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NASA Looking At Nuclear Thermal Rockets To Explore the Solar System
MarkWhittington writes: Officially, NASA has been charged with sending astronauts to Mars sometime in the 2030s. Toward that end, according to a story in Universe Today, space agency engineers at the Marshall Space Flight Center are looking at an old concept for interplanetary travel, nuclear thermal engines. "...according to the report (cached), an NTP rocket could generate 200 kWt of power using a single kilogram of uranium for a period of 13 years – which works out of to a fuel efficiency rating of about 45 grams per 1000 MW-hr. In addition, a nuclear-powered engine could also provide superior thrust relative to the amount of propellant used." However, some doubts have been expressed whether NASA will be granted the budget to develop such engines.
I have been stumping for this since they decided to retire the shuttle. Stop building big rockets to toss things away from Earth. Get it in orbit and use prestationed nuclear rockets to move it to and from higher orbits. Would just need to refuel them occasionally.
OMG nu-cle-er radiashun in space! Think of the environmental damage!
*thank* you yeah. No more imperial shit.
> which works out of to a fuel efficiency rating of about 45 grams per 1000 MW-hr.
And we all know just how incredible that is! Right?!? Everybody?
I just love it when one obscure number is 'explained' by yet another obscure number. Was it beneath the submitter to compare it to gasoline, or rocket fuel, or something the general audience here already has some kind of context for?
What an emotionally charged word :"explore". The Solar System's mostly empty. Big deal. What's to explore?
there's NASA's killer app: a Hybrid Rocket. distracts the anti-nuke/global warming crowd.
Elon Musk is going to be responsible for exploring the galaxy as a ruling immortal being. There is no doubt he will become ruler of the cosmos. You can either support him now or be left behind on Earth as a mortal. The choice is yours.
ok.../. cut off the "ket"....but roc is cool, too.
An Ion thruster (of any variety) is not *remotely* a replacement for a nuclear thermal engine. The ISP is great but the thrust levels are (and always will be, at rational sizes) feeble. And it's very likely that massively clustering them to get the thrust up will required a nuclear reactor to power them. 6/10ths of an *ounce* of thrust for 4 kW power input.
Ion thrusters have their uses, like in gently nudging things over long periods. They are not going to replace chemical rocket or NTP engines for any sort of high-thrust application.
I wish! This kind of technology was lost in the 60's and 70's, financially speaking. This is just like the nuclear car, never actually gonna happen. Sad.
discover the secrets of the universe, advance our technology, and enhance our national prestige. Now, the hard part is that we want you to do that with a budget of $10 Canadian, and a used shoestring we got from a hobo. Now get to it team.
"However, some doubts have been expressed whether NASA will be granted the budget to develop such engines."
not if repubs are concerned, unless they build them in like alabama or something.
At the Europa day on the Hill last summer, I ran into a 90 yr old Harry Finger (the former head of NERVA) who remains absolutely convinced that this technology (which was ready for flight tests back in the Apollo period) is essential for human travel to the planets, and needs to be revived.
Looking at the delta-V requirements for a human Mars mission, I can't say I disagree with him.
You mean Jimmy Carter?
we can start by exploring ur anus.
I am pretty sure they did that in the '60s during that period's Jesus-gap scare. They got to the moon, but didn't find Jesus, so it was ultimately a failure. However, to try to save face they moved the goalpost and just settled with landing someone there and planting a flag and saying it was a success over and over again until it became truthy enough to be the only thing in the history books.
He'd need to consult Amih on any nuceur policy.
NASA had the NERVA project from 1952-72. They actually made a working test article, too! The project got axed because of "give a mouse a cookie" syndrome -- Congress figured that, if they let NASA make a nuclear rocket suitable for a Mars mission, people would want to make it happen, and they didn't want to spend money on sending humans to Mars when that money was better spent on...whatever else was going on in '72 (Watergate? Vietnam?).
A gasoline-powered rocket was probably a bad idea during the 1970's oil crisis. Salvage 1 would have worked better back then.
Cars do not have gasoline? Trains and ships do not have diesel? Airplanes do not have kerosine?
The only vehicles that do not carry it's own reaction mass are gliders.
"Miserable failed end"? NERVA worked! NASA had an engine that could run for hours on end by the end of the program. The project was axed by Congress because they didn't want NASA to make a rocket that could go to Mars because if they did, people would want NASA to go to Mars (and thus want money spent accordingly).
Fancy lithium battery powered nut drivers work, but Crescent wrenches do just fine without anything but your hand.
Use what works.
No other mode of transportation has to carry its own reaction mass and throw it away. Not bicycles, cars, trains, ships, submarines, or airplanes.
Quite right. Because no other form of transportation takes place in a vacuum. Unless you know of some radical new physics, standard reaction-mass engines will be necessary for spaceflight for... well, forever, so, I'm not sure exactly what your point is. And yes, they've worked on the idea before with NERVA. We have, believe it or not, made a few technological and engineering breakthroughs since then (mind you: NERVA worked. It worked very well. It was canceled for political reasons, not practical ones).
"None can love freedom heartily, but good men; the rest love not freedom, but license." --John Milton
A rifle doesn't need enough propellant to shoot itself, only a bullet. If you stop adding thrust after and initial kick in the ass you can use an asteroid, moon, or planet for your reaction-mass.
and reality, hope wins the money run every time
There will never be a nuclear thermal engine with an exhaust velocity higher than the melting point of the nozzle materials used (circa 3800 F) and thus, not one single iota of longer range flight for a given rocket size.
What's available for non-electrical accelerators is thermal velocity exhaust which most of us know means a maximum final Delta V from source of circa 58,000 ft/sec and that won't even get us to Jupiter in a lifetime (baring gravitational slingshots, an entirely different issue)
And electrical conversion of thermal energies are losers, with a minimum of 50% of the energy lost as radiant heat (Thanks Carnow).
So, nothing good here. Unless you can fission and confine the daughter products without mechanical contact (think gas fission at plasma temperatures) you will not go any faster than a chemical rocket would move you over a trans-martian orbit.
You mean Jimmy Carter?
Jimmy Carter is an engineer with credentials which give him
ability to make intelligent and informed comments on nuclear
technology.
You, on the other hand, are just some smart-mouthed prick
who will never accomplish anything worthwhile in your miserable
piece of shit existence.
.
Leaving aside how ridiculous your argument is, I'll poke some holes in your math instead. To paraphrase XKCD, space is not high, space is fast. LEO is 7.8 km/s. Accelerating 118 tonnes to 7.8 km/s takes 3590 GJ, significantly more than the 232 GJ you mention.
There was, and probably still is, far more nuclear material airborne 24/7 in standby aircraft. That's in actual bombs, too, with all the many other components assembled to cause it to explode, whereas the thruster would be contained to provide protection as used in currently launched devices.
ancient discredited NERVA/ROVER program which began in 1956 and dragged on to a miserable failed end in 1973
You mean the discredited program that produced working engines and test-fired them on vacuum stands, proving they are practical and work? You might also note another program that was terminated in 1972: Apollo. Oh my, what an abominable failure that one was...
the fact that any rocket has to carry and throw away a vast load of reaction mass
And how else would you propose to move in space? Mr Newton might have something to say here.
But the actual raw energy needed to lift 118 tonnes to 200 km is...
If you think the difficulty in achieving orbit is just lifting something sufficiently high up, you're more dense than I thought... Here's an idea, first learn about something, then start lecturing about it.
No other mode of transportation has to carry its own reaction mass and throw it away. Not bicycles, cars, trains, ships, submarines, or airplanes.
Please note that all of the above modes of transportation have one thing in common: they only work on the Earth. Or when was the last time you last saw a car drive through outer space?
That big rocket is mostly just to put the payload into orbit. Once in a low earth orbit, it doesn't take that much more to take it from there to a different orbit.
This xkcd is probably the best way to grasp the difficulties of 'getting into space".
https://what-if.xkcd.com/58/
Prediction for end of Universe #42: Fencepost error in Quantum_bogosort.cpp
The reaction mass is not the fuel. Fuel is fuel and provides the energy for accelerating forward. But in order to accelerate forward you must push against something. That something is the reaction mass.
Cars, trains push against the earth. Boats push against the water. Airplanes push against the air. The earth, water and air are all more massive than the things pushing against them, so the less massive thing accelerates forward. That's easy to visualize.
Rockets however push against the mass of the fuel they carry. So the fuel has to be heavier in order
No, I said Ted Cruz and I meant it.
http://www.slate.com/blogs/bad...
We are stupid and will die on this rock before we figure out how to get off it.
What if it were China doing this?
Or Russia.
Or, god forbid, North Korea.
And remember cockups are not the sole preserve of foreigners.
You mean Jimmy Carter?
Jimmy Carter is an engineer with credentials which give him
ability to make intelligent and informed comments on nuclear
technology.
You, on the other hand, are just some smart-mouthed prick
who will never accomplish anything worthwhile in your miserable
piece of shit existence.
.
Wow! A defender of Jimmy Carter. Do you hate jews, too?
Which, of course, is exactly what they will be doing. Make the gas a plasma, and contain it with magnetic and electric fields.
Prediction for end of Universe #42: Fencepost error in Quantum_bogosort.cpp
Well, we know that the US had nuclear-armed B-52s and nuclear xommamd and control EC-135s airborne 24/7 until at least 1992. That led to a couple of scary accidents. Google "Chrome Dome" for more information. That was one leg of the nuclear triad - subs, missiles, and bombers on alert 24/7. The bombers periodically received a "do not attack" signal.
What the strategic command has been up to since 1992 we don't know. They keep such things secret when possible, for obvious reasons.
Space Balls had a lovely Winnebago that traveled through space quite fine thank you very much
Bloody moron.
Yet space does not have that much friction to fight against. So I would say it's a win.
The Saturn V employed a total mass of 2970 tonnes to lift a mere 118 tonnes to LEO. But the actual raw energy needed to lift 118 tonnes to 200 km is E=mgh = 118,000 times 9.81 times 200,000 = 232 GJ, which is the quantity of energy contained in just 5.47 tonnes of gasoline. So the efficiency of the Saturn V was 0.184%, not because it was a "bad" rocket, but because it was a rocket.
If you just lift the payload to 200 km, it will immediately start falling back to the surface. The payload must also be accelerated to orbital speed, 8000 m/s, at which the 118 tonnes has a kinetic energy of 3776 GJ, so your "efficiency" is off by quite a bit.
what we really need is a booster that uses a nuclear pulse engine. Then weight limitations sort of, well, there are no weight limits.
I'm sure Ted Cruz can comprehend nuclear thermal rocket engines, but making the big decisions for NASA, while avoiding cost overruns requires a lot of knowledge. That is something Ted Cruz will not take the time to do. Ted Cruz is focused on other areas. Hopefully he will not make any actual decisions on NASA...
The VASIMR is the likely candidate for inter planetary travel.
Think of adding a microwave to an Ion engine super heating the plasma first. . It's claimed to increase an Ion engine by 100x (Claimed).
http://en.wikipedia.org/wiki/V...
There is also a problem with launching a reactor into space, it not only breaks a few treaties, it's the possibility of it failing falling back to Earth; the reason sending very high level nuclear waste to the Sun isn't being considered.
In cars and trains, the fuel is not "reaction mass," it is just fuel. Planes do have reaction mass, provided by the air sucked and expelled by them. Rockets do not have an atmosphere around them in outer space.
The nuclear fuel we have on this planet is our entry-ticket for exploring and colonizing the solar system. The most stupid thing that can be done with it is using it to generate electricity, because that can be done in a number of other ways. At the same time, until fusion takes off (if ever...), fissionable material is irreplaceable and cannot be made artificially.
Most ACs are not even worth the keystrokes to insult them. Be generically insulted by this and ignored otherwise.
I didn't know Elon Musk was even selling cars in the 1940s and 1950s, when franchise laws were passed to prevent the two big bad corporations, GM and Ford, from competing unfairly with small dealerships.
Oh, did you think Tesla was the first car company who wanted to sell direct? You're off by about a hundred years.
> maximum final Delta V from source of circa 58,000 ft/sec
Einstein would like to have a word with you. That word is "relative". Suppose there is a planet traveling away from the earth at at 50,000 ft/sec. An alien on that planet can fire a rocket, which can travel away from that planet at 50,000 ft/s, meaning 100,000 ft/s relative to earth. As it catches up to another planet, it might photograph some other aliens launching their own rocket at 50,000 ft/s, which is 150,000 ft/s relative to earth.
In fact, the SAME rocket could from earth to the first planet, then be launched from that planet, then stop at the next planet and be launched at 50,000.
Come to think of it, stopping at each planet doesn't change anything. It's ALWAYS standing still relative to something, and can launch away from that something to 50,000 ft/s. The gas leaves nozzle at 58,000 RELATIVE TO THE COMBUSTION CHAMBER. In other words, it can always go 58,000 faster, as long as it can fire it's engine. 58,000 is the limit for a BALLISTIC projectile, one that is fired from a gun and doesn't carry a working engine with which to keep accelerating. The limit is 58,000 RELATIVE TO the chamber in which the gas is burned. By carrying the combustion chamber within the craft, it can accelerate until it approaches C.
And how else would you propose to move in space?
Maybe if we built a really tall ladder...
Dude, our tech tree is no where NEAR Ion Thrusters.
Honestly we're still in the Keep stage in Warcraft 2, we have yet to graduate to Starcraft.
How the fuck are you still able to post at a default score of two when you are both blatantly talking about things you don't begin to understand (looking at only the change in gravitational potential energy but not the change in kinetic energy, saying shit like "So the efficiency of the Saturn V was 0.184%, not because it was a "bad" rocket, but because it was a rocket.", etc.) and also accusing *other* people of being stupid? Nathanbp, among others, posted a very clear rebuttal to your bullshit, and you not only didn't address it you insulted them for it. Go learn even the basics of orbital mechanics, and the basics of rocketry (specific impulse, the rocket equation, what delta-V really means, etc.), then come back.
As of this writing and with the way I have my account set up (close to default), your original post is at -1, none of your others in the thread are at higher than your default level of +2, and people pointing out how utterly wrong you are have hit +5 at least twice. Your response to such well-reasoned line-by-line rebuttals as that of brambus is, I quote, "Bloody moron." To that, I can only say: yep, you really are.
There's no place I could be, since I've found Serenity...
You can't fix stupid.
You've certainly proved that.
No other mode of transportation has to carry its own reaction mass and throw it away. Not bicycles, cars, trains, ships, submarines, or airplanes.
Holy crap, I can't believe I just read that. Here's a hint as to why that's wrong:
(note that all of these also "throw away" excess heat)
Bicycle (and just walking, running, exercising, etc): Reaction mass (RM) - Food calories (no calories in, no energy out) water. Thrown away (TA): sweat, the dump you take when you get home.
Cars: RM: Gasoline TA: CO2, CO, and various other byproducts that exit the exhaust pipe.
Trains, ships, submarines, airplanes - see cars, fuels may vary but all use some form of fossil fuels that emit CO2, CO, etc, except maybe nuclear ships which generate nuclear waste that eventually needs to be 'thrown away' (or reprocessed with more vast amounts of energy use).
Oh, and maybe "electric vehicles" (cars/busses/trains) - except for the most part their "thrown away" comes out of coal/nuclear power plants... and eventually the batteries (temporary storage of the 'reaction mass' energy) need replacing.
>> , an NTP rocket could generate 200 kWt of power using a single kilogram of uranium for a period of 13 years
That is wrong. A single kilogramm of Uranium can not do much. The critcal mass is 56 kg.
And that's for a perfect sphere of highly enriched U235. With this configuration it's also a nuke bomb, not really an effective means of travel in one piece.
For a nuke reactor operating reasonably, you need 500 kg/ many tons of uranium.
And that's a risk to the whole mankind to put that in a rocket. A launch failure with a ton of fissile material would realistically kill everyone on earth.
That's the signe reason why this was not done in the first place.
aaaaaaa
That's exactly what it is. I think most people here realize that.
Well, until someone comes up with a workable theory for a reactionless drive, we're stuck with reaction mass. But that doesn't mean we're stuck with chemical rockets - if you could accelerate you reaction mass to some nontrivial fraction of the speed of light you wouldn't need very much of it.
We have ion thrusters since decades. Nearly every modern satellite uses them for station keeping.
Plenty of deep space probes used ion thrusters to reach their target.
Try to keep up with news or your next claim might be we had no plasma engines.
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
i know your parent has namedropped on you, but they also provided some substantive arguments. i'd be interested in reading your rebuttal of the actual points made in brambus' comment.
Not being up front about this seems intellectually dishonest. If you want to use this kind of nuclear energy is space for manned programs, you are advocating a risk vs. reward tradeoff. Don't sidestep the issue.
Here's the Wikipedia article about nuclear power in space.
Why is Snark Required?
Trams?
At some height (maybe 65,000 km), you do get to geo stationary orbit and if you have a space elevator, you wouldn't fall back down.
Anyways, I need one of these nuclear thermal generators or my electric car. The solar panels getting thermonuclear fusion power from the Sun aren't quite as efficient as this would be.
How many people are going to post here not knowing what a reaction mass is? It is not a source of energy, it is a source of momentum, the material that conserves momentum by going in the opposite direction when you increase the momentum in the direction you want.
A space elevator would swing around with the Earth, and its linear velocity would increase with your distance from the center of the Earth. This is why there is eventually a point where you velocity on a space elevator would match orbital velocity. If you just fire a rocket straight up, there is no increase in your horizontal velocity from that imparted by the rotation of the Earth. Even if launching from the equator, that speed wouldn't match orbital speed until about 1.8 million km from Earth, which would be outside Earth's Hill sphere.
Our physics if fucking wrong, and space drives are possible!
Instead of fucking with rockets, NASA needs to figure out what is wrong with our physics, and build the fucking space drive!
Houston, launch failed over the east coast and the plume form burn up on re-entry is drifting toward New York City...
Get ready for mass evacuation and the setting up of a 200 mile wide 600 mile long exclusion zone.
Congratulations, you've just described the internet.
No other mode of transportation has to carry its own reaction mass and throw it away. Not bicycles, cars, trains, ships, submarines, or airplanes.
Actually, jet airplanes do. A significant portion of their thrust comes from the mass of jet fuel, oxidized and ejected out the rear of the jet engine.
Second, every single mode of transportation has reaction mass. For modes that travel on ground, the Earth itself is the reaction mass. For airplanes, it's mostly pushing air. For boats, it's pushing water.
Finally, it makes no sense to talk about transportation modes that don't go where you want them to go. Rockets are horribly inefficient in comparison to cars, but cars can't drive to space. While there are ideas, such as the space tether for making a genuine road to space, they rely on having enough economic activity from Earth to space to make them viable. That market has to be created by a less efficient mode of transportation first.
Even then, space tethers and similar systems need some sort of reaction mass to keep the system from getting pulled down over time by all the payloads coming up. But that need not be provided by a high thrust chemical engine.
Looking at the anti-nuclear comments, you can only admire what an amazingly effective job KGB&Co did at spreading anti-nuclear FUD in the 70ies and 80ies! Unfortunately for the green folks and the rest of humanity, there won't be any progress with getting rid of carbon based fuels and global warming until they get over their neurotic, nuclear hang ups and realize how far we have come, and how safe and useful it could be today. Imagine if they had built that rocket, and a manned mission had been on Mars in the 80ies! What would our world have looked like today?
A significant portion of their thrust comes from the mass of jet fuel, oxidized and ejected out the rear of the jet engine.
The typical fuel to air mass ratio of jet engines is a couple percent, and at highest at the stoichiometric ratio of about 6%. This is small enough that it gets rounded down to zero in a lot of calculations. For something like a turbofan, it is even more air.
Second, every single mode of transportation has reaction mass. For modes that travel on ground, the Earth itself is the reaction mass. For airplanes, it's mostly pushing air. For boats, it's pushing water.
Reread what you quoted:
No other mode of transportation has to carry its own reaction mass and throw it away. Not bicycles, cars, trains, ships, submarines, or airplanes.
There was no implication that momentum was not being conserved.
Even then, space tethers and similar systems need some sort of reaction mass to keep the system from getting pulled down over time by all the payloads coming up.
You can change the length of a tether to balance forces of things going up and down, to remove the need for engines to provide that force and resorting back to using the Earth as a reaction mass essentially.
"NASA Looking At Nuclear Thermal Rockets To Explode the Solar System"
aaaaaaa
This shares the fundamental flaw of all rocket technology: the fact that any rocket has to carry and throw away a vast load of reaction mass... Not bicycles, cars, trains, ships, submarines, or airplanes.
Not sure if you are ignorant of physics, or indirectly clamoring for space elevator/railgun-esque space access. Either way - you have to use reaction mass at some point, because even if you have enough delta-v from another means you need to be able to maneuver in space, circularize your orbit, etc. Also, rockets are the only way anybody has ever gotten to space, ever, and for the foreseeable future they will continue to be our primary means of access.
what could POSSIBLY go wrong?! ;)
The article makes an arugment that the closed-cycle gaseous "lightbulb" design is the best option. They even have a freakin' picture of it, FFS! All parent had to do is scan the images, and would have avoided wasting our time with a red herring argument.
"Politicians and diapers must be changed often, and for the same reason."
The typical fuel to air mass ratio of jet engines is a couple percent, and at highest at the stoichiometric ratio of about 6%. This is small enough that it gets rounded down to zero in a lot of calculations. For something like a turbofan, it is even more air.
Sounds significant to me. Not really sure what the point of most of the rest of your post was since I didn't imply that the original AC's observation was physically incorrect.
You can change the length of a tether to balance forces of things going up and down, to remove the need for engines to provide that force and resorting back to using the Earth as a reaction mass essentially.
I'll have to think about that.
The good news in all this, is that not only does O want America to go to Mars, BUT, he backs nuclear engines and power. Sadly, the dems fight it. But, the current CONgress is likely to be pro-nukes, which I doubt that O will stop.
I prefer the "u" in honour as it seems to be missing these days.
Solar-Thermal gets the same performance as Nuclear-Thermal, except the reactor is 150 million km or more away. Both heat hydrogen gas to high temperatures, and therefore get the same exhaust velocity. Large solar concentrators are lightweight, and not hard to build in orbit. One the size of the Space Station (100 meter diameter) would generate 10 MW.
The nice thing about solar-thermal is it avoids all the issues with nuclear-anything. No Greenpeace protestors, no extra costs for nuclear security on the ground, radiation shielding, etc.
The "really tall ladder" still only gets you so far. Once you're at LEO, you're still only halfway to anywhere
Concentrated solar thermal gets much better performance than nuclear thermal because you're only limited by the materials properties of your heat exchanger, not your reactor fuel. The problem with solar thermal is three fold.
First, you have to be able to see the sun, so your burns are restricted to times where you're not in Earth's shadow. That could make transfer windows difficult to hit, of course if you have a thousand seconds or higher ISP, that's not such an issue.
Second, we're talking about high thrust rockets so you don't have astronauts sitting in the radiation belts for days as a low thrust rocket spirals out. That means you're going to have to have significant structure to support that concentrator, and it's no longer going to be very lightweight. Of course with such a high ISP, this may no longer be such an issue.
Third, this reflector cannot simply be static. It needs to be able to articulate to whatever angle you need to thrust, which greatly increases the complexity and mass of such a system.
First, nuclear fuel is extremely dense and tends to be the think OTHER things get broken by in any collision between to objects.
Second, nuclear fuel does not "burn" in the conventional combuston sense; the burning fuel from a rocket sxplosion would not ignite the nuclear fuel and cause it to "burn" (as-in burning wood or burning kerosene).
Third: Using a large rocket, like the SLS NASA is currently building or even the Falcon9 Heavy that SpaceX is building, one would launch the nuclear engine in an UN-FUELLED state (if it crashed, it would just be like any other non-toxic and not-radioactive metal debris). The fuel would go up on the same or another rocket BUT it would be in an unmanned version of the otherwise manned capsule (like an unmanned Dragon or Orion) complete with a man-rated launch abort system ... therefore in any launch vehicle failure, the radioactive core would be pulled away by an abort rocket and would then safely parachute back to earth in the safety of a capsule that could easily be recovered by the navy (just the same as any humans recovered in a manned version). The Americans and the Russians have launched MANY nuclear reactors into space over the decades (most were RTGs like the ones on Voagers and Lunar Modules) even without using LAS-equipped capsules and yet the scenario you chicken-little about has never happened.
Sounds significant to me
Being small enough to be equated to zero to simplify the math is the opposite of significant in engineering and physics.
Being small enough to be equated to zero to simplify the math is the opposite of significant in engineering and physics.
Only if your equation is relevant to the discussion. It is not.
Being small enough to be equated to zero to simplify the math is the opposite of significant in engineering and physics.
And I'll point out that the 2-6% contribution to thrust matters to actual fuel consumption, which a major part of the original subject (recall the discussion of "efficiency" which was somehow meant to discredit chemical rockets).
Fun Facts : Coal is 1,000 to 10,000 more dangerous per unit energy than nuclear. Even taking the worst case figures from Chernobyl (50,000 dead) we would actually need a Chernobyl about every two weeks for nuclear to be as dangerous as coal. :D
Fun Facts : Because of the above & the anti-nuclear campaign CND and Greenpiece have themselves killed roughly 5 to 10 million people.
That means that nuclear protesters have so far killed at least 10 to 20 times the number of people killed by nuclear weapons.
Below the speed of light Special Relativity is one of the most accurate theories in physics - above the speed of light..
I'll take "what is a solar sail" for 500, Alex.
http://en.wikipedia.org/wiki/E...
What exactly has osc developed that helps anybody?
credit should go to those that do real things. Osc is worthless.
I prefer the "u" in honour as it seems to be missing these days.
The poster you are replying to is a moron.
Bicycles, cars, and trains can push against the ground using friction assisted by gravity to propel themselves.
Ships and submarines can gather and push water to move themselves through the water.
Airplanes can gather and push air to move themselves through the air.
Rockets can gather and push... vacuum to move themselves through vacuum? No. Vacuum has no such properties to push or propel. Essentially, you have to take something up with you to throw out the back end of the rocket in order to move forwards as there is no surface to push against or material to gather and throw out the back end.
I am not telling you anything you do not know. Just saying for the benefit of the PP.
"Someone needs to talk to the tree of liberty about its ghoulish drinking problem." by ohnocitizen
You may be doing the arithmetic right, but you're starting with the wrong value of V. V is the velocity of the exhaust gas relative to the rocket, not relative to some arbitrarily chosen planet, such as earth.
Let me put it this way for you.
Suppose Puke Skyrunner is walking around the starship. He walks over to a rocket-powered X-wing that's parked inside the starship. At what velocity can the X-wing fly away from the starship?
Here's one answer that's clearly wrong:
It depends which planet the X-wing was built on.
That's clearly wrong, agreed? Yet that's actually what you're claiming, as I'll explain.
Let's have a look at this:
Suppose that the maximum speed of the X-wing per the gas velocity is Z.
Skyrunner can fly out and fly away from the starship at Z, right?
Suppose the starship happens to be flying past earth at 0.8*Z.
Skyrunner flys the X-wing out of the starship at Z, so people on earth see the X-wing as going 1.8Z.
Still identical physics:
Skyrunner fly's the X-wing bdrom earth to the starship, which is still passing earth at 0.8Z.
The X-wing catches up to the starship and parks inside.
Two years later, Puke Skyrunner gets in the X-wing.
Clearly, the velocity Puke can fly doesn't have anything at all to do with the velocity the craft had flown 2 years ago. Rather, it's governed by the exhaust gas velocity.
Agreed?
Maybe he can still fly away from the starship at Z?
The physics of this scenario are identical:
The X-wing flies from earth to the starship, at 0.8Z
The X-wing parks NEXT to the starship, rather than IN the starship.
Puke Skyrunner reaches out the window and touches the starship, then flies away.
Clearly, the max speed at which he can fly away doesn't depend on how long he spends at the starship.
Whether he spends 2 years living in the starship, or 2 seconds touching the starship, he can fly away at Z.
Note that Z (relative to the starship) is still 1.8Z relative to earth. So people on earth still see the X-wing as traveling 1.8Z.
Still identical physics:
Skyrunner catches up to the starship, which is going 0.8Z, but doesn't touch it.
Skyrunner flies away. Still the people in the starship see him fly away at Z.
People on earth still see that as 1.8Z, nothing has changed.
Still identical:
Skyrunner goes 0.8Z to catch up to a starship that he's only imagining, that doesn't exist.
Skyrunner flies away. Still at Z.
People on earth still see that as 1.8Z, nothing has changed.
Still identical:
Skyrunner doesn't imagine a starship.
He flies away at Z.
People on earth still see that as 1.8Z, nothing has changed.
Why? Because he can always accelerate up to the velocity that the gas is leaving the NOZZLE. The key number is the velocity of the gas AS MEASURED FROM INSIDE THE ROCKET. Whether or not earth happens to be going by at a million miles per hour doesn't matter.
Kirk Sorensen is one of the few people I know that both worked at a space agency (NASA) and in the terrestrial nuclear power industry (Flibe energy, Teledyne Brown Engineering), says this is a fools errand. While NTR rockets could offer high ISP, they will weight wayyyy too much (too low thrust to weight). Plus nuclear reactors can't be scaled down like other rocket engines.
We looked into all deep space propulsion technologies.
Until we have a fairly lightweight nuclear reactor, it's unlikely this will fly (pun intended).
At the very least the nuclear rocket would have to have its final assembly in space, and would consume a lot of monster LEO launches to bring the components up (billions in launch costs even using the cheapest rocket to become available, the Falcon Heavy).