[Pyrotex]

Moderation note:
The first 10 posts of this thread were originally in the thread Spaceship Design. They were moved to this new thread because they don’t have much to do with the thread’s original topic of the popularity of spaceship design ideas, circa 4/26/2006.

Let's wander over to the very edge of plausibility, shall we?

In the last decade, scientists have created Bose-Einstein condensates, often using Beryllium atoms. At extremely low temperatures, a cloud of these atoms cease to behave as a cloud of atoms, and behave instead as a wave phenomenon. S'fact.

Now... what if these waves could be "transmitted"? And received by another properly tuned BEC chamber? Even if this only worked with simple atoms (not molecules), what we have here is the possibility of transmitting fuel.

Design yourself a personal rocket ship. Say, about the size of an 80-foot sailboat. It has wings for flying, landing gear for landing, and hybrid jet/rocket engines that can operate on hydrogen as fuel while flying in our atmosphere, or on hydrogen/oxygen while performing as a pure rocket.

It contains two very under-sized fuel tanks. The craft would be totally worthless, except that it also contains a BEC Receiver! A station on the ground can "transmit" oxygen and hydrogen to the BEC Receiver, essentially keeping the craft's fuel tanks filled at all times.

It's only a teensy leap of imagination. But it results in a ship with virtually unlimited Delta-V. As long as you are "in range" of the BEC Transmitter.

[Thunderbird]

Originally Posted by Pyrotex

It contains two very under-sized fuel tanks. The craft would be totally worthless, except that it also contains a BEC Receiver! A station on the ground can "transmit" oxygen and hydrogen to the BEC Receiver, essentially keeping the craft's fuel tanks filled at all times.

It's only a teensy leap of imagination. But it results in a ship with virtually unlimited Delta-V. As long as you are "in range" of the BEC Transmitter.

Holy shit Batman !!! this is my personal fantasy craft. I had know idea this was remotly possible. This would make Moontanmans space station a reality.

[Moontanman]

Originally Posted by Thunderbird

Holy shit Batman !!! this is my personal fantasy craft. I had know idea this was remotly possible. This would make Moontanmans space station a reality.

T-Bird I already know how to do that, nuclear, It simply sounds too good to be true, if it is possible to transmit a BEC then you have to have elements that can form a BEC and can also be rocket fuel and oxidizer. Not sure if oxygen or hydrogen will form a BEC. Does anyone know?

[Jay-qu]

Theoretically anything should form a BEC at low enough temperatures, I just think Rb and others are used because they are the easiest for some reason or another.

Our uni is setting up a BEC generator this year and I will be doing a project on it

When I learn more I will let you guys know!

[CraigD]

Originally Posted by Pyrotex

In the last decade, scientists have created Bose-Einstein condensates, often using Beryllium atoms. At extremely low temperatures, a cloud of these atoms cease to behave as a cloud of atoms, and behave instead as a wave phenomenon. S'fact.

Correct about the dates for actually producing a BEC – according to the wikipedia article, the first one was produced in 1995 (straight-out winning the 2001 physics Nobel prize!).

However, I think Pyrotex misunderstands the “wave-like-ness” part. According to quantum mechanics, all particles behave as wave phenomena. The wave we’re talking about is (allowing a pit of poetic license) a “probability wave” – the square (complex conjugate, to be technically correct) of its amplitude at a point in space at a particular time gives the probability that the particle will be found there and then.

To the best of my knowledge, what’s special about a BEC boils down to (if you’ll pardon a refrigeration pun) boils down to two main things:

• It’s very, very cold (equating to having a very low average speed), and many times more massive than its component particles, so it’s associated de Broglie wavelength is very long.
• Even though it’s composed of fermions (particles with half-integer spin, such as electrons and the quarks in protons and neutrons), it can be considered a single, composite, boson (particles with integer spin, such as photons and gluons). This means it follows the Bose-Einstein statistics, rather than the Fermi-Dirac statistics. A significant consequence of this difference is that there’s a limit to how many fermions can exist in a given volume, but no such limit for bosons.

The Nobel laureates at the BEC Research Groups at JILA and NIST (who have lots of interesting reading material on BECs at their website) seem mostly interested in the second of these, especially what happens when a BEC stops being a BEC, and is suddenly a bunch of fermions closer the its statistics permit, which is something like a tiny supernova (see the new-ish thread “investigating a Bosenova”). What we’re interested in as a possible “remote spaceship fueling” system, however, is the first one.

For something slow and massive, like a BEC, its be Broglie wavelength is longer than something faster and less massive, like an electron of a proton. Most of the time, this wave nature is interesting to researchers because it can be made to produce “optical” effects, such as interference patters, with beams of particles like electrons and protons, but it means, fundamentally, is that we’re less sure of a guess about where the particle is – the particle, in this case, being the entire BEC.

Having set up the background on BECs a bit, I think we can tackle pyro’s main proposal:

Originally Posted by Pyrotex

Now... what if these waves could be "transmitted"? And received by another properly tuned BEC chamber? Even if this only worked with simple atoms (not molecules), what we have here is the possibility of transmitting fuel.

Here, as best I can tell, the idea trips on its basic physics and falls spectacularly on its face, because while we can, in principle, make the de Broglie wavelength of a BEC very large, this just means we don’t have a good guess as to where it is, not that a good guess is that it’s in a particular place of our choosing. In short, a BEC teleporter is intrinsically a “matter loser”, not a “matter finder” – you simply can’t have it both ways, generating a low probability of a chunk of matter being in the transmitter, and high one of it being in the receiver.

There are other possibilities for a matter teleporter-based remote spaceship fueling system, such as traversable (even if only by scrambled-up, atom size matter) wormholes, but at present even the best minds on the subject (eg: Michio Kaku) have only the tiniest clues on how to make one, or even if it’s possible (some major players, such as Steven Hawking, argue strongly that it’s not). Though my recollection is hazy, I remember a SF story, pre-1975 by Poul Anderson perhaps, that described such a spaceship. I don’t think the idea has made it past semi-firm sci-fi status yet.

A possibility that doesn’t require any exotic physics might be termed the “don’t be in such a damn hurry” scheme, where rather than tinkering with quantum wave functions or the fabric of space-time, you just shoot the fuel across space to your ship, say as pellets of ice. The engineering challenges of accelerating even the tiniest projectile to a decent fraction of c, aiming it precisely enough to hit a caching device, then catching it without something dreadful happening, are, to say the least, daunting, but in basic principle, it should be possible.

[TheBigDog]

Great post Craig. I am confused on one point though; was Pyro suggesting the teleportation of these particles, or the transmission of these particles? I envisioned the transmitter sending a beam that is aimed at the ship, which catches the particles via a receiver and places them in the fuel tanks. The beam would be a trickle of fuel, with the tanks allowing a buffer for when a greater flow rate is needed for short periods.

Bill

[CraigD]

Originally Posted by Moontanman

Not sure if oxygen or hydrogen will form a BEC. Does anyone know?

Originally Posted by Jay-qu

Theoretically anything should form a BEC at low enough temperatures, I just think Rb and others are used because they are the easiest for some reason or another.

I agree with Jay – it should be possible to make a BEC out of any atoms.

The main challenge in making a BEC is cooling. The magic temperature for the 1995 NIST-JILA experiment was about 0.00000017 K, pretty close to as low as you can go. This sort of cooling requires exotic techniques like laser cooling, which is roughly analogous to trying to get pool balls to stand still right after a hard break by shooting them with a rapid-fire b-b gun while wearing a blindfold and earplugs, with the allowed cheat of a little ramp to let some of the faster moving balls jump off the table. The more massive the “balls”, the easier this is to do, so an atom like Rubidium, mass about 85.5, is easier than Hydrogen or Oxygen at 1 and 16, respectively.

Really accomplishing laser cooling is very hard (they wouldn’t give out Nobels for it if it was easy, would they? ), requiring accounting for resonance of the atoms, their chamber, and the laser. Rubidium is, according to what I’ve read (with little detailed comprehension), in a “sweet spot” given equipment cost and availability, so was and remains a popular choice for BEC experiments.

[Janus]

Originally Posted by Pyrotex

Let's wander over to the very edge of plausibility, shall we?

In the last decade, scientists have created Bose-Einstein condensates, often using Beryllium atoms. At extremely low temperatures, a cloud of these atoms cease to behave as a cloud of atoms, and behave instead as a wave phenomenon. S'fact.

Now... what if these waves could be "transmitted"? And received by another properly tuned BEC chamber? Even if this only worked with simple atoms (not molecules), what we have here is the possibility of transmitting fuel.

Design yourself a personal rocket ship. Say, about the size of an 80-foot sailboat. It has wings for flying, landing gear for landing, and hybrid jet/rocket engines that can operate on hydrogen as fuel while flying in our atmosphere, or on hydrogen/oxygen while performing as a pure rocket.

It contains two very under-sized fuel tanks. The craft would be totally worthless, except that it also contains a BEC Receiver! A station on the ground can "transmit" oxygen and hydrogen to the BEC Receiver, essentially keeping the craft's fuel tanks filled at all times.

It's only a teensy leap of imagination. But it results in a ship with virtually unlimited Delta-V. As long as you are "in range" of the BEC Transmitter.

Besides the problem of transmitting BEC, already pointed out, I see another fly in the ointment here. Unless you are willing to ignore the law of conservation of momentum, the Fuel arriving at the tank will have the momentum it had when transmitted. Meaning it will have a relative velocity wrt to the craft equal to the craft's relative velocity to the Earth, and this velocity will be in opposition to the craft's velocity. Once the craft reaches a velocity equal to its exhaust velocity( about 4500 m/s for hydro-oxy) the momentum it loses to the incoming fuel will equal any momentum gained by burning the fuel, and it will gain no more velocity.

To get around this, you would have to pump extra energy into the "transmitted" fuel such that it's velocity matches that of the craft on arrival. This will take just as must energy as it would have if you had just carried the fuel with you on the ship in the first place. So in reality, your delta v would be limited to how much energy you can pump into the transmitted fuel.

[Jay-qu]

Originally Posted by CraigD

I agree with Jay – it should be possible to make a BEC out of any atoms.

The main challenge in making a BEC is cooling. The magic temperature for the 1995 NIST-JILA experiment was about 0.00000017 K, pretty close to as low as you can go.

Well.. its about as close to absolute zero as we are, temperature is a logarithmic scale and there is plenty more order's of magnitude to go down through..

Laser cooling is very cool, its a very clever application of doppler shift!

[modest]

Originally Posted by Janus

Besides the problem of transmitting BEC, already pointed out, I see another fly in the ointment here. Unless you are willing to ignore the law of conservation of momentum, the Fuel arriving at the tank will have the momentum it had when transmitted. Meaning it will have a relative velocity wrt to the craft equal to the craft's relative velocity to the Earth, and this velocity will be in opposition to the craft's velocity. Once the craft reaches a velocity equal to its exhaust velocity( about 4500 m/s for hydro-oxy) the momentum it loses to the incoming fuel will equal any momentum gained by burning the fuel, and it will gain no more velocity.

Would that not imply that the earth emitter would be accelerated toward the ship?

Ordinarily anything transmitted to a moving target would have to have greater velocity than the target - thus the target would gain momentum by catching it. I guess we're assuming the large wavelength of the BEC would make some kind of teleportation possible where the wave is not in the direction of the particle's momentum. A question open to the floor: Is that what we're supposing? Like a photon with a really large wavelength - It could be captured at a location orthogonal to it's direction of travel and thus transfer it's momentum 90º (or so) from the emission / capture line?

I ask because that sounds really interesting and something I've never heard before. Using a large wavelength to transport something sounds potentially plausible and really intriguing.

-modest