Spaceships and Science fiction


by SHISHKABOB
Tags: fiction, science, spaceships
Ryan_m_b
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#109
Feb22-13, 06:22 PM
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Quote Quote by Traz 0 View Post
From the Robert Heinlein wiki:

Heinlein himself stated - with obvious pride - that in the days before pocket calculators, he and his wife once worked for several days on a mathmatical equation describing an Earth-Mars rocket orbit, which was then subsumed into a single sentence of the novel Space Cadet.
I'm not sure how that applies to the quoted sentence...
Traz 0
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#110
Feb22-13, 06:42 PM
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Quote Quote by Ryan_m_b View Post
I'm not sure how that applies to the quoted sentence...
and previously (I don't know how to multi quote on my phone):

GTOM said, roughly:

"I read about orbital mechanics, I think it's a must have for science fiction writers ..."

See, my point was, Robert Heinlein, a pretty famous science fiction writer, seems to have agreed with both GTOM and you about orbital mechanics vis a vis SF writing, in a time when doing so took a lot more work.

I thought the thread I was following there was pretty clear ...
Riemann Metric
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#111
Mar4-13, 06:26 PM
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Quote Quote by Traz 0 View Post
Well, I certainly wouldn't want to live downwind of a surface launch.

As far as a Project Orion space drive, I suppose that its feasibility is partially an engineering problem, and partially political, i. e., who would I trust in possession of hundreds of nukes in space, how they could be secured, etc. Barring an alien invasion or a dino-killer space rock with our name on it, my vote would be, uh, no thanks.
I'm sure there are many elegant solutions to space travel than blowing up a bunch of bombs behind a plate to launch a spacecraft at high speed-take solar sails or magnetic acceleration cannons/mass drivers, for instance. The only issues we have with these are slow acceleration+microasteroids vs. tremendous forces and huge momentary accelerations.
Traz 0
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#112
Mar4-13, 08:02 PM
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Quote Quote by Riemann Metric View Post
I'm sure there are many elegant solutions to space travel than blowing up a bunch of bombs behind a plate to launch a spacecraft at high speed-take solar sails or magnetic acceleration cannons/mass drivers, for instance. The only issues we have with these are slow acceleration+microasteroids vs. tremendous forces and huge momentary accelerations.
I'm sure there are more elegant solutions too.

In the novel<I> Footfall </I>, the problem to be solved wasn't spaceflight, per se. The invaders had occupied Earth, had surveillance ships in orbit, and a giant, well-protected mothership that was all but invulnerable. Engaging the enemy required a truly massive ship of our own that could sustain a great deal damage from kinetic and directed energy weapons. It also had to be built in secret, on earth, in a hurry, without a research program or orbital construction.

As far as stopping a dino-killer rock in a hurry, it's not inconceivable that we might have to substitute quick and dirty for elegant in certain scenarios. It certainly happens in the real world.

In 1992, I was managing a project to convert a government agency's antiquated applications and data to modern hardware, and there were a number of files that were weird for some reason I can no longer recall. I diagramed as general algorithm that could read any such file and create the data structure and conversion code needed, and gave it to a programmer. Rather than write that application, he looked at the files, found there were only 20 or so unique types, and wrote 20 or so separate programs. I have a strong preference for elegance in all things, and his solution pissed me off. But. The project had been underbid, we were behind schedule, and every day late cost my company money. His way <I> was </I> faster, and assuming we never needed to do the same type of conversion again, better.

Still, I'm not advocating <I> Project Orion</I> as a space travel solution, by any means, and I hope it didn't seem like I was.
Riemann Metric
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#113
Mar5-13, 04:44 PM
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Well, who knows...maybe something that seems unorthodox like Project Orion could inspire something that really does work. As it is said, necessity is the mother of invention, and I fear our efforts towards something we think we don't need will be rather negligible until our views change.
lpetrich
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#114
Mar25-13, 08:55 PM
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Isaac Asimov, in "Future? Tense!" from From Earth to Heaven described how a science-fiction writer in 1880 might write stories involving cars.
"The automobile came thundering down the stretch, its mighty tires pounding, and its tail assembly switching furiously from side to side, while its flaring foam-flecked air intake seemed rimmed with oil." Then, when the car has finally performed its task of rescuing the girl and confounding the bad guys, it sticks its fuel intake hose into a can of gasoline and quietly fuels itself.
While a car as a mechanical horse seems almost too silly for us to take seriously, lots of visual-media science fiction has similar absurdities about its spaceships.

I recall when Gene Roddenberry was once asked about some of them, like never seeing spaceships upside down. He responded that that was to avoid unnerving an Earthbound audience, and that's why explosions in outer space make sounds. A soundless explosion is correct, but it would make many watchers wonder what happened to their TV's' sound.

Some Star Wars battleships look more like they could be floating than flying, with a hull and a superstructure on one side of it, the crewmembers' upward direction.

A lot of the space combat in the Star Wars series looks like it could have come out of WWI and WWII dogfights -- the fighter spaceships behave too much like airplanes.

IA also imagined:
There could be the excitement of a last-minute failure in the framistan and the hero can be described as ingeniously designing a liebestraum out of an old baby carriage at the last minute and cleverly hooking it up to the bispallator in such a way as to mutonate the karrogel.
Some Star Trek episodes are full of that sort of thing, something that some fans and critics have named "treknobabble".
GTOM
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#115
Oct28-13, 06:18 AM
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Can we return to recon a little bit?

Ryan you said, that a really big battleship could carry a neutrino detector.
I read that a neutrino can easily go through the entire Earth.
Ok, you can determine whether something with a reactor is close or not, but can you possibly get any accuracy needed to target?

While you cant become invisible in space, how about a smoke screen like application, once you dont need to use the thrusters (you might still be able to do a tiny course change with magnetic fields), sorround your ship with black canvas, metallic nets, chaff? You dont have to be in the middle of this. Yes they will know roughly where you are, but i almost hit it is unsatisfactory... Probably you dont have a second chance to fire, or offer a barrage strong enough.
The concealed one could still see with small outside probes.

Also planetary defences have much better options to conceal a cannon, or orbital craft can redirect its waste heat toward the planet.
Ryan_m_b
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#116
Oct28-13, 10:47 AM
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Quote Quote by GTOM View Post
Ryan you said, that a really big battleship could carry a neutrino detector.
I read that a neutrino can easily go through the entire Earth.
Ok, you can determine whether something with a reactor is close or not, but can you possibly get any accuracy needed to target?
Sure neutrinos fly through the Earth and a lot more. But detectors can snatch a tiny percentage of them because a very small number will, statistically speaking, hit an atom.

Quote Quote by GTOM View Post
While you cant become invisible in space, how about a smoke screen like application, once you dont need to use the thrusters (you might still be able to do a tiny course change with magnetic fields), sorround your ship with black canvas, metallic nets, chaff? You dont have to be in the middle of this. Yes they will know roughly where you are, but i almost hit it is unsatisfactory... Probably you dont have a second chance to fire, or offer a barrage strong enough.
The concealed one could still see with small outside probes.

Also planetary defences have much better options to conceal a cannon, or orbital craft can redirect its waste heat toward the planet.
There's no stealth in space because your craft will be vastly hotter than the background. If you've got a power source like a nuclear reactor it means that your craft is going to have a spot in it hundreds of degrees hot. Even just at zero degrees C you will be hundreds of degrees hotter than the background.

This is a good article on the subject: http://www.projectrho.com/public_htm....php#nostealth
GTOM
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#117
Oct29-13, 10:52 AM
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"This is a good article on the subject: http://www.projectrho.com/public_htm....php#nostealth"

I read it already. But i didnt intend to hide my vector.

"sorround your ship with black canvas, metallic nets, chaff? You dont have to be in the middle of this."
"Yes they will know ROUGHLY where you are, but i almost hit it is unsatisfactory... "

"If you've got a power source like a nuclear reactor it means that your craft is going to have a spot in it hundreds of degrees hot."

So I sorround the ship with a light weighted, but opaque canvas. It will be heated all around to a pleasent degree. So where is the ship exactly in a large (but light) cube? Where should you aim if you want to actually hit it?

Of course it will the transparent to neutrinos (and i have to send out at least recon stuff communicating with wires).
But putting a neutrino detector to a battleship?
http://en.wikipedia.org/wiki/Sudbury...no_Observatory
And you have to shield it from your own reactor if you dont run with chem fuel.

Well, I dont really think this is viable, but at least it will be pretty hard to build such a spacecraft.
Ryan_m_b
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#118
Oct29-13, 11:08 AM
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Quote Quote by GTOM View Post
So I sorround the ship with a light weighted, but opaque canvas. It will be heated all around to a pleasent degree. So where is the ship exactly in a large (but light) cube? Where should you aim if you want to actually hit it?
Aside from the problem of how do you see where you're going now there are going to be hotspots suggesting where you are. Even if not I can't see you dragging around a big enough canvas than an enemy couldn't just shoot a missile through that has a shaped charged and is smart enough to quickly locate you and explode in that direction.

Quote Quote by GTOM View Post
Of course it will the transparent to neutrinos (and i have to send out at least recon stuff communicating with wires).
But putting a neutrino detector to a battleship?
http://en.wikipedia.org/wiki/Sudbury...no_Observatory
Lol you're talking about huge military space craft with nuclear reactors and you have a problem with fitting a neutrino detector in if you're handwaving away the technical difficulties of the former you should at least be consistent with not handwaving away other difficulties.

Besides which looks like there are efforts to shrink the size of detectors:
http://minnesota.publicradio.org/dis...trino-detector
GTOM
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#119
Oct29-13, 02:41 PM
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" if you're handwaving away the technical difficulties of the former you should at least be consistent with not handwaving away other difficulties."

I carried a tent many times but not a rad suit (shielding from your own reactor).

Otherwise OK i just surrender.
Thanks for the article Ryan, it is always good to read about new developments. :)
GTOM
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#120
Dec21-13, 03:06 AM
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" http://www.projectrho.com/public_htm....php#nostealth "

"The maximum range a ship running silent with engines shut down can be detected with current technology is:

Rd = 13.4 * sqrt(A) * T2

where:

Rd = detection range (km)
A = spacecraft projected area (m2 )
T = surface temperature (Kelvin, room temperature is about 285-290 K)

If the ship is a convex shape, its projected area will be roughly one quarter of its surface area."

An example : http://en.wikipedia.org/wiki/Chelyabinsk_meteor

"The United States space agency NASA estimated the diameter of the bolide at about 17–20 m and has revised the mass several times from an initial 7,700 tonnes (7,600 long tons; 8,500 short tons),[10] until reaching a final estimate of 10,000 tonnes"

Ok. Diameter 17m, radius half.

A ~ (17/2)^2*pi ~ 227m2 (*4 /4)

Surface temperature : (average lunar temperature?) 250 K

So Rd = 12 617 655 km...

If i decrease surface temperature to 40K (lunar minimum) it is still 323 026 km, Earth to Moon range.
And they can browse the whole sky in 4 hours...

"The Chelyabinsk meteor was a near-Earth asteroid that entered Earth's atmosphere over Russia on 15 February 2013 at about 09:20 YEKT (03:20 UTC), with an estimated speed of 18.6 km/s "

If i ignore speed gained by Earth'as gravity, just multiply 18,6 with four hours, it is still below that claimed distance.

What did i miss? They missed the meteor, there wasnt last minute warning, please get away from the windows.


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