Reaching 95% the Speed of Light

[SadBot]

Hello!

 

I am new here!! Glad I found this forum, I've been reading it for the last few hours.

 

Anyway, I am young, going to school and just switched my major to Astrophysics/physics. Unfortunately I am still not very knowledgeable about many things in regards to this. I love learning about space time, and speed and travel. I got interested in this because I am a writer. (Or love to write, I should say). Currently I am working on a story and am stumped.

 

I feel I understand what would happen if a ship could reach 95% of the speed of light, but how to get there is another thing. I've gotten the ship to about 50% using solar winds and a high beam particle accelerator being shot at sails (Which I found to be a very viable theory), but the rest I can't figure out. I don't even know if there is a way.

 

Anyway, if anyone could help me out that would be great. Thanks!

[Theory5]

Greetings, Im Theory, I'm a freshman network engineer studying at Johnson &Whales University. Where do you go to school?

 

I'm horrible at math so I don't think I can help you mathmatically, but I have some questions, being a science fiction buff I love theoretical stuff.

I have read many books that indicate their ships move at near light speed without actually stating how, its usually a vague theory if that.

Would the particle beam accelerator be attached to the ship? if it isn't wouldn't the ship move too far away to focus the beam before it got really going? And about solar winds, wouldn't the ship move out of the solar system after a bit?

There are literally hundreds of theories and not so viable theory's in fiction that deal with moving close to the speed of light. Suppose your ship's engines can use zero-point energy taken from someplace (which would make some pretty unstable engines if over-heated or overloaded). Hyperdrive engines, which sends the ship into some sort of parallel universe where you travel much much faster... (hundreds of names that you can use or make up your own). Ram scoops are another way, except they need time to accelerate, but they can take fuel right out of space. Deceleration is a big issue though, all that energy needs to go somewhere.

 

anyways, once you finish your story you should post it. I would like to read it.

[SadBot]

Hey,

 

Thanks for the reply!!

 

The beam-powered high frequency particle accelerator, (that's the technical name) is actually aimed at the sails of the ship from (in my story) Mars.

 

Reading about these it seemed as though they have to be fired from a planet or asteroid or something. It wouldn't be able to be on the ship, but because of how it reacts to the sails the momentum is steady and fast.

 

The sails, using a static magnetic field to deflect charged particles which radiated from the beam, accelerated the space-craft from the momentum it caused. There are basically two sails that the particles "bounce" back and forth, crating the energy and momentum.

 

The only problem, (which I forgot to mention earlier) is that the part about going 95% is that is would be on accident. Something basically has to cause the ship to go that fast. I don't know if it is possible, but if it is that would be great.

 

More info on the story: The ship will be around Sirius. Going a little more than half the speed of light, (151,366.229 kilometers per second), they reach Sirius in a little over 14 years. (It is 8.6 ly away).

[Janus]

An accidental boost from 0.5c to 0.95c would be damn near impossible. It takes 14 times as much energy to reach 0.95c than it does to reach 0.50c. This means your accident would have to release at least 13 times the energy you already expended, and that is if all the energy went into accelerating your ship.

[SadBot]

See, and that is the problem. The 0.5c was easy enough to find a way, but that's the most I can get. (Which was on purpose). I'm thinking that I'm going to have to change that, but if someone has and idea on something that could cause that it would be greatly appreciated. :eek2:

[Theory5]

accidental? Well why didn't you say so! :-P

If you are writing science fiction you shouldn't change your story just because its impossible! There is some sort of science or sciency sounding thing that you can use.

If you can't think of something to propel them to Sirius, you could use something else, like a cold-sleep malfunction and they awake 14 years later :-P

 

Here is some things you might be able to use. The accidental part could be something sort of stock, such as time-space warp or flux that causes a massive energy burst.

Or encounter an alien device, or the beam from your particle laser is focused on the ship and the ship moves through a thin cloud of particles that has electrical disturbances periodically. The beam somehow ignites the cloud, or supercharges it or something and either creates a disturbance which catches the sails and catapults the ship like a strong wind catching a sailboat, or generates enough power in an explosive manner flinging the ship. both of these would send the ship on its course, give or take a few light-years or so because of the nature of the cloud, and you wouldn't be able to steer the ship while its flying through space.

[SadBot]

You know . . . I really like the cloud idea. Because of the nature of the particle beams focus if there was some cloud where, if the ship was in it during the time the beam hit the sails the extra particles "ignited" (for lack of a better word) could send the ship very quickly off course as well as knock out or fry some circuits. Navigation down. And with the nature of the duel sails the energy would stay constant.

 

Wow! Thanks man! That was great.

[Theory5]

You know . . . I really like the cloud idea. Because of the nature of the particle beams focus if there was some cloud where, if the ship was in it during the time the beam hit the sails the extra particles "ignited" (for lack of a better word) could send the ship very quickly off course as well as knock out or fry some circuits. Navigation down. And with the nature of the duel sails the energy would stay constant.

 

Wow! Thanks man! That was great.

Anytime. I think you worded it much better than I did. :-)

[CraigD]

Welcome to hypography, SadBot. :)

Anyway, I am young, going to school and just switched my major to Astrophysics/physics. Unfortunately I am still not very knowledgeable about many things in regards to this. I love learning about space time, and speed and travel. I got interested in this because I am a writer. (Or love to write, I should say).

Physics students who love to write ... well, IMHO that’s pretty much a profile of the perfect hypographer :phones:

I feel I understand what would happen if a ship could reach 95% of the speed of light, but how to get there is another thing. I've gotten the ship to about 50% using solar winds and a high beam particle accelerator being shot at sails (Which I found to be a very viable theory), but the rest I can't figure out. I don't even know if there is a way.

I think you’re on the right track with light or particle sail spaceships pushed by artificial beams – perhaps the best and most engineering detailed fictional account of this is in Rocheworld (note that all this post's book titles are wikipedia links). Another good, and newer one, though less central to the story, is in Accelerando.

 

Note that photon beams – microwave and longer up to a short distance, and visible or near visible band up to nearly any distance – are potentially as or more useful than massive particle beams. There are a lot of variations on this general idea, but in any case, separating the ship from the power and reaction mass sources is practically essential to the physically plausible design of a fast spaceship.

 

That said, and assuming an ability to aim a light or particle beam of much greater power (Rocheworld’s beam sources are gigantic, space-based solar-powered arrays orbiting close to Sol, with total power several powers of 10 greater than ever produced on Earth) with much better precision than is currently possible, there’s little limit to how close to the speed of light you could propel a ship. The problem is not available propulsive thrust, but that at such high speeds relative to the interstellar medium, damage and heating to the front of the craft becomes a difficult engineering problem. Some solutions involve massive ablative shields of, say, water ice, but as such spacecrafts’ may approach that of dwarf planets, the projected power requirements can rise to more than can be provided by a single star – pretty much the practical maximum for such designs. Assuming the engineering of some means of surviving and repairing damage from the occasional large (ie: pebble size) impactor, the problem is one of cooling. Spaceship striking the roughly 1 hydrogen molecule per cubic centimeter of interstellar space at .95 c, especially very wide sail-type design generate huge amounts of heat, but have no dense conductive or convective medium for cooling. An ablative design is one solution, but I’m personally intrigued by the idea of using the heat to pump large lasers to radiate it. Though in a different context, a fictional example of this can be found in Sundiver.

 

I’d be ignoring a generation or three of SF if I didn’t mention another high-speed spaceflight design idea, the Bussard ramjet. This scheme eliminates the need to carry reaction mass and solves the collision, and arguable the cooling, problems, by having the system ionize the interstellar medium, then both capturing and shielding the ship from it using giant magnetic fields. Though an older idea, as best I can tell, it’s a more difficult engineering challenge, perhaps so much as to be implausible. Though there are many SF stories about Bussard ramjets, my favorite is Tau Zero.

 

There are so many well-written fictional designs for high-speed spacecraft in SF that a writer nowadays might feel a bit like characters in Sundiver, where so much is available in galactic civilization’s great Library that engineering is more an act of library science than physical invention, resulting in a kind of galactic cultural ennui – but I find it all too much fun to be bothered with worries that any idea I have is likely to have been had and written about many times before me. When it comes to the SF genre, I’ve yet to find a really good writer, pro or amateur, who wasn’t also a voracious reader. :)

[modest]

The only problem, (which I forgot to mention earlier) is that the part about going 95% is that is would be on accident.

 

If the ship accidentally ventured into the ergosphere of a rapidly spinning black hole and lost part of its mass while there (perhaps because of tidal forces something gets ripped off the ship) it could exit with significantly more velocity than it entered. I believe it's called a Penrose process. It's like a gravity assist except that you borrow angular momentum from teh spinning black hole rather than linear momentum from, for example, a planet. And, it could happen by accident if the black hole were not visibly accreting matter.

 

~modest

[Eclipse Now]

I’d be ignoring a generation or three of SF if I didn’t mention another high-speed spaceflight design idea, the Bussard ramjet. This scheme eliminates the need to carry reaction mass and solves the collision, and arguable the cooling, problems, by having the system ionize the interstellar medium, then both capturing and shielding the ship from it using giant magnetic fields. Though an older idea, as best I can tell, it’s a more difficult engineering challenge, perhaps so much as to be implausible. Though there are many SF stories about Bussard ramjets, my favorite is Tau Zero.

 

Yahoo! Yeah, I read that like 30 years ago when I was 12-ish. That ship ran for a loooong journey! :phones::phones: (And IT was due to some sort of accident as well, but I don't remember what).

 

< I still remember the main hero was trained in martial arts, and 'easily deflected his opponents inexpert blows'. As a kid, it was one of the first times I'd read a story involving martial arts and often wondered how cool it would be to do Karate >

 

The beam somehow ignites the cloud, or supercharges it or something and either creates a disturbance which catches the sails and catapults the ship like a strong wind catching a sailboat, or generates enough power in an explosive manner flinging the ship. both of these would send the ship on its course, give or take a few light-years or so because of the nature of the cloud, and you wouldn't be able to steer the ship while its flying through space.

 

Just make sure there's an explanation as to why the ship doesn't just suddenly blow up! :evil:

[CraigD]

Though there are many SF stories about Bussard ramjets, my favorite is Tau Zero.

Yahoo! Yeah, I read that like 30 years ago when I was 12-ish. That ship ran for a loooong journey! :eek:;) (And IT was due to some sort of accident as well, but I don't remember what).

It’s been a long time since I read it, too, and I don’t have an electronic or paper copy at hand, but as I recall ...

 

SPOILER ALERT!

 

… the accident that launched the long journey of the Leonora Christine was that, passing through an unexpectedly dense bit of interstellar space – a small, previously undiscovered nebula – the systems that decelerate it are damaged so badly they must be repaired before the ship can decelerate.

 

(There are two main kinds of Bussard ramjets – ones that can orient their collector/deflector fields forward or backward, and have a single rocket motor which can be used to accelerate and decelerate, and ones that can only orient the field forward, and have separate accelerator and decelerator motors. The LC is of the second kind)

 

The crew have the necessary materials and tools to repair the damage systems, but can’t get to them, because it would be necessary to temporarily shut down the fields, and the ship would be impacted and heated to death if they did. So they plot a course for volume of space within the galactic disk with little interstellar material, accelerating so they can reach it within their lifetimes, only to discover that, when they reach it, at their increased speed, it’s still too dense to allow the field shut down. They plot a course out of the galactic disk, accelerating again, only to discover it’s too dense to allow field shutdown and repairs. They plot a course for deep intergalactic space, only to discover ... etc.

 

Due to their tremendously time dilation, they notice that, contrary to theoretical expectations, the universe is actually closed, and will in the far future cease expanding and collapse in a big crunch/bounce/bang. So they accelerate even more, increasing their time dilation (the title, “tau zero”, refers to the time dilation factor [imath]\tau = \sqrt{1-\left( \frac{v}{c} \right)^2}[/imath], which, as their v approaches c, is indeed approaching zero – an unusual use of the symbol [imath]\tau[/imath]) until the visible universe collapses into a big crunch. 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.

[CraigD]

If the ship accidentally ventured into the ergosphere of a rapidly spinning black hole and lost part of its mass while there (perhaps because of tidal forces something gets ripped off the ship) it could exit with significantly more velocity than it entered. I believe it's called a Penrose process. It's like a gravity assist except that you borrow angular momentum from teh spinning black hole rather than linear momentum from, for example, a planet. And, it could happen by accident if the black hole were not visibly accreting matter.

That’s a brilliant story idea! :phones: Not to cast any aspersions on SadBot and Theory5’s ignited nebula idea, which has some tremendously cool possibilities (eg: how long would it take? What would it sound like?), especially since SadBot’s the one doing the actual work of writing the story, but AFAIK, a Penrose process hasn’t been used in a major SF story, and writing a fictional first-hand account of a macroscopic non-Newtonian mechanical process is a physicist/hard SF writer’s dream! ;)

[SadBot]

I've really enjoyed the ideas! I don't even know what to do. I like the particle igniting storyline and the black hole... So now I just need to decide what to do. If I went with the black hole, which I admittedly know very little about the penrose process, how would the ship get damaged? Well, I am sure I could work something out with that. Lots to think about...

 

All great ideas, though. Thanks all for the great help!!

 

Any other suggestions are welcome. :phones:

[modest]

If I went with the black hole, which I admittedly know very little about the penrose process, how would the ship get damaged?

 

I can think of two directions you could go. Either the ship is damaged from tidal forces and loses ballast which would effectively be ripped off the ship into the hole, or the crew could calculate that their engines will not provide enough thrust to avoid being swallowed by the hole. At maximum acceleration the ship would still fall past the event horizon and the crew's inevitable death. 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.

 

 

If you go with a tidal force they effectively act to stretch the ship—pulling it apart. The longer the ship and the smaller the black hole the greater the force. Craig wrote a good post describing tidal forces near a black hole,

 

Spaghettification, atypical black holes, length contraction, graphs, and an excercise

 

and here's a page describing it from a first-person perspective,

 

BLACK HOLES by Ted Bunn

 

But, yes, it does seem necessary if you're going with a Penrose-process-like gravity assist for a significant amount of the ship's mass to somehow be lost into the black hole.

 

~modest

[SadBot]

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. 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

[freeztar]

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