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Relativistic Spaceship

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Re: Relativistic Spaceship

#371

Post by xattt »

pants2 wrote: post #261
ryandrake wrote: post #27

Earlier quoted context omitted.

Sure, there are plenty of practical problems that would make the trip impossible. The fuel mass alone that would have to be shot out the back to make that trip would be something on the order of 800 million times the mass of the payload (you). So a 100kg person sitting in a 100kg spaceship would require something like 160 billion kg of fuel, assuming zero energy loss in burning the fuel. Relativistic rocket calculato…

Fun fact: if you got 250 MPG in a space car loaded up with as much gasoline as there is water in the ocean, you could could drive to the edge of the observable universe.

I knew there was a reason VW made the XL1.

Re: Relativistic Spaceship

#372

Post by denton-scratch »

eru wrote: post #301
BHSPitMonkey wrote: post #243

Earlier quoted context omitted.

And how many in that group are actually fit to spend many years living that lifestyle without losing their mind and getting into deadly fights with one another? And who's covering the great expense of building these generational colony ships and training their only inhabitants, only to have them zip away never to be heard from again? (With no benefit other than believing there's a slight chance we've succeeded in mak…

As humanity becomes more numerous and richer, the fraction of humanity you need that have such strange ideas and desire keeps shrinking. (Btw, I share your intuition that the number of people willing to sign up for a one-way trip to the stars, or even just Mars, is fairly low. However, if you already look at people who are dedicated enough to become astronauts, I suspect the additional filter of asking for one-way-tr…

> 10-20% of current astronauts would be willing to sign up.

Astronauts seem to me to have a higher propensity for kookiness than the general population. You may be right.

Re: Relativistic Spaceship

#373

Post by _factor »

pants2 wrote: post #261
ryandrake wrote: post #27

Earlier quoted context omitted.

Sure, there are plenty of practical problems that would make the trip impossible. The fuel mass alone that would have to be shot out the back to make that trip would be something on the order of 800 million times the mass of the payload (you). So a 100kg person sitting in a 100kg spaceship would require something like 160 billion kg of fuel, assuming zero energy loss in burning the fuel. Relativistic rocket calculato…

Fun fact: if you got 250 MPG in a space car loaded up with as much gasoline as there is water in the ocean, you could could drive to the edge of the observable universe.

Does this account for traffic?

Re: Relativistic Spaceship

#374

Post by TheOtherHobbes »

heads wrote: post #313
MilStdJunkie wrote: post #26

Earlier quoted context omitted.

Every proton would have the energy of a baseball. It's bananas. Granted, space is really empty, but it's not that empty, somewhere around a hundred atoms per cubic meter. Your ship might look like a very, very long shooting star. Probably dialing the speed down a touch would be worth it for whatever your shielding material is, but who knows? We're talking miracle engines here. I think in the "Valkyrie" ship-on-a-stri…

If you’re doing 2e8 m/s, your ship is long and thin with a 1m3 nose cone, and space has 100 baseballs per m3 then you’re being hit by 2e10 baseballs a second. How do I get an idea for what 20 billion baseballs (2TJ) feels like? Apparently bullets are about an order of magnitude more energetic than baseballs (800J vs 80J) so I guess I could try to build my intuition based on being shot ~2 billion times a second instea…

It's clearly not a solvable problem with current ideas about technology. No amount of ice, rock, magnetism, or Magic Unobtanium is going to make this practical.

I'm not even sure about warp drives. Bending spacetime one way means it has to squish back the other way. The energy released might not affect the ship - possibly - but I'd be surprised if it didn't affect the spacetime it had just passed through.

Some kind of new physics might make all of this possible, but - by definition - we have no idea what that might be.

Re: Relativistic Spaceship

#375

Post by aaron695 »

badosu wrote: post #256
eh_why_not wrote: post #107

Beautiful! For the comments saying we "just" need to maintain a 1G acceleration, should point out that as the ship approaches the speed of light, its mass increases [0]. And as the mass increases, so does the thrust required to maintain that acceleration. So that engine better be able to tap into some magical energy source, otherwise it can't maintain the acceleration at the higher speeds. :) [0] https://en.wikipedia…

The "increasing mass" stuff is more to make it easier for calculations and learning (with imo terrible consequence to physical intuition) than an actual physical concept. This video does a good job talking about the issue: https://www.youtube.com/watch?v=6HlCfwEduqA

[dead]

Re: Relativistic Spaceship

#376

Post by 867-5309 »

ryandrake wrote: post #12

Great visualization of the unintuitive nature of special relativity. It's kind of mind blowing to realize that if we could accelerate our spaceship at a mere 1G continuously, we could visit the center of the Milky Way in under 20 years (spaceship time), totally do-able in a human lifespan. Of course 27900 years would have passed on Earth, so you wouldn't be able to tell anyone about your vacation.

>27900 years would have passed on Earth, so you wouldn't be able to tell anyone about your vacation

you could tell them when they overtake you due to incessant obsolescence

Re: Relativistic Spaceship

#377

Post by ikekkdcjkfke »

a_gnostic wrote: post #351
MilStdJunkie wrote: post #26

Earlier quoted context omitted.

Every proton would have the energy of a baseball. It's bananas. Granted, space is really empty, but it's not that empty, somewhere around a hundred atoms per cubic meter. Your ship might look like a very, very long shooting star. Probably dialing the speed down a touch would be worth it for whatever your shielding material is, but who knows? We're talking miracle engines here. I think in the "Valkyrie" ship-on-a-stri…

A magnetic Ramjet could help (1) 1. https://www.sciencedirect.com/science/article/pii/S009457652...

Already patented?

Re: Relativistic Spaceship

#378

Post by wnkrshm »

xattt wrote: post #370
GuB-42 wrote: post #193

Earlier quoted context omitted.

Even if you managed to avoid matter, at some point, photons will start to become a problem. As you continue to accelerate, eventually, the cosmic microwave background itself will become deadly X-rays.

X-ray sources would turn to gamma rays. Not that it’s any better that X-rays. Other comments suggested lead plates. It would quickly get irradiated and would probably need to get shed as soon as you got to a destination.

No accounting for particles yet, which you'll also keep hitting, making your ship's materials radioactive and causing lots of secondary particle showers, bremsstrahlung and the likes.

Re: Relativistic Spaceship

#379

Post by jcul »

satvikpendem wrote: post #250
e40 wrote: post #227

Earlier quoted context omitted.

My second favorite sci-fi book of all time. Three body being the first.

Indeed. Have you read the rest of the series? It just gets crazier and crazier.

The rest of the hail mary series?? Or Three Body?

I have read two of the three body books, but I wasn't aware of a sequel to project hail mary, would be very excited if that's the case!

Re: Relativistic Spaceship

#380

Post by jcul »

ozim wrote: post #362
insane_dreamer wrote: post #303

Earlier quoted context omitted.

I like sci-fi, and enjoyed Hail Mary very much

It is not a bad book but I'd say for sure over-hyped. As much as I enjoyed reading it, I would not recommend it as "must have" if someone was into "The Martian". It is not a "must have" more like it is OK for general public and for hardcore sci-fi fans I would say that I can see how it could be disappointing. But yeah no one can easily appease hardcore fans anyway :)

I read it without any expectations and without knowing anything about the plot.

It was just recommended to me by someone, but I'm usually into sci-fi, stuff like Greg Egan.

I really enjoyed it, but maybe I would have been disappointed if I was expecting more of a mind melter!

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