-technology.com/projects/neptune/
http://www.tamu.edu/univrel/aggiedaily/ … 896-2.html
http://www.jraymcdermott.com/projects/Neptune__27.asp
http://uplink.space.com/showflat.php?
http://channel.nationalgeographic.com/c … sodes.html
http://www.anvilpub.com/epn_december.htm
Flexscraper for Space elevator guide channel?
http://www.livescience.com/technology/0 … raper.html
Very large nautical structures would allow very strong hulls that NSWR will doubtless need, plus the payload is only water.
A seperate launch of the actual nuclear material would be done out of baikonur.
Hujsak wrote a book calling for the large spherical tanks (that will be in production shortly for new LNG terminals) to be used for large, Phil Bono type craft. He called this craft a ULLV.
I think nautical firms may be the answer for very large spacelift.
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You can't use a plain old water tank for an NSWR though, if you did that it would blow up and vaporize the ship and the fuel station. An NSWR fuel tank is comprised of long narrow tubes of a neutron absorbant material stacked side-by-side. If not, the Uranium would go critical, and kaboom.
SeaDragon doesn't need large amounts of water, it needs large amounts of Hydrogen and Oxygen. SeaDragon's upper stage engine would also be far too powerful to fire in space.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Hi GCN: Why is there an upper limit on the power in space? If the thrust is 2 million pounds, that accellerates a million pound spacecraft at 2g = 64 feet per sec per sec = 19 meters per second per second? Neil
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I don't really follow your question, Neil
Probably the central truth and the central problem of all spaceflight is summed up neatly in Tiokovski's famous "rocket equation" which can be found at various websites, anyway: in order to accelerate you have to push (usually burn) fuel to speed up, and the faster you want to go the more fuel you need, but amount of fuel needed increases exponentially with speed.
In theory it doesn't really matter how quickly you burn the fuel, you still need the same amount to reach the same speed reguardless how much thrust you have, and this holds true within ~10% most of the time. The question mark is how quickly you want to accelerate, like a whimpy ion engine with a few pounds of thrust would take years to reach Mars while a rocket would take months.
You could pack very many/very big engines on the back of a rocket to achieve very high thrust and very short acceleration times, but you get rapidly diminishing returns when you are talking thousands of pounds of thrust, the total trip time difference between accelerating in ten minutes instead of ten hours is not large. Each/bigger engine adds mass, which subtracts from payload too.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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You can't use a plain old water tank for an NSWR though, if you did that it would blow up and vaporize the ship and the fuel station. An NSWR fuel tank is comprised of long narrow tubes of a neutron absorbant material stacked side-by-side. If not, the Uranium would go critical, and kaboom.
SeaDragon doesn't need large amounts of water, it needs large amounts of Hydrogen and Oxygen. SeaDragon's upper stage engine would also be far too powerful to fire in space.
I don't know that it would be too powerful. The NSWR payload itself will be in the form of tubes as you say--and will thus be a substantial payload--and this is perfect for Sea Dragon. An NSWR needs to be overbuilt to handle the heat as a heat sink, for shielding, etc. Therefore the rugged construction methods for the conventional Sea Dragon will also serve for the dedicated NSWR 1st and second stages. NSWR itself will fire in orbit.
Nice links:
http://en.wikipedia.org/wiki/Sea_Dragon_%28Rocket%29
An NSWR fueling station station needs to be kept in a higher orbit to be safe--warranting larger LVs.
Almost over:
http://www.aero.org/conferences/sclv/
Misc:
http://www.efluids.com/efluids/pages/j_ … d_rock.htm
http://www.lpi.usra.edu/CASS_home.html
OT
R.E. Gold, 'SHIELD: a comprehensive earth protection architecture', Advanced Space Research, vol 28, 2001, pp1149-158
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Such a massive engine (~6.4 million kilograms of thrust!) is extremely overkill for any concieveable orbital transit short of a city-sized rocket. Building it such that it would be reliably restarted, particularly after extended orbital storage, would be incredibly difficult especially since it is both pressure fed and cryogenic.
Why would you need to put an NSWR fueling station into high orbit? The fuel is just Uranium-235, which is not particularly dangerous in the superlow concentrations that people on the ground would be exposed to. The only real threat is a criticality event, which shouldn't be a big hazard if the Uranium salt is mixed with the water propellant only during loading of the NSWR tanks with neutron absorbant plumbing.
NSWR probably won't have dedicated stages persay, although disguarding empty fuel tube bundles after firings would improve payload/trip time a bit. The engine/heat shield will be heavy enough that you would only want to carry one of them. The shield itself should not be too outrageous and could be lifted on lighter rockets than SeaDragon.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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If that is true we might get it on a CaLV. Maybe so, maybe not.
Sea Dragon may not be over kill in that folks would want NSWR ignition as far away as possible. Sea Dragon really isn't that big compared to Spars, Troll, etc.
It is probably the biggest rocket we could use--and would not need a pad.
The reason I have an interest is that the same building process would get support columns mass produced for a future Bering Strait Bridge, and large metal tubes would find use perhaps as alternative energy (wave action) booms. I'm pro-nuclear myself--but if we can siphon money from future alt. energy schemes--why not get 90% of a big rocket production line out of it at the same time.
I simply want to see the size of LVs increase--while keeping them simple.
Sprague's Arcturus concept would still be pressure-fed--but have some turbopumps for other purposes--and use all hydrogen.
My scheme is that a very heavy NSWR would be made using shipyard construction. It would be placed atop Sea Dragon. That LV fires normally, and the NSWR ignites.
Later Sea Dragons launch pure water to orbit--with the empty tanks used at station modules. The nuclear salts themselves would then be launched atop CaLV, or perhaps even UR-500 Proton--well away from anti-nukes.
Heavy duty replacement nozzles would be cones launched atop Sea Dragon--as that LV's noscecone.
Remember--NSWR is a constant fission reaction--a steady nuclear explosion if you will. You had better have a rugged nozzle for that.
Sea Dragon isn't really that big compared to the Neptune Spar.
Drawing:
http://en.wikipedia.org/wiki/Sea_Dragon_%28Rocket%29
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You keep trying to make SeaDragon sound like a "modest" sized rocket by comparing it to other things, SeaDragon is not modest it is the very height of extreme engineering.
There are diminishing returns when dealing with ultra-heavy rockets like this, that timely launch would be hard, the granularity of the payload is very poor, and I am wary of launching an entire ship or other expensive payload... as they say about eggs in baskets.
One issue with SeaDragon is what you do with the payload when its on orbit, the thing is so big and heavy that maneuvering it to dock or aim a rocket engine would be problematic.
There is a such thing as too big... if you need marginally lower launch costs, like you would get with SeaDragon, a spaceplane would be better.
[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]
[i]The glass is at 50% of capacity[/i]
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Setting the Sea Dragon issue (which I'm not a big fan of) there are a couple other issues with your last post.
- First, the fueling station in orbit. I think this is a difficult to impossible concept. In theory it is good, transport up the water (no problem) and Uranium Salts up in seperate bundles. However, transporting this realitivly highly enriched uranium salt up to orbit is no picknick. Undiluted in water the salt will go critical in even smaller concentrations than the diluted mixture would. In the right conditions it is even possible for it to go super-critical (ie. nuclear bomb). This means the salt must also be diluted in some way (mix graphite in with or something) or moderated in a similar method that the liquid fuel is.
Obviously the container for the Salt has to be very rugged, as not only is the stuff radioactive and probably toxic, it is also in more danger of going supercritical if the rocket should explode. If the containment system failed and the salt was compressed by an explosion (or by strong aerodynamic forces) a nuclear explosion in not impossible. This is a problem for the liquid form as well, but since the mixture is diluted it is less likely (though a major criticality accident is a real possibility).
After you get the stuff to orbit, mixing it together is by no means a simple and easy process, even less so in 0g. Rember, the neutron flux of this mixture changes as it's velocity changes, so their are some real hazards involved during the mixture process. A criticality incident could very well destroy your fuel depot and will definetly cause serious damage to it. I won't go so far as to say it's impossible, but it's far from easy, it's probably not an easy mixture to make here on Earth, with gravity to help simplify things, and much better safety percautions.
Considering these two factors, it seems to me that transporting the fuel up already-mixed is a much better solution then a fuel depot.
- Next, there is no reason the engine has to fire continusly. It has the potential to certianly, but in many ways using a pulsed system would be simpler. Obviously pulsing the detonations would give the engine nozzle time to cool of, and so it could be lighter. Additionaly an engine cone might be done away with altogether. This would reduce it's efficency, but could save a great deal of mass. It might be simpler for the pumping system to fire in spurts (maybe with a piston pushed design).
Pulsed firing is slightly less efficent than continuous firing, but not signifigantly so. A NSWR has absurd levels of thrust anyways, so extending the burn time to twice as long or more most likely will not signifigantly effect efficency. Even if the burn time was MUCH longer (days as opposed to hours) the diffrence in the oribtal path the rocket would have to take would not be that signifigant in terms of delta-V. It would be a slightly less efficent use of the nuclear fuel (the leading and trailing stream bits will have the lowest efficency), but again the NSWR ISP is so huge that this may be a saccrifice worth making, and this loss of effiency is probably not that great anyways (depends upon the length of the pulse of coures though).
- If the NSWR proves to heavy for ground lift (a possibility) then it might prove practical to launch the fuel and engine segments seperatly, or just the engine and crew portions seperatly. I don't know if we have addressed this, but the crew will need to be seperated and/or shielded from the engines not-insignifigant radiation as well.
He who refuses to do arithmetic is doomed to talk nonsense.
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I'm not a big fan of spaceplanes and assembly myself. We produce a lot of spars and jack-up rigs. People just have this mental block when it comes to going the next step in LVs. Orion was too big. Sea Dragon isn't.
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I spent a little time looking into the Nuclear Salt Water Rocket proposed by Robert Zubrin. I believe that the concept (as it stands) is unlikely to be workable.
The reason is that neutron reproduction factor and reactivity in a moderated mixture tends to decline with increasing temperature. Take a look at the graphs for neutron reproduction factor.
http://dspace.mit.edu/bitstream/handle/ … ture06.pdf
The mixture would be injected cold (when reactivity is greatest and average neutron energy is 0.025eV) and as it heats up (and average neutron energy increases), the reaction would tend to dampen as reproduction factor declines.
Notice however that in the fast neutron region (>1KeV), the reproduction factor increases with increasing neutron energy (i.e. temperature). This suggests that Zubrin's rocket would work well for all fissile fuels at high neutron energies. This suggests that the rocket would work best if the fuel was injected as pure molten uranium or plutonium chloride, with no water present. Any hydrogen injected with a temperature lower than 10million K (1KeV) will tend to dampen the reaction.
Last edited by Antius (2017-07-06 05:36:31)
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