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public space travel in 20 years?

Posted by: 4thdimension - Mon Jul 16, 2007 10:09 pm
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public space travel in 20 years? 
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Post    Posted on: Wed Aug 01, 2007 3:46 pm
Metallic hydrogen on its own as a monopropellant would definitely be out of the box thinking, but it would also be a very good example of the "not cheaper or easier than existing technology" that I was talking about.


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Post    Posted on: Wed Aug 01, 2007 4:09 pm
As many have already said. Its depends on the details. If we can produce it and store it safely it would make rocket *HEAPS* better. Its not just a monopropellent, its a super monopropellent giving huge mass ratio reductions. Its would have better than 700sec of ISP (IIRC) and would allow a SSTO rocket with large safety margins to be easily build, even with steal and simple safe low pressure engines.

Its similar to having carbon nanotubes with 1/2 the strength needed for a SE (30GPa). You could now easily make the airframe so light yet so strong that everything gets real safe and because its reusable, real cheap.


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Post    Posted on: Wed Aug 01, 2007 11:43 pm
Hi,
I just stumbled across this.. nice to see you people have already hit some similar ideas.

Yes I agree about the carbon nanotubes too, and lots really is happening there.

I wasnt using this as an example of something that is likely. What I meant was that while people are waiting for an antigravity breakthrough, a breakthrough in this area (or a hundred other seldom discussed long shots) might come along... I have heard many people discuss antigravity but this is the first time I have stumbled over the idea of metastable metallic hydrogen, even though unlike antigravity, it may fit within the framework of current physics.

As for comparing it to LOX/LH2 rockets, you would have to carry that argument to the writers of the wiki article. They are claiming 5 times better, presumably from the energy released when the material expands back into hydrogen.

And yeah. I admitted that even if a breakthrough made this a hot topic, it would take a long time to base a rocket on it, so it probably wouldnt apply to the 20 year goal. Although, a breakthough now that implied travel would be cheap in 30 years would probably immediately boost the space industry. For example people might seriously start designing space solar power or huge orbital hotels, on the assumption that the tech to launch it would arrive on time.


Last edited by BEM on Thu Aug 02, 2007 11:31 pm, edited 1 time in total.



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Post    Posted on: Thu Aug 02, 2007 1:40 am
Martin Tajmar has a short paragraph about metallic hydrogen in his book "advanced space propulsion systems":

The estimated specific impulse is 1700 seconds, the density about 1.15 g/cm^3, the necessary pressure about 1.4 Mbar.

He also lists at the end of his book several potential breakthrough propulsion systems, e.g. using zero point energy.

He shows a nice example about the problem with breaktroughs, you can't predict them:
At the beginning of the 20th century, he wrotes, scientists "proved" that it is impossible to fly with machines heavier than air, in the 1930s scientists "proved" that is impossible to fly to the moon because of the enormous energy needed.

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Post    Posted on: Thu Aug 02, 2007 2:18 pm
It just occurred to me that we have neglected the single answer which could produce exactly the dreamed-of results requested by the thread's originator.

Of course, we are conditioned by years of fearmongering to do just that; i.e. pretend it doesn't exist.

I'm talking about NTR. Twice the performance of current impulse propulsion methods. Mature and well-proven technology. Significant capacity. No significant material or implementation breakthrough required.

What if India started building an NTR fleet and offering orbital lift for US$50 per pound? What would happen to the market? What could other governments do to stop them from using the technology that they have already developed? If they used He as the propellant they wouldn't release any atmospheric radiation, it wouldn't be materially different from any number of nuclear powered vessels operated by other countries.

Could LEO become significantly populated in 20 years? A dozen hotels or so? A vacation on orbit for the price of a round-the-world cruise or something on that order? Lunar Safaris for US$200K?

Combine the physical reduction in cost due to nuclear power with the overhead reductions of labor in a non-European/non-US emergent economy... the potential does exist. The most significant barriers are political (although they are significant, I expect).

I don't consider it likely... just not impossible.


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Post    Posted on: Thu Aug 02, 2007 3:18 pm
NTR is not a mature technology by any stretch of the imagination. There are no operational NTR in existence. The few that were built did have some radioactive exhaust issues, although it was belevied to be a solvable problem.

Personally I don't think NTR from earth to LEO is viable with the current failure rates. But in space ie for a mars mission, especially a maned mars mission, it makes a lot of sense. But it would need a lot of R&D. doable in 20 years too.

I just can't see the current political climate warming to the idea however.


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Post    Posted on: Thu Aug 02, 2007 3:41 pm
delt0r wrote:
I just can't see the current political climate warming to the idea however.


...which is a much more difficult hurdle than any of the technical issues.

My point is, NTR is a much more technically plausible path to cheap and reliable access to space than anything else thus far posited in the context of this thread. Mono-hydrogen, anti-grav, space elevator... I don't expect to see operational implementations of any of these technologies in my lifetime (OK, to be fair I ain't exactly a spring chicken!) However, Boeing or Northrop of LockMart could field a flying SSTO NTR by the beginning of the next decade if there was sufficient motivation and minimal oversight. They couldn't do it cheap, mind you, but an entity not saddled with US labor costs might be able to make it fiscally reasonable in a real-world timeframe... if the politics were a non-issue.

Still, changing politics is generally easier than subverting the laws of physics.


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Post    Posted on: Thu Aug 02, 2007 4:37 pm
What about plain properly built rockets? ie a RLV SSTO. Its my pick, and far more likely than a NTR. I'm not going to go on about why/how, the usenet archives have that topic so throughly trashed to death already.

The biggest hurdle is a need. Lots of folk with not that much money "want" to go into space rather than "need" to go to space.... thats not really the kind of demand that air travel had for example, where there really was a need to get across the Atlantic quicker than many days of traveling or the pacific (I'm from NZ). Also space will probably always bit a bit harder than air travel. Just like air travel is a bit harder than sea/land travel.

all IMO of course.


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Post    Posted on: Thu Aug 02, 2007 5:22 pm
I concur with the bulk of your analysis... but I'm not sure that there is any plausible scenario in which the "need" (read: profitability) for spaceflight is sufficient to drive the spectacular investment required to achieve the wet-dream 20 year timeline using extant chemical rocket technology. However, I do think that it (conventional chemical propulsion) represents the path to routine space travel for the foreseeable future.

I think that tourism is going to be the driving economic factor in the launch vehicle renaissance, and I don't think that the fiscal numbers point to a scenario in which I can call my travel agent and arrange for a retirement dinner on the lunar surface. And I'm OK with that. At least we know that things are finally moving ahead in a proper market-driven manner and that there is a real-world chance that my children will be able to book extraterrestrial travel someday.

My whole purpose in suggesting NTR was to point out that in the realm of spaceflight, solving one problem (in this case performance) doesn't add up to space hotels the next day. By offering a nearly off-the-shelf solution which doesn't require unobtanium or ZPE or any other kind of voodoo, I can show that "we're still not there!"

Which is another way of saying "it's really more of a people problem"

You want routine spaceflight in 20 years? Quit complaining and fork over your $200K (or whatever RpK says they'll do, $100K or something) Short of getting a postgraduate education in advanced engineering, that is the best thing any individual can do at this point. And most folks are more capable of the former.


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Post    Posted on: Thu Aug 02, 2007 9:04 pm
NTR is definitely not cheap or easy; unless you still believe that electricity generated by nuclear reactors will be too cheap to meter.

It really shocks me how so many people just assume that new breakthrough technology will be cheap and easy. Maybe it is because of the giant strides in electronics that make computers cheaper and more powerful every year which we take for granted these days. But I do not know any other realm of human endeavor that has seen the stunning level of success as electronics. Certainly no transportation technology has done so. If transportation showed advances like electronics, we would be driving $100 cars that got 500 miles per gallon today. If you could make a $50 per pound to orbit rocket, then you could make a car like that too.


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Post    Posted on: Thu Aug 02, 2007 11:27 pm
There seems to have been a general consensus that current rockets could make public spacetravel affordable with sufficient motivation, if never cheap.

This discussion of other technologies may be just because we have moved on to brainstorming possible breakthroughs. I only mentioned metastable metalic hydrogen because it was an example of an unknown.

I would like to see some more suggestions of motivations that could appear.


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Post    Posted on: Thu Aug 02, 2007 11:32 pm
It's ironic that perhaps all that is needed is better engineering and management, not technological breakthroughs.


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Post    Posted on: Thu Aug 02, 2007 11:55 pm
If a real motivation comes along, interest in space could take off faster than expected.

Suppose for example we develop a self replicating factory using solar power and moondust, but it is fairly slow. For example it takes ten years to copy itself. You can deliver it once to the moon, and in a hundred years it would have increased a thousand fold.

You might think we would send just one and wait. However people would not be thinking in terms of cost effectiveness. Suddenly we are faced with the fact that the moon is going to belong to someone. If america sends one factory and russia sends two then russia will end up with twice as much of the moon. Despite any UN resolutions I expect there would be a massive land grab, with many launches and everyone claiming as much as they can.

This could happen right now even before we had perfected the factory. If we felt confident we would have it in ten years from now, countries would probably start ramping up for those launches.


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Post    Posted on: Fri Aug 03, 2007 1:37 pm
quantumg wrote:
It's ironic that perhaps all that is needed is better engineering and management, not technological breakthroughs.


So says Elon Musk. And Burt Rutan. And Jeff Bezos. And John Carmack.

In 10 or 15 years we'll know whether they're right. I can't wait to see how this plays out. If I had a time machine my first destination would be circa 2012, just 'cuz the suspense is KILLING me!


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Post    Posted on: Fri Jan 04, 2008 1:59 pm
Just this moment your post, SawSS1June21, reminded me to the (most?) recent progress of software development methods or principles - Extreme Programming or XP.

Might an according method or principle developed in engineering rockts and vehicles also?

XP doesn't involve no breakthroughs or the like but simply application of known methods etc. to an extreme degree including some assisting an channeling principles that partially look a bit like incentives.

So what about chances that a kind of XE - Extreme Engineering - might enable public space travel - lunar, interplanetary - in 20 years?

John Carmack for example said a time ago that software to control a rocket or vehicle shouldn't include no subroutines but be one-dimensional code. He explained the reasons and expereinces in the General Armadillo Aerospace Forum if I remember correct - I think it was the Armadillo Aerospace Q&A thread.

Whast about it?



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