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who will be the first?

Posted by: p1c3rd - Sat Apr 16, 2005 12:52 pm
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who will be the first? 
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Post who will be the first?   Posted on: Sat Apr 16, 2005 12:52 pm
Who will be the first to create a stable fusion reaction to power a suitable impulse engine. I've been working on the problem for about two years. It seems to me that trying to recreate the sun's surface temperature of 10,000,000 degrees celsius, is not viable at this time, so what other options are there? Sonoluminescence? would this work? Probably not having recreated the experiment several times myself. So where does that leave us? In short, one brilliant mind away from achieving it. I certainly am not that person. However, having studied the principles of Impulse driven engines I guess that it can be achieved using fission reaction instead of fusion reaction. The energy from the reactor(either plasma or steam) Could be used to push and retract the impulse engines at a suitable rate. Anyone can build an impulse engine from a spring and some bolts. (just put "impulse engines" Into google) I don't think man will progress very far into deep space without A)Artificial gravity B)Fusion based power source.


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Post    Posted on: Sat Apr 16, 2005 1:52 pm
Any type of engine that produces emissions uses fuel, so, regardless of how efficient it is, unless a vehicle can gather fuel during a voyage, it'll run out eventually because it's fuel source is finite.

So for long range voyaging, it seems to me that the better solution is to figure out what you can gather as you move through space to use as fuel, then design the systems to use that fuel regardless of how efficient that may be compared to what other propulsion systems are available. Since for longer voyages the speed of the vehicle will hopefully be fairly high, impacting molecules while traveling in the "void" of space will be at higher rates so this may not be as impractical as it sounds.

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Post    Posted on: Sat Apr 16, 2005 3:03 pm
Nucleon fusion is still far away. And it's a government project. Europe is still planning to build a next testreactor for this, for 10 billion euro i think. But as long as they talk about what, where and why, it's not gonna be in our lifetimes.

Nuclear reactors is probably the most efficient energy source for long-time voyages. The radioactive waste is not a concern for space, since it barely adds to the allready present background radiation. Only problem and concern is to get it into space. If something happens in the earths atmosphere, we got a big problem.

For gravity, i don't see the problem. With a rotating 'donut' you can get failry easy 1g. If you want 1g, you'll need a 'donut' with a radius of about 900 meters. It sounds big, but ISS is big as well, so it would only need a major amount of launches before it can be constructed. Several engineering problems need to be solved also, but since no one is actually working on such a concept, it's to bad to see it to go to waste. This is the most simplest way to get gravity and we can construct this now.


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Post    Posted on: Sun Apr 17, 2005 4:00 pm
The german astronaut Ulrich Walter has written a book titled "Au├čerirdische und Astronauten" - I translate it as "Aliens and Astronauts".

In that book he explains that a normal fusino drive using Bussard collectors wouldn't work because of the extrem thin distribution of Protons on space - inside the inner solar system as well as outside the solar system.

But there is one technology already experimented and tested that would work and could a space vehilce speed up to 0,12 c at least. There have been two concepts using this technology - rion and Daedalus.

The concept is a modified fusion drive - not fusion like the solar fusion processes but fusion bombs. Not those known for use in war but miniaturized ones - too small to be of use in any war. Theses bombs would be thrown out of the vehicle backwards and then ignited by laser. The detonaton would cause pieces of the bombs accelerated to the direction of the space vehicle which has a magnetic shield at its backside. The pieces of the bombs would impact that shield and cause impulses this way - fusion impulse drive. 100 detonations per second would be done to accelerate.

The concept has been tested by using conventional bombs instead of fusion bombs or nuclear bombs. The vehicle tested has been called "Put-Put" - and the tests have been conducted in the early 1960s. The results have been very convincing - there are photos in Walters book.

The problem with that drive has been a political one only - a UN tretay forbidding the use of fusuion bombs in space. If that problem wouldn't have been there an unmanned vehicle using that concept would have arrived at Barnard's Star or another star (I would have to look into Walter's book) in the 1990s or this decade already.



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Post    Posted on: Sun Apr 17, 2005 4:13 pm
That method has been somehwat discussed in the various discovery 'documentaries'. They use a huge 'parachute'.

If it would work, how would you 'brake'? Off course, the opposite is possible, but you would need as much 'bombs' to stop the ship as it takes to propel it to that speed. And you would carry all these 'bombs' with you. It doesn't sound very practical to me. 100 detonations per second, i hope not for very long because you would need a giant cargo ship just to carry the bombs.

I don't think very highly of these 'solutions'. It doesnt help us at all right now. If we would continue to work and think about the problems of tomorrow, we're getting no where fast. I know the sentence "if you cant travel fast, better stay home", and i might agree if you talk about interstellar trips, but we can do (imo) better things right now. Developement on futurethings will be slow anyway unless they are needed on a short term.

About fusion on earth, it's a fact that's still far away, and to get practical implication for other things then a fusion plant will be a long time after that.


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Post    Posted on: Sun Apr 17, 2005 5:14 pm
The bombs would be extremely small compared to the military ones - I will look into Walter's book if I find numbers. But they would be that smmall that vthey never could be compared to the existing ones - recall: 100 detonations per second!!! That cannot be of normal size.



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Post    Posted on: Sun Apr 17, 2005 5:31 pm
They have to be, but if they are that small that they can easily be stored, how big is the explosion? Wouldn't be the same impact as an ion drive?


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Post    Posted on: Sun Apr 17, 2005 7:48 pm
I agree that controlled, sustainable fusion is still too far away to make a prediction. Especially by a bunch of laymen on a net discussion board! :wink: As for externally pulsed plasma propulsion, that should work, at least according to a bunch of people who know more about it than I do.

Ekkehard: I believe it is only the Daedalus that would use 100 detonations per second. It would have the advantage of using pure fusion explosives, and thus would be cleaner, but it was the configuration of the explosives that made them impractical as weapons. something about needing the laser to detonate them. Unfortunately, it needs Internally confined fusion in order to work, which we don't know how to do yet.
Orion, on the other hand, uses currently available atomic weapons, and does not require scientific breakthroughs. There are many different configurations of this craft, and size of bombs depend on the size of the craft, and phase of the mission. I have seen figures for a 5000 to 10000 ton Orion firing 0.1 kiloton explosives, only about 1 or 2 per second, during the ground launch phase. Then it switches over to larger explosives about 0.5 to 1 kiloton for the in space phase. However I don't think it will ever be ground launched.
It has a lot of advantages, one of them being that you can get about 45% of your initial mass to LEO, as opposed to about 3% to 5% for chemical rockets. Also because atomic bombs are more efficient when they're larger, the ship gets a higher Isp for being larger. The original orioneers figured out a configuration that would have had a mission time to Mars of about 3 weeks!

NASA still funds the odd study on this concept, but with different configurations, and no ground launch. One such idea is MEDUSA, which uses a great parachute (I'm not sure what it would be made of.) to catch the explosions and pull the ship along rather than a giant, 1000 ton pusher plate with shock absorbers. Another is the mini-mag orion, a nice fusion of advanced concepts, using a plasma inflated magnetic sphere , ala Robert Winglee as a pusher plate. I'm not sure how either of these would work, as it's all a bit technical for me, but it's a fascinating subject. If you google any of these topics there's a lot more information out there than I could give, but a word of caution: Don't fall too in love with it. It's a great idea, but the obvious political showstoppers make it way too tragic. I don't think anyone will start developing this technology until after we establish a real presence in space.

Apologies to p1c3rd for hijacking this thread. :)


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Post    Posted on: Mon Apr 18, 2005 7:06 am
Hello, Marshall,

I will have to have another new look into Walter's book after the last short one yesterday in the evening - because of your mentioning of a requirement of internally confined fusion. Walter really is speaking of Orion using a pulsed fusion engine too - but he say it has been an additional alternative that has been studied.

As far as I understand it there never has been the intention or plan to launch by pulsed fusion engine from ground - it seems to be a launch from orbit and one approach is to get the fusion explosives form the jovian atmosphere which would mena a launch out of a jovian orbit.



Hello, Stefan,

I had a look into Walter's book yesterday late evening. He is speaking of micro-explosions and small pellets. As far as I remember currently Walter says that the total weight of Daedalus would be 450 tons and that of Orion would be 40 tons - but I will have another look. It's total weight - not the weight of the micro-"bombs".

I have to correct me concerning the time of travel - Barnard's Star would be reached after 50 years but Alpha Centauri would be reached after a decade. So given a launch in 1965 arrivals would be 2015 at Barnard's Star or 1975 at Alpha Centauri. These are estimations by Ulrich Walter - slight corrections might be required.





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Post    Posted on: Mon Apr 18, 2005 3:40 pm
Here in short what I found in Walter's book:

Walter is speaking of little micro-explosions of the force of one ton TNT. According to his book little pelletscontaining fusion explosives would be ignited by intense laserbeams. Specific impulse would be one millionseconds and v(ex) = 0,03c..

Having found that method pulsed micronuclearfusions have been propsed for Daedalus too. Daedalus would have had a weight of 450 tons..

The microfusionpellets would contain Deuterium or He3 – He3 would be taken from the jovian atmosphere.

Walter explicitly says that this technology today is no problem – with the exception of taking He3 out of the jovian atmosphere. It seems that we would be left to using Deuterium.

Concerning Daedalus Walter provides a graphic in which he is using bemas of relativistic electrons – he seems not to mention those electrons in the text.




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PS: It will be very interesting to look for ways that enable privates to develop and construct such p├╝ulsed fusion engines. Requirement for passenger travel throughout the whoel soalr system is decades or centuries away - sufficient time.


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