A Star Trek Reality - 20 Years to Build Enterprise

[Master_Ghost_Knight]

My take on nuclear purpolsion.... you mad?
Contrary to popular belief, explosives do not make good engins, specially in space.

why is it mad?
of all the concepts for travel within full percentages of speed of light, it seemed the most realistic with current technology to me.

Getting to a full percentage of the speed of light is easy given enough time, 0.01*C about 3,5 days at 1G ,1,8D in 2G or 24D in 0.1G (depending on the stress you are willing to pull), the problem is doing it efficiently, and I certainly wouldn't count a nuclear explosion as efficient. Lets say for the sake of argument that you would try to do it with a nuclear explosion, assuming that you can produce a shield thick enough to protect the craft from the radiation and have managed to fix all the technical difficulties, you would find out very fast that the results would be less than impressive.
Even though the detonation of the nuclear device could destroy most of the blast chambers ever build, the majority of the impact comes not from the device itself but rather from the rapid expansion of the air around it. Given that there is no air in space, besides the deadly and devastating shrapnel and radiation, it would just be a quite expensive light show, and all you have achieved is to waste a nuclear device worth of energy. You cannot beat the laws of Newton, for every action you must have an equal and opposite reaction, and until you have something to throw in the opposite direction I am afraid that your craft simply won't budge. People are very quick to try and blow shit up but they are not very good at figuring out what happens to the shit that is blown up.

Ok so now let's assume that you also take a gas with you to serve as propellant, how much acceleration are we talking about? And how would we be deploying the explosion? If we expect to take humans on board then the acceleration cannot exceed a couple of G or else you are just squashing people, when we launch people into space they are not launched full blown from a canon where they receive the full extent of the scape velocity right from the ground. Not only because the resulting atmospheric drag would burn everything out, but also because it would turn every occupants along with the craft itself into jelly filled pancakes. Even if there aren't any human occupants, devices have a quite finite acceleration that they can sustain before breaking down. So we are not talking here about a big blast that would deliver the goods from the start, but at best a succession of sequenced sustained blasts.

There is critical volume at which we expect to have a sustained nuclear reaction, even though there is a level of control this isn't like pumping gas, you can't simply shut it off and it can all go south really fast. Besides propulsion by an explosion is not the most efficient use of energy, most of the material will just fly ineffectively in different directions that it is intended, and most of the energy would just be lost into heat and radiation.

So here is the thing, you already have to take gas as a propellant, you already have to take nuclear material and a reactor and you are already limited in the amount of acceleration you can take. Then why not invest in a nuclear powered ionic accelerator? It uses the energy more efficiently, you won't need excessive amount of shielding, the accelerations are well within acceptable ranges (it may take a couple more days, but that isn't much more than what you already need) and save money in the process?

 

[Visaki]

I thought I remembered that Project Orion had something to do with this, and it does!

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

They really did make an honest go at the plans I think, including the problems Master_Ghost_Knight noted.

 

[nudger1964]

thanks for that - bit confusing to call their current development crew vehicle Orion too huh.

i think closest thing to what MGK is talking about is VASIMR - which as with anything else has its critics.
if they had a reactor for it id be a bit more optimistic - but one thing im pretty sure is that we wont be getting a 1.5Gw reactor in a space craft within 20 yrs

 

[Dean]

nudger1964

["¦] from how i read it, the 1G gravity comes from the rotating wheel. the constant acceleration is just how ion drive works...i dont think the 1G and the constant acceleration where linked in any way. ["¦]

Yes, I know. He was talking about a proposed form of artificial-gravitation (it's by no means the first time someone has suggested something like this). My point was that the applicable technology will decide the form of the craft, as opposed to the inverse of this, as BTE Danâ„¢ seems to think. Constructing a high-powered spacecraft , in any event , to look (literally) like an article of science-fiction, is not an efficient means of creating a "space-ship". If you want a genuinely feasible (realistic) science-fiction model from which to design a spaceship, look to novels of Arthur C. Clark, e.g. the Rama saga, most notably of all. A cylindrical spacecraft is far more efficient and far more productive use of space. Indeed, it's difficult to even discern how placing the power supply , as posited in that article , so far of the main axis of the ship; would even be able to work at all. So the Star Trek Enterprise is not going to work as a design concept, clearly.

All that aside, my primary point was that if we were able to achieve 1G of acceleration, we would thus have no need for the expense of artificial-gravity via. rotation. Even 0.5 of 1G (at constant speed) could reach Pluto in about 12.6 days. And could hence get us just about anywhere in this solar system in reasonable time. Beyond that, things become almost completely infeasible. Hell, it's physically possible to reach the edge of the Andromeda Galaxy at the same speed (which is 2.5×10[sup]19[/sup] kilometres from us at the moment, or 14.6 quintillion miles), in a "mere" (note the quotation marks) 54.7 years, by which time almost 3 million years would have passed on Earth, due to relativistic effects. But this is beyond impractical. It would also be a one-way trip for the crew even if it were possible, and also, we can't expect to find any fuel source that can sustain that speed for any great length of time (i.e. decades) with a finite amount of energy, especially considering all the debris that exists in space . . .

Master_Ghost_Knight

["¦] Contrary to popular belief, explosives do not make good engin[e]s, [e]specially in space.["¦]

["¦] today's 15yo don't know what the hell Star Trek is, we are getting old buddy.

*Chuckles*.
E. W. Roddenberry and company were in all probability high on crack when they conjured up the design for the Enterprise, as you can see in this replicated design (somewhat) in the posted link . . . Jesus F'en Christ, stanchions and massive pillars with four bulk pieces? One has to wonder why they never thought of giving the bloody thing wings while they were on it. Even for a science-fiction concept , let alone a workable design for a craft , I'm afraid you probably couldn't even try to create a design more prone to (eventual) catastrophic physical problems. And as for the mechanical dampening (a la energy) . . . wait . . . it IS still energy, and therefore, the dampening will dissipate as heat. . . and as we've already seen at some length, there are a literal plethora of other problems besides this. And this isn't a trivial problem . . .

And as I've already said, the most technically plausible designs for spacecraft likely come from authors like Arthur C. Clarke. Either that, or Silent Running (1972). An otherwise unintentionally hilarious film, no less. A bolted triangular-girder-latice design is not a bad idea for a full scale working spacecraft, possibly. This concept is prevalent through out science fiction (Space Opera) films. . .one of the most obvious problems with the "explosive" design is because there are simply too many ways for it to go wrong, such as if one of the conventional "bombs" fail to detonate, etc, etc.

 

[nudger1964]

a constant 0.5g acceleration is quite a technological jump though. I would think that would require unrealistic energy levels.
Centrifugal artificial gravity is way more likely.
If artificial gravity is a requirement, then thats pretty easy to achieve.
So far the research i have read about seems to conclude that the health effects can be avoided by quite a short periods in a small centrifugal chamber within a craft, and thats the assumption NASA seems to be working on for the moment - although there is nowhere near enough data yet to decide.

There are very easy ways to get artifcial gravity. The technology to use tethers is pretty much there now, so id imagine thats the way in which it will be done.
It dosnt need big vehicles, its cheap and dosnt add much mass...so its a bit of a no brainer.
But what is interesting is after all these decades in space, we still have very little idea of the effects of low gravity on the human body. we just know 6 months in zero is bad, but not much more than that.
The fact that no one is really working to understand the issue makes me think it will be a very long time before humans are traveling Mars like distances

 

[nudger1964]

I thought I remembered that Project Orion had something to do with this, and it does!

http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

They really did make an honest go at the plans I think, including the problems Master_Ghost_Knight noted.

just stumbled on a BBC horizon documentary on youtube called "To Mars by A-Bomb", made back in 1993.
it was a facinating project i must say