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Reaching 95% the Speed of Light


SadBot

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Perhaps they could ditch the sails into the black hole? They wouldn't need them anymore, right?

 

From what I understand, they would need those sails to navigate other places. The sails still can use solar wind, and from what sadbot says, it is the ship's only major form of propulsion.

The way most sci-fi stories explain sails are as a extremely thin layer of conductive material to harness solar winds. The sails usually can't stand up to any rigors and if debris flies through it thats the end of the sails. Most stories also have mechanisms for retracting the sails or deploying new ones.

 

On the topic of ships with solar sails, I remember reading a book about a race around the solar system, in which sails were the only thing allowed, and each ship was a tiny cabin big enough for a small crew each ship and sail used a different design in hopes of outrunning their opponents. If I can remember the title I will post it.

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Ahhh, thanks for that CraigD, it is all coming back to me now. And it just felt 'true' of how us human beings would discover the "uh oh!" of new technologies.

 

Remember some scene far into the distant future where they picked up some kind of radio transmission from something that was 'post-human'? That really freaked out the child version of myself 30 odd years ago! That was a great sci-fi moment of "Woah! My brain is full!" After all, isn't a sense of wonder and newness and adventure what we are after from sci-fi? Isn't a great sci-fi basically akin to doing drugs, but without the side effects?

 

In the perfect vacuum outside the collapsed universe, they’re able to shut down and repair their systems, then time their deceleration to make planetfall on an Earth-like planet about 13 billion years after the new Big Bang, where they all retire from astronauting, have kids, etc.

 

Yes, that's why it was such a memorable story! However, 'outside the collapsed universe' is a problematic thought. Isn't there no 'there' there? How can anything exist outside the universe? Isn't nothing nothing? According to a "Brief history of time" (which I read but barely understood due to my arts-background handicap), even perfect vacuum is something, because it has space-time. It has XYZ and time. How can a ship exist outside of that?

 

modest

They face their own mortality, etc, until the under-appreciated janitor on the ship says "ya know—ships used to throw ballast overboard if they needed more speed". The over-appreciated engineer says "by golly, that just might work! We could use the Penrose process, etc...". They abandon half the ship (which, of course, has an unfortunate passenger trapped on it) while the other half gets accelerated away from the hole at .95c.

There needs to be a really good punch up in here as well, just to increase the insanity! The janitor yells, "I don't want to die because you're too stubborn to try this idea! The ballast shoves into the black hole like THIS!" (Rams a kitchen fork through the engineer's hand) "and the ship goes shooting off like THAT..." (As the engineer wails and withdraws his hand). The Captain orders the 'janitor' (serviceman, pilot, whatever) to be restrained, while the Engineer stares down at his hand and mutters... "Like THAT! The Penrose effect!"

 

If you're good at writing funny, there could even be a good "Sorry about the fork!" line somewhere at dinner later on. Maybe the engineer enters the mess after the incident, where a survival party is being held, and everyone salutes him with a fork, at which point the 'janitor' (pilot, assistant astronaut, whatever) looks guilty, and says "Sorry about the fork".

 

Anyway, the point? Sci-fi is about whacky, wonderful new ideas. It is also most crucially about how people cope in those situations. If there is going to be a 'scene', it needs to be explained why these professionals are so pushed beyond their normal thought processes that they don't behave calmly and heroically like the Apollo13 crew did under Tom Hanks, but actually lost it in the middle of this crisis.

 

Maybe reading some of the 'crisis revisited' stuff on airline disasters? Black boxes reveal how airline crews interact in crisis, and doctors have even studied these scenarios to try and improve the decision making process in times of intense pressure. It would make fascinating psychological reading and maybe even prepare you for some good character studies and help flesh out the people in this grand epic narrative of travel across the stars.

 

theory5

From what I understand, they would need those sails to navigate other places.

No no! This is when they look around and try to build a "rudimentary lathe!" :phones:

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Modest~

 

I was reading about it and it does seem like a lot of the ship would need to be lost in order for this to work. That I will have to figure out.

To be honest, it's well over my head.

 

There is, apparently, no limit to the theoretical efficiency of the Penrose process if the object is electrically charged. If the object is not charged then the upper limit is 20.7%. I get that from: Energetics of the Kerr-Newman Black Hole by the Penrose Process. I assume this means that the exiting object has approx. 20% more energy than the object entering the hole. Using the relativistic kinetic energy equation,

[math]E_k = \frac{m c^2}{\sqrt{1 - (v/c)^2}} - m c^2 [/math]

Cutting the mass in half and increasing Ek by 20% to the smaller mass would only increase the velocity from .5c to about .68c. Like Janus was saying, the faster you go the more energy it takes to accelerate. So it sounds like you'd need them to charge the ship somehow... or, perhaps it is already from the sails. In that case, you could presumably loose little mass and be accelerated a great deal. The paper I linked says there is no limit... essentially, the greater the electric charge, the greater the acceleration.

 

Also, I'm not sure on how the Penrose process would work on a large object. There's this idea of negative energy in black hole thermodynamics that somehow has to comply with conservation laws making the whole thing work. Normally, I think it is explained that a particle becomes two entangled pairs one of which is swallowed by the hole while the other is not. I don't know if the Penrose process requires that same kind of explanation or how it could or would work on a large object. I know from perusing the article linked above that negative energy is involved, and half of a ship can't really be entangled with the other half :shrug:

 

Unless someone more knowledgeable could say, I'd have to find something to read on the process. I'm just not that familiar with this.

 

The ship, (how I have it written so far) is about a kilometer long, so plenty of ship to lose. There's another problem. The ships power is from the sails, which "deflect" charged particles (which come from the high powered particle accelerator). There's two sails and so the particles "bounce" back and forth at a fast rate. The first sale is large and is being pushed, the inner is smaller and focused on heating the sails and deflecting the charged particles to the larger sail. (In a nut shell)... So I'm not sure how thy could escape... Unless I incorporated both ideas. Just the initial thrust takes them to say... .7c and the black hole takes them to .95c. Hmmmm

 

No, they wouldn't have to use any significant thrust for the Penrose process. What I said about not having enough thrust to escape the hole was misleading. If the ship were broken in half, let's say, then the two pieces could drift apart very slowly. It would just be necessary that one piece crosses the event horizon. The other would stay in the ergosphere, never entering the horizon. But, at that point I'd assume the two peices could be quite close to one another and have no more than slightly differing trajectories.

 

I'll try to find something to read on the Process and see if I can get some solid answers. Also, sorry for the delayed response.

 

~modest

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However, 'outside the collapsed universe' is a problematic thought. Isn't there no 'there' there? How can anything exist outside the universe? Isn't nothing nothing?

Indeed :)

How can a ship exist outside of that?

Like you say,

This is when they look around and try to build a "rudimentary lathe!" ;)

:) I was rolling out of my seat laughing at that part of Galaxy Quest.

Anyway, the point? Sci-fi is about whacky, wonderful new ideas. It is also most crucially about how people cope in those situations. If there is going to be a 'scene', it needs to be explained why these professionals are so pushed beyond their normal thought processes that they don't behave calmly and heroically like the Apollo13 crew did under Tom Hanks, but actually lost it in the middle of this crisis.

Amen. There was a recent TV series, Defying Gravity, which drove me nuts for that very reason. The acting was good, but the way they wrote the characters... they often responded to situations with the emotional maturity of Jr. High kids. It drove me absolutely bonkers.

 

~modest

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The idea is brilliant! The other thing I think of as the do the maneuver to escape the black hole is that it is a move of desperation and survival, and as they exit at .95C they may have no idea what their final trajectory will be, or how they may slow down. So they survive but are subjected to a random fate of physics.

 

Bill

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Also, I'm not sure on how the Penrose process would work on a large object. There's this idea of negative energy in black hole thermodynamics that somehow has to comply with conservation laws making the whole thing work. Normally, I think it is explained that a particle becomes two entangled pairs one of which is swallowed by the hole while the other is not. I don't know if the Penrose process requires that same kind of explanation or how it could or would work on a large object. I know from perusing the article linked above that negative energy is involved, and half of a ship can't really be entangled with the other half :)

 

I seem to have found an answer to this. The negative energy associated with the Kerr metric arises for different reasons than negative energy in Hawking radiation. Entanglement is then not necessary. So, nothing to worry about. This process should work for a large complex object like a ship,

 

In the process a particle falls into the ergosphere where it splits into two or more particles. One of the particles might have negative energy, as reasoned from infinity. In such a case the other one will have more energy than the original particle. The particle with the negative energy will be swallowed by the black hole while the other one will escape to infinity with a net gain in energy. In order to gain energy it is not necessary to have a disintegration. A collision or any other process that will deflect the motion of a particle will do as well. Furthermore, the number of outgoing particles can be greater than two.

 

~modest

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