Bussard ramjets?

[drakesdoom]

I am the only one that thinks an engine design that could cruise at even 1% of the speed of light without using on board fuel would be awesome? That would never be useful for manned travel but what about probes, a comm buoy outside the solar wind bubble, or an automated barge?

Not to mention 2-4% would not be impossible.

[Ralathon]

I am the only one that thinks an engine design that could cruise at even 1% of the speed of light without using on board fuel would be awesome? That would never be useful for manned travel but what about probes, a comm buoy outside the solar wind bubble, or an automated barge?

Not to mention 2-4% would not be impossible.

At 1% the speed of light it'd take four and a half centuries to get to the nearest star. So it is completely useless for commerce between star systems. By the time your goods reach the star they're dated four centuries. It'd be easier to just send the information on how to build stuff, that'd only take 4.5 years to arrive.

A comm buoy outside the solar wind bubble is useless as well. What could it communicate with that you can't communicate with from earth? And it's not like you can use it for good reception everywhere in the solar system, round trip messages would take hours. It's faster to just send the data point to point.

And you couldn't even use it within the solar system because the particle density for the solar wind is way lower than that of interstellar space. It'd choke on a lack of reaction mass. Not to mention that by the time you get it up to operational velocity you already need to start slowing back down to avoid overshooting your target.

[christok]

A comm buoy outside the solar wind bubble is useless as well. What could it communicate with that you can't communicate with from earth?

That's not entirely correct. From a great distance, the sun could be used as a gravitational lens, giving truly enormous (directional) range.

[shynung]

You miss read what I said: a warpdrive would cut the travel time to the nearest star down to 2 WEEKS, which is a round trip of about a MONTH. That's a third of the time it would take a VASMIR propelled Mars mission to just get to Mars. Even if it was just a simple land and return, that's all we would need to ignite the public interest. "first man to walk on another planet around another star" "(insert astronauts name), faster than the fastest man alive!""Star Trek: it's no longer fiction" All of those headlines have quite a ring to them. If we can build an FTL ship, no matter how expensive, it would still be more economical/feasible/practical then a Bussard Ramjet. Hence why i support NASA's development and testing of a warpdrive.

Ironically, you just missed my point. What I meant was, why would someone go to a nearby star in the flesh, rather than using probes or rovers? No matter how fast the ship is, if you're doing an interstellar Apollo mission, funding it is going to be difficult, especially if the same mission could be done efficiently with a smaller, cheaper probe. Besides, testing the interstellar drive for a Terra/Jupiter/Saturn shuttle would probably have made more returns of investment. Even if we can send another ship to another star, the most we're going to launch is probably a probe.

Also, enlighten me further on how an FTL ship is going to be cheaper and more practical than a Bussard ramjet ship for any specific mission. How about a 100 ton ship to Gliese 581c (22 lightyears away)?

[cantab]

At best, we're conducting fundamental physics research that may lead to FTL travel. At worst, it's utterly impossible, just as Einstein predicted. While I'm not hubristic enough to say it won't happen, delaying development of technologies that work on the physics we know in the hope the physics we don't know will yield a breakthrough is folly. It's not trying to run before we can walk, it's trying to run before we've even discovered we have legs.

[NASAFanboy]

I'll just imagine that once the Acclubierre drive is developed for practical use, humanity will go interstellar. No matter if we're building our starship from Delta IV launches, no matter if we have to send the crew (If there is one) up in Soyuz or CCDev launches, and no matter if our starship is powered by a NTR and the whole thing had a main computing system called Linux, Mac, or Windows. Then we surprise the aliens with either one heck of a rickety primitive starship (Think a supersonic plane made of wood) or stumble upon some lesser species and start our conquest of the universe.

Sure, we have to walk before we run, and I agree with that on terms of slower than light travel to another star.

But getting the acclubierre drive, would be like suddenly recieving an automated exo-skeleton that could make you run faster and better than you could ever imagine.

Then in that case, why walk?

[shynung]

Sure, we have to walk before we run, and I agree with that on terms of slower than light travel to another star.

But getting the acclubierre drive, would be like suddenly recieving an automated exo-skeleton that could make you run faster and better than you could ever imagine.

Then in that case, why walk?

Because walking to a destination takes less energy than running to the same destination, therefore being more efficient?

Using your exoskeleton analogy, mechanical objects, especially one as complex as an automated exoskeleton, would probably need a powerful energy source, which is often not readily available, not to mention the constant need for maintenance. Biological legs, on the other hand, require only regular intakes of food, which people already do, in addition to keeping oneself healthy.

Alcubierre drives work in principle by bending, or warping, the space around it. How it is supposed to do this, however, aren't certain as of yet, but I predict it is likely to involve some complicated machinery that makes fusion reactors look like middle-age technology. Nuclear thermal rockets would be much simpler by comparison, even if we included the scoop to make it a Bussard ramjet.

By these arguments, I think that, even if Alcubierre drives were already invented, they would not be a commonplace technology for quite some time. How long, however, I am not certain.

Edited May 11, 2014 by shynung

[Jouni]

The Alcubierre drive is just a thought experiment. It may be compatible with the current understanding of physics under some assumptions, but there's no particular reason to believe that it would actually be possible, and even less reasons to believe that it could be used for actual faster-than-light travel.

Theoretical physics is full of all kinds of speculative ideas these days. It's better to be suspicious of then, unless the connection to experimental physics is well-established.

[Beowolf]

No matter if we're building our starship from Delta IV launches

I admire and even share your enthusiasm, but math and physics aren't being cooperative. If aliens landed and handed us a gift of an Alcubierre drive, we couldn't use it. Let's just ignore the requirement for "exotic matter" and only consider the antimatter fuel. The theoretical minimum fuel for your drive is 750 kg of antimatter per warp. Even if you just want a quick trip to the moon and back, that's 1500 kg of antimatter.

Quoting from Wikipedia: Recent data released by CERN states that, when fully operational, their facilities are capable of producing ten million antiprotons per minute. Assuming a 100% conversion of antiprotons to antihydrogen, it would take 100 billion years to produce 1 gram or 1 mole of antihydrogen (approximately 6.02×1023 atoms of antihydrogen).

So, to fuel this drive for a single round trip to anywhere would require 1,500 x 1,000 (grams to kg) x 100 billion years. According to NASA, the electricity for that would cost $62 trillion x 1,500 x 1,000.

And we've only been able store antimatter for about 20 minutes.

I'm sure a big global push could find ways to improve those numbers by 10, maybe even 100, in a single lifetime. But as you can see, that isn't even a single drop in the bucket.

We walk before we run not as a choice, but because it's the only way. In the movies, mad scientists work alone and build incredible wonders. But in the real world all technologies are tied together in a billion complex ways.

[NASAFanboy]

I'll guess that most of you missed the words "for practical use".

Practical use means you can power it. If you can't, then it's not up for practical use.

[shynung]

I'll guess that most of you missed the words "for practical use".

Practical use means you can power it. If you can't, then it's not up for practical use.

It still will take an awfully long time until this phrase become relevant. Forget antimatter, we haven't even have a working fusion reactor as of now.

[NASAFanboy]

It still will take an awfully long time until this phrase become relevant. Forget antimatter, we haven't even have a working fusion reactor as of now.

I'm afraid that I have to agree with you.

At the earliest, the drive won't be available for another century.

Shame we might not live to see it.