Re: Project Orion Reborn.


Posted by Pasti on Feb 10, 2004 at 00:05
(67.69.240.132)

Re: Project Orion Reborn. (Wayne Smith)

"You are right that we cannot just produce one huge blast and send the cargo into space. You might be surprised at the number of anti-Orion people I speak to who actually assume that Jules Verne style launching and then go into a long tirade about why it won't work."

I am surprised they even read Jules Verne's "From Earth to the Moon".

"Clearly you are capable of rational thought. Therefore I will ignore your opinions and concentrate on your "facts"."

Thank you Massa.

"It was a common "fact" that explosives could only be used to blow things up. Everyone from Generals down assumed this to be the case so nobody took Orion seriously. They needed a simple model test to demonstrate to the high brass that the principle of detonation propulsion worked. That was the only purpose of the model and it was a total success."

I am not surprised by the level of imbecility at brass level.I could quote several jokes on that issue, but it would be to no practical avail.
However,it shows (at least some)sloppiness from the the part of the PI involved in the project too.The best example was and still is the traditional cannon,when it comes to propulsion by detonation.

The bulk of the research was concentrated on materials testing. How plasma and close proximity atomic blasts react various metals and shapes. Pioneering work.

Well,you might say that it was pioneer work, but I am still skeptical.As much as I have been able to learn about this project, they tested matrials more for chemical detonation errosion,for dynamite charges.And this plasma is orders of magnitude colder than fission plasma, not to mention fusion plasma.And it also lasts much less than any of the latter two.So this testing, while good of the dynamite charge detonation propulsion, is pretty irrelevant for nuclear detonations.

"Only for a small ship. For a large one we can use hydrogen bombs. A thousand times cleaner relative to yield than small fission bombs. Bigger bombs are far more efficient."

That is an entirely different story.The project originally proposed fission bombs,and for the small 10000 ton ship, there was a 10kton blast every second at liftoff, while at high altitude they got off with 20kton every 30 seconds.Which is a lot of fallout.

If you want to use H-bombs, forget about them being "clean bombs".Indeed, fallout is much smaller, but X-ray and gamma ray radiation becomes huge.And the plasma temperature is much larger,and lasts longer.

"I'm talking about one launch. Already that brings the 1% down 0.1% at a conservative guess. By eliminating a big groundburst with a wide steel launchpad we also eliminate 99.999%(conservative estimate, probably higher) of that 0.1% leaving 0.00001% only. One coal plant probably pumps out that much in a day."

I am very tempted to smile at your estimates.First of all, you have to do testing, you cannot just build something and pray to God or whoever that it will work at hte first shot.That would really be both idiotic and scientifically sloppy.There are several other things that have to be tested, not only the propulsion system.The entire thing as a whole must work reliably and safely, otherwise you pretty much condemn the crew to a more or less faster death.
So you have to do testing, you cannot get rid of it.
Secondly, if the ship is large, as you would like,you need more and more powerful explosions the heavier the ship.And the steel you mention won't help at all with the elmg radiation from a fission bomb.It won't help with a fission bomb either, unless you build a huge "filter" that releases pressure while keeping radioactive material inside.Useless to say, such thing does not exist, and I don't even think it couls be built at the scale you want.

"They won't be anything like Fat Man and Little Boy because those were fission devices. Hydrogen bombs are equivalent to a thousand of those and only create a thousandth of the fallout."

In this case the steel ground pad is useless, X-rays go through steel almost without absorption.In the best case you will only vaporize portions of the pad, releasing iron ad whatever else components in the air.

"In a large Orion there is enough shielding from the structure alone to protect the crew. You need about 60cm ideally. For a very small Orion it becomes a problem and does indeed cost you in payload but this doesn't apply to a larger model. No lead."

Huh? You must be joking Mr.Feynman!60 cm of what?Do you actually know what 60 cm of steel means for a plate? There is a limiting size after which the thing will mecanically crumble unger gravity(For comparison reasons,oil tankers have a few inches thick skin).
Have you checked the cross-sections of X-rays into steel?Or for gamma rays?And the screening factor of the structure?
Think like this:the bigger the ship, the heavier, the heavier, the more power you need from the blasts, the more power you need, the higher the elmg output, and hence, the thicker the screen must be.
Lead has (still) the larger coss-section for X-rays and gamma rays,so it is the most efficient to use in terms of thickness,and in terms of weight.And even for a large ship, the screenening will eat a huge amount of payload.

"I beg to differ. Even plain old Aluminum performed very well in nuclear tests."

Under how many tests exactly?Remember that it has to survive (almost intact) to several detonations to say the least.Several meaning at least ten!

"Steel was the material of choice and tests were performed with objects placed within 3 metres of a nuclear blast. The best shape is a round plate that's thickest in the middle but tapering towards the edges."

This is the crap I was talking about in the last post.They rediscovered this shape (BTW it is also concave, with the concavity towards the blast), which was already known from penetrating anti-tank charges.Good work, what can I say.

"Ablation was a key issue of the research program (not the 'hot rod'). It was discovered that graphite based oil has peculiar opaquing properties and could be used to virtually eliminate surface wear entirely. An ingenious method was found to spray a coat onto the plate between detonations."

This was for chemical blasts, not nuclear blasts.At the fision/fusion plasma temperature,you have more than ablation. You have surface melting,induced stresses, fatigue,induced radioactivity.They never accounted for the latter,in a reliable way.

"Theodore Taylor?"

I think it was Everett,or something similar

"He did. In his notes about early single shot tests he states that many, many times. As I have already said, it was only built to demonstrate that explosives can propel a rocket."

As I said,a cannon would have sufficed, if the PI in the project had more alert brains.No offense to them intended, but it is the truth.

"Something the administration couldn't comprehend. They didn't believe it was possible. Most of them still thought rockets moved by pushing against the air."

Well,I am quite familiar with the opaqueness of admin.But they were scientists,they should have done better.

"You are way, way off track again. I think 10,000 dollars was spent on that 'Putt Putt' after it was approved for construction. It went from drawing board to finished model in something like 6 months. No similarity to any military shells I'm afraid."

You have no idea what I am talking about, do you? It is the pusher plate, or whatever the name.The plate against which the pressure of the explosion pushed. It took hem a year and some until they arrived to the shape you mention above, round, concave and thicker in the middle.This is exactly the principle of the penetrating charge, used in WWII,almost 15 years ago.They did very good work, by Jove!

"Dyson only worked on the project a year. He wasn't even there when they built the successful launch model."

He lobbyed for it for years, together with daddy-o Wheeler, if I am not wrong, up to the point that they would not make committee recommendations regarding the effects of radiation/radioactivity from nuclear explosions because the project would end.

"He was one member of a large team which included theoreticians, experimentalists and engineers.Everybody just dug in and did a bit of everything. There were no guidelines for constructing an Orion so they just had to do it. As a consequence they were completely successful."

Uh, I am afraid I won't fell for this.In translation, what you said above reads:"They had no clue what they were doing, so whatever they did was a success."
Yeah, right.They reinvented the cannon without a muzzle, at a 7 million dollar tag, which indeed is a big achievement.J.T.Mason did better, and Verne was just a writer.

"The only failure in this story was the failure of Nasa to support it. As a consequence we now have a flag on the moon and nobody has been back there in well over 30 years. We could have gone to Pluto."

As opposed to what?Several other millions spent and several other crews fried to crisp?

Look,you are a fan, supporter of the Orion project, or its new(er)versions, the Daedalus and Prometheus I think they are called. Which is fine.But if you want interstellar travel, you will have to give up the mentality of extreme conditions, extreme circumstances, and extreme methods.
A flag on Pluto is useless if Pluto cannot be reached in a regular manner, on a regular basis.So is the flag on the Moon.It is only a symbol of pride,and nothing else. Not even of technical advance, if you think of the primitivism of the ship that landed on the Moon.
Of course, it proved a point,but unfortunately it never went further than that.

Instead of focusing on reaching Pluto, Mars, and whatever just to pin a flag on it, think of how to develop interplanetry travel as a continuous means of travel and exploring.A few men on a planet is hardly exploring, and a ship blasting its way across space is not the solution.In my opinion at least.




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