Thinking Clearly About Space

[dobbins]

I think that nuclear powered RLVs can be a solution to the problem of high launch costs, but only if they don't release radioactive byproducts into the environment. I'm not some knee-jerk eco-fanatic, but even I think that leaving a radioactive debris trial in the atmosphere is far too high a price to pay for access to space.<br /><br />A Nuclear rocket is a simple design just pump propellant through a reactor to heat it up. Not Hydrogen like some propose because that creates an explosion hazard at the launch site for some time after take off, just plain old water as the propellant here in the atmosphere. In space the propellant can be whatever substance is handy, hydrogen, water, methane, whatever happens to be the easiest to get a hold of for the mission profile.<br /><br />This does have some technical problems that need to be solved, so it isn't a short term solution. It also has some political problems because if you even mention the word "nuclear" it brings the Luddites crawling out of the woodwork.<br /><br />

 

[nyarlathotep]

Relatively speaking, compared to the hundreds of stratospheric fission tests in the 60's, a few hundred small hydrogen bombs in the kiloton range from a launch arent going to create a whole lot of fallout. Certainly not when compared to the amount of thorium, uranium and their decay products that the world is putting into the air each and every day burning coal. Provided you have a big steel launchpad, you shouldnt get too much local fallout. The ground is already irradiated anyway, thanks to the Brits. <br /><br />I agree though that the EMP and an ionisation cloud in the upper atmosphere is probably going to make a few satellite owners 'rather unhappy' for a couple of years.

 

[dobbins]

You need to recheck your figures. The smaller orbital version of Orion used 500 Hiroshima type bombs. The larger super size version used over a thousand fusion bombs. That is more blasts in just one launch than the USA and the USSR did in atmospheric tests from 1945 to the partial test ban treaty in 1963.<br /><br />The concept is so bad that other nations would be more than justified in launching a preemptive war against any nation that attempted to launch a single Orion starship from the Earth's surface, much less a series of them.<br /><br />

 

[syndroma]

> <i>A Nuclear rocket is a simple design just pump propellant through a reactor to heat it up. Not Hydrogen like some propose because that creates an explosion hazard at the launch site for some time after take off, just plain old water as the propellant here in the atmosphere. In space the propellant can be whatever substance is handy, hydrogen, water, methane, whatever happens to be the easiest to get a hold of for the mission profile.</i><br /><br />AFAIK, only hydrogen gives you Isp = 900sec, all other propellants are much less efficient and usually not worth the expense.

 

[dobbins]

Hydrogen gas plus Earth's atmosphere equals an explosive mixture. Having the launch area subject to exploding for a period of time after the launch is not a good idea. You need non-explosive water for launch from Earth's surface even if it does have a lower ISP.<br /><br />As for other uses the goal is cheap, not just the best ISP figure. If you have a ready source of methane and it's cheaper to use it than to extract the hydrogen, dispose of the excess carbon, and store the hydrogen for later use, then the methane is the better choice.<br /><br />We aren't going to get CATS if we don't drop the Ferrari mindset of whatever has the highest performance and go with whatever gets the job done at the lowest cost.<br /><br />

 

[nyarlathotep]

>>"Hydrogen gas plus Earth's atmosphere equals an explosive mixture. Having the launch area subject to exploding for a period of time after the launch is not a good idea."<br /><br />I dont really see why exploding hydrogen is a problem. Just design the rocket to be launched at sea.

 

[cuddlyrocket]

Launching at sea is a lot more expensive than launching on land.

 

[quasar2]

this is for all. one of the main reasons we`re frustrated is all the past plans have apparently failed. <div class="Discussion_UserSignature"> </div>

 

[josh_simonson]

So what can be done to help 'elasticize' the demand curve for launches? Tourism certainly has an elastic curve, but weather, gps, telco and imagery satelites aren't very elastic at all since the satelite costs as much or more than the launch does, and those markets are already nearing saturation. <br /><br />There's probably room for improvement in the funeral services area, certainly it'd be nicer to get ALL your ashes to the moon or wherever, and more exotic packages are possible, such as sending your ash and a sample of your DNA beyond the solar system - opening the possibility that aliens could find it and clone you. That'd make an amusing fantasy for dying rich folk to be the first human *cough*DNA*cough* to go to alpha centauri...

 

[henryhallam]

<font color="yellow"> That'd make an amusing fantasy for dying rich folk to be the first human *cough*DNA*cough* to go to alpha centauri...</font><br />I would think that it would probably take them so long to get there that somebody launched in 500 years' time on a fusion rocket or something would beat them to it.

 

[josh_simonson]

Not like they're going to complain though, being dead and all. <img src="/images/icons/wink.gif" />

 

[gunsandrockets]

"You need to recheck your figures. The smaller orbital version of Orion used 500 Hiroshima type bombs. The larger super size version used over a thousand fusion bombs. That is more blasts in just one launch than the USA and the USSR did in atmospheric tests from 1945 to the partial test ban treaty in 1963."<br /><br />There is no "orbital version" of Orion. The small 4000 ton version of Orion was predicted to have a payload of 800 tons to Mars orbit plus return to Earth orbit. And the 'bombs' used were not Hiroshima bomb power of 15 kilotons. When launched from Earth the 4000 ton Orion would have used 0.5 kiloton pulse units in the atmosphere and then 5 kiloton pulse units in space.<br /><br />As for atmospheric fallout, compare the puny 0.5 kiloton pulse units to the atmospheric H-bomb tests of the past. The Soviets even detonated one 50 megaton bomb in the atmosphere, which is one hundred thousand times the power of the small Orion pulse unit.

 

[dobbins]

/* ad hominem deleted */<br /><br />Go research the history of the project.<br /><br />

 

[gunsandrockets]

"Go research the history of the project."<br /><br />Research? Oh you mean like the book "Project Orion" by George Dyson? The one on my bookshelf? The one I quoted from for the information in my post? That one?<br /><br />heh<br /><br />What's your source dobster? <br />

 

[dobbins]

Try looking at reviews by practical people that didn't have an emotional involvement in Orion.<br /><br />

 

[josh_simonson]

Hydrogen bombs don't produce as much fallout/kiloton as fission bombs do. Most of the energy comes from fusion, which is relatively clean. Orion would require fission bombs, and so would be extremely dirty. <br /><br />Also, some percentage of the bomblets would be duds - presenting an unacceptable proliferation risk if they're randomly falling all over the world.

 

[gunsandrockets]

"Hydrogen bombs don't produce as much fallout/kiloton as fission bombs do. Most of the energy comes from fusion, which is relatively clean. Orion would require fission bombs, and so would be extremely dirty."<br /><br />Extremely dirty relative to what? In actuallity the tiny in-atmosphere Orion pulse units leave a small amount of fallout in relation to previous atmospheric bomb testing.<br /><br />All H-bombs use a fission explosive as the primary detonation. Many H-bombs even use a fission explosive as the tertiary detonation to increase the total bomb yield.<br /><br />Even the cleanest H-bombs leave quite a bit of fallout from the primary fission explosion. A good example is the 50 megaton 'Tsar bomba'. It was one of the cleanest ever bombs. Only 1.5 megatons of it's 50 megaton yield came from the primary fission explosive. Even so that is still 3,000 times more fission from that one bomb than from one of the tiny 0.5 kiloton Orion pulse units.<br /><br />http://nuclearweaponarchive.org/Russia/TsarBomba.html<br /><br /><br />

 

[dobbins]

Trying to wish away the fallout that WILL be produced isn't going to make it vanish.<br /><br />Though I do find it amusing that you would pick a thread that is devoted to taking a realistic look at space to try to push one of the most unrealistic projects around. Orion is illegal, it violates international treaties. Orion is politically impossible, there isn't even the remotest chance that any government will undertake it and there certainly isn't a chance that a government will allow private interests to develop their own nuclear devices.<br /><br />

 

[gunsandrockets]

"Trying to wish away the fallout that WILL be produced isn't going to make it vanish."<br /><br />Nope. I'm not trying to 'wish away the fallout'. I'm only trying to accurately portray the amount of fallout so discussion of real risk could take place. As opposed to your exaggerations of the amount of fallout Orion would generate.

 

[dobbins]

Let's see, I stated 500 Hiroshima type bombs, that means fission devices, the only kind that existed at the start of the project in 1947, and the type that would be used for the early smaller design. The later flying city fusion bomb designs give a whole new meaning to the term unrealistic.<br /><br />It isn't going to happen. period. end of story.<br /><br />

 

[j05h]

>... Orion is illegal...<br /><br />The thread was "thinking clearly about space". Orion is a great idea and simply not implementable. <br /><br />Thoughts: we need a company that can build an American equivalent of the FGB. We need a business case for water mining at one of several locations off-Earth. We need the rocket racing league to succeed. Most of all we need people in orbit to provide services to, and products in orbit to sell them. And beamed power.<br /><br />Not "clear" thinking maybe (it's 1AM), but cogent ideas on how to bring about space settlement and development. Orion, my eye. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[danwoodard]

I am glad to see some discussion of realities. I joined L-5 in 1976 and have worked for a space contractor for 16 years. I have spent most of my life trying to build support for space. <br /><br />Unfortunately the VSE is unrealistic. There is really only funding for eight lunar landings, none to prepare for a Mars flight or suppport a permanent Lunar base. All that is left to future administrations, and McCain or Clinton will have to deal with a huge deficit. VSE will slip and eventually be dropped back to support of the ISS, which can be justified by "international obligations". <br /><br />We need to admit what we all know; that the cost of manned spaceflight with 1960's technology is far to expensive to be practical. Our first task should be to develop the technology that can reduce this cost. This is harder than just repeating Apollo, but it would give us something of lasting value. <br /><br />We tried to do this with the Shuttle. Obviously it missed its cost goal by a factor of about 100, mainly because we had no prototypes, and thus no flight experience with many of the critical systems. Physics don't lie. There's no real need for nuclear propulsion for the Earth-to-LEO portion of a flight because the cost of the fuel is minimal; the money is all spent in construction, maintenance and repair. The only reason the Shuttle is so expensive is because it was our first design, and we made numerous mistakes. <br /><br />The cancellation of the reusable launch vehicle technology demonstrator programs was a mistake. If private industry can make human spaceflight safe and cheap then NASA should be assisting that private industry. The cancellation of hundreds of small research programs to fund VSE was a mistake. The gutting of the aeronautics programs was a mistake; they provide more practical benefit than manned spaceflight simply because the number of air travellers exceeds the number of space travellers by a factor of roughly 1,000,000 to 1. Does anyone know

 

[dobbins]

An RLV is not economically viable without a higher launch rate than anything NASA will be doing for some time. Economic realities can't be overcome any more than the laws of physics can. A 747 that had the kind of flight rates that a RLV will have in the next decade wouldn't be economically viable.<br /><br />You can't have an RLV without a center to service it. A service center has to be staffed, and you can't just call the labor agency and hire techs when you need them. You have to a certain number regardless of what flight rate you have. This is why is costs almost as much money to fly zero Shuttle missions in a year as it costs to fly a half dozen missions.<br /><br />The ESAS recognizes this economic reality. If reusing the capsule proves to be viable, it will be reused. If reusing the solid boosters proves to be viable they will be reused. It isn't 1960s technology anymore than an aircraft with wings is 1903 technology or a modern automobile is Model T technology. The laws of physics haven't changed in the past 40 years. A basic shape that was found to work best in 1965 will still work best in 2012.<br /><br />

 

[gunsandrockets]

"Let's see, I stated 500 Hiroshima type bombs, that means fission devices, the only kind that existed at the start of the project in 1947, and the type that would be used for the early smaller design."<br /><br />As I pointed out previously your description is an exaggeration. The in-atmosphere pulse units of the Orion would have had a yield of 0.5 kilotons, a tiny fraction of the size of a "Hiroshima type bomb". Yet here you go again merrily repeating yourself, evidence be damned. Shameless and amazing.<br /><br />

 

[dobbins]

ROFL,<br /><br />There weren't any 0.5 kiloton bombs at the time Orion came into existence, there were only the designs used at Hiroshima and Nagasaki, and the Hiroshima design had the lower yield of the two.<br /><br />Either way the design is illegal, and politically impossible which places it in the same realm as warp drive spaceships. Are you ever going to get realistic, or are you going to continue to split hairs over fantasy designs?<br /><br />