Questions on space travel for a sci-fi story

[Astronuc]

GCR is Galactic Cosmic Radiation, and you can probably find discussions in the Astronomy and Cosmology sections if you go to that forum and search for GCR. Basically it's high energy particles traveling through space like solar wind, but they can be more damaging because of spallation reactions in the structure of the craft. Then there is the X-ray/gamma-rays from secondary radiation.

No I mentioned 100 MT (100,000 kg) where M = metric. Metric ton is commonly used in the nuclear industry, but I suppose it's easy to confuse with megaton.

According to special relativity though, there is a mass increase associated with matter approaching the speed of light.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html#c3

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/relcon.html#c1

In fact, hyperphysics is a good source to browse for topics on physics and some of the math behind it.

As for a mission scenario - you might want to look into the current status of exosolar planets, e.g. http://www.everything-science.com/content/view/196/1/

 

[StarkRavingMad]

Thank you for those links.

I had assumed that increase in mass was the result of force, not actual mass. See... told you I was a Pakled when it came to this stuff.

 

[Astronuc]

Well, as others pointed out, one can take substantial license with reality in Scince Fiction, with Faster Than Light (FTL) travel, or worm holes, and in the extreme, Douglas Adams has a character who pops in at the End of the Universe (end of time as we know it) from the beginning of the universe (Big Bang).

One has to decide what contraints one wishes to impose on the technology of space travel. Either one goes with real phyics, in which case, interstellar travel takes a long time, or one goes with being able to pop anywhere at anytime, or anything in between.

 

[StarkRavingMad]

Astronuc, I'd like to send you a PM sometime giving a few of the details, just to see if they sound "feasible" in a sci-fi sense. I am going for that middle ground between impossible and grounded. :)

I don't want to post them on a public forum on the off chance another writer is surfing and steals them, because I think they are fairly unique, at least as far as things I have read and watched.

 

[Astronuc]

Sure - all PMs are treated as confidential.

 

[Ivan Seeking]

You missed that just a mite. Roddenberry's thought throughout the creation of the show was of Horatio Hornblower, not Dillon.

Interesting. Where did you hear that?

It could be that Kirk was sold to the studios as Dillon, but I know this idea was in play for a time and I think it was attributed to Rodenberry. At the time westerns ruled the day, and the networks wanted a western in space.

This was all discussed in a fairly recent Trek anniversary special, with Jonathan Frakes as the host.

Did you happen to see the show about how Trek changed the world?

 

[StarkRavingMad]

I have another question about sci-fi and space...

On a particular episode of Babylon 5, Dr. Franklin gave a rather graphic and none too pleasant description of what happens to someone when they are spaced out an airlock.

But the absolute zero temperature and lack of pressure did not stop Farscape, Cowboy Bebop, and one of the Star Wars novels (among other places I am sure) from having a scene with our hero floating between ships in space without any protection. The Star Wars novel even gave the stunt a nickname, "coldshirting", implying that such a thing is done often enough to HAVE a name.

Now Farscape had the decency to put John into instant hypothermia at least. He had to be rushed to the med bay. The scene from the Cowboy Bebop anime was in an asteroid, where I guess it could be argued that there may be a very thin atmosphere and some gravity. Both seemed too hoaky to me, though.

So the ultimate question is... is it possible for a human being to survive in space AT ALL without protection. Would the nasty effects of your organs exploding and freezing happen instantly, or would you actually have a few seconds?

 

[Danger]

Interesting. Where did you hear that?

Hey, Ivan. I saw it in several references, and in Roddenberry's own words. While I can't remember for sure, the most likely books are 'The Making of Star Trek' (I forget the author), 'The World of Star Trek' by David Gerrold, or the newer, darker behind-the-scenes which I think was written by Robert Justman and Herb Solow. I also have a book which I think is called 'The Last Interview' with Roddenberry. I'll try to check for sure, but it will involve a trip to my mother's place where all of my books still reside.

Did you happen to see the show about how Trek changed the world?

I'm pretty sure not. Until I moved in with W several months ago, I never got cable. It doesn't sound like the kind of thing our local channels would air.

is it possible for a human being to survive in space AT ALL without protection. Would the nasty effects of your organs exploding and freezing happen instantly, or would you actually have a few seconds?

Explosive decompression is something that happens to vehicles, not the people in them. An unprotected human can survive in vacuum for at least several seconds. You can bet that his ears will pop, though.

 

[StarkRavingMad]

Got another question about how g-forces would work in space, if they do.

Without artificial gravity on a spaceship... what would be the effect on a crew member as the ship accelerated? ... toward lightspeed?

BTW Astronuc, I sent you a PM.

 

[Rach3]

Got another question about how g-forces would work in space, if they do.

Without artificial gravity on a spaceship... what would be the effect on a crew member as the ship accelerated? ... toward lightspeed?

BTW Astronuc, I sent you a PM.

Depends on how they accelerated; if at nearly 9.8m/s^2, it would be indistinguishable from standing on the surface of the earth. If significantly higher, their would be very dangerous cardiovascular effects (look up g-forces in fighter pilots). If significantly lower, they'd face bone loss and all the other negative effects experienced on space stations (look up ISS and health). So if they had any common sense, they'd be accelerating at nearly 1g. In real life of course, no rocket can sustain this kind of acceleration for long - hence the proposals for spinning spacecraft (centripetal acceleration).

 

[Rach3]

But the absolute zero temperature and lack of pressure did not stop Farscape, Cowboy Bebop, and one of the Star Wars novels (among other places I am sure) from having a scene with our hero floating between ships in space without any protection. The Star Wars novel even gave the stunt a nickname, "coldshirting", implying that such a thing is done often enough to HAVE a name.

Space is not a vacuum, and it does have a temperature (e.g., see wiki's article http://en.wikipedia.org/wiki/Interplanetary_medium) . Regardless, near-vacuums are very good thermal insulators - they're used in thermos bottles. No "instant hypothermia".

 

[StarkRavingMad]

Actually Wikipedia has been my best friend for a while now. It's not my only source, but I always hit it first.

After I posted the question about humans surviving space, I found this...

http://en.wikipedia.org/wiki/Human_adaptation_to_space

The way I understand it, there is not enough out there to create convection or conduction, so heat loss would be by radiation alone.

But the sunburn after just a few seconds sounds just as bad. Ignoring temperature, it looks like you'd have about 10-15 seconds before decompression sickness set in and you blacked out.

A minute and a half till death... but who knows how dehydrated you'd be, assuming you have SOME kind of UV protection or the whole point is moot (unless you're way outside of a solar system maybe).

The fact that you wouldn't be cold is so wild. But actually you may be assuming you were blasted out of a pressurized cabin.

On the acceleration issue... it looks like artifical gravity is the only way to go. It doens't look like a human could survive the kind of acceleration you'd need to get to relativistic speed.

 

[Astronuc]

So the ultimate question is... is it possible for a human being to survive in space AT ALL without protection. Would the nasty effects of your organs exploding and freezing happen instantly, or would you actually have a few seconds?

Basically one would suffocate in a matter of seconds, eyes and soft tissue would expand (bulge) and it would probably feel like one's insides are coming up through one's throat. It wouldn't be pleasant!

Heat transfer by radiation is slow, since the temperature of the skin is say about 25°C, so instant hypothermia is not possible. Use the Stefan-Boltzmann equation.

 

[Hootenanny]

Basically one would suffocate in a matter of seconds, eyes and soft tissue would expand (bulge) and it would probably feel like one's insides are coming up through one's throat. It wouldn't be pleasant!

Heat transfer by radiation is slow, since the temperature of the skin is say about 25°C, so instant hypothermia is not possible. Use the Stefan-Boltzmann equation.

An objective and clinical analysis to a gruesome and pretty disturbing death. The mental images are not pretty .

~H

 

[StarkRavingMad]

Moving on to something a little less icky...

Considering that it's not just planets revolving around suns, but all of the stars of the galaxy revolving around the core like a frisbee... Is it conceivable to park a space station in deep space away from a solar system to "anchor" it?

Does it sound conceivable to be able to make all of the calculations to keep the station in position relative to the systems around it? How fast would it have to be propelled to keep up with the other moving systems. Or would it still get moved without the need for its own thrust along with the gravimetric forces already holding the galaxy together?

 

[Astronuc]

A space station could conceivably be 'parked in orbit', much like a satellite in geostationary or geosynchronous orbit.

http://en.wikipedia.org/wiki/Geostationary_orbit

http://en.wikipedia.org/wiki/Geosynchronous

This is just a start, but I would recommend cross-referencing with other sites.

There are also nodes where the gravitational fields of two bodies balance, e.g. L1 node.

See this paper
http://www.andrews-space.com/images/videos/PAPERS/AIAA%202005-6739%20Solar%20Electric%20Tug.pdf

http://exploration.nasa.gov/documents/reports/cer_midterm/Andrews.pdf

http://exploration.nasa.gov/documents/reports/cer_midterm/Boeing.pdf

They contain some relevant information to local space exploration.

 

[StarkRavingMad]

Powreful. Thank you. Are you ever going to reply to my PM? :shy:

 

[StarkRavingMad]

A space station could conceivably be 'parked in orbit', much like a satellite in geostationary or geosynchronous orbit.

Reading this and the links again, I may not have asked the question clearly.

I understand how to attain orbit around a planet. Basically you gain enough inertia to move at a speed that balances you with the planet's gravity so that you neither escape or get pulled in.

But what I am curious about is a space station in DEEP space, far from any planets to anchor it. Would there be a way orbit a system the same as a planet? Does a system have a collective gravitational field that extends completely around it in the same manner?

Or would such a feat require constant calculations to adjust the station's vector, so it keeps moving in a path relative to the systems around it?... (I may have just answered my own question.)

 

[Mk]

But what I am curious about is a space station in DEEP space, far from any planets to anchor it. Would there be a way orbit a system the same as a planet? Does a system have a collective gravitational field that extends completely around it in the same manner?

The objects move around a common barycenter. Yes, systems have collective gravitational fields, but it is not uniform. Barycenter animations

 

[StarkRavingMad]

A question to clarify this issue with gravity and thrust...

It seems like a ship would definitely need some kind of local gravity to compensate against the thrust required to accelerate toward lightspeed in a short timeframe. Otherwise the crew would all be flattened against the hull, passed out.

Would this gravity only be required when thrust is being applied? IOW could it theoretically be dropped when the ship is in free-fall, moving at any given speed through space, but with no further acceleration?

 

[Danger]

It certainly could be turned off, but it wouldn't be a good idea as long as it isn't a serious power hog. There are serious medical problems associated with long-term freefall, such as bone decalcification and circulatory issues, not to mention the commonality of space-sickness. Also, why go through the inconvenience that it causes for gravity-acclimated people? Just simple stuff like having a shower or using a toilet are complicated, and that's nothing compared with trying to make a decent Baked Alaska.

 

[StarkRavingMad]

It certainly could be turned off, but it wouldn't be a good idea as long as it isn't a serious power hog.

Thanks. That is what I figured. I wouldn't think it would normally be turned off either, but I was wondering if it could without endagering the crew in emergencies.

I wouldn't imagine it would hog that much power in a space age setting. The generators would probably draw more power compensating against acceleration than just maintaining 1 G in freefall. I'm considering having some kind of gravity harness or chamber rather than making a generator try to apply equal gravity across an entire ship during high speed maneuvers, or during the acceleration burst to get from escape velocity to c.

What would happen to a body under the stress of prolonged double-digit g-forces? Would they just pass out, or would there be physical damage?

 

[Danger]

What would happen to a body under the stress of prolonged double-digit g-forces? Would they just pass out, or would there be physical damage?

'Double-digit' covers a lot of territory. To start with, only people in very good physical condition can handle 10 g. Secondarily, the effect of acceleration depends upon in which direction it's applied. Bird-driver terminology refers to it as 'eye-balls in', 'eyeballs-up', etc., dependent upon the vector. 'Eye-balls in', for example, means positive acceleration in the direction that the pilot is facing. It comes from the fact that your eyes move backward into your head in that situation. You can extrapolate the rest.
A positive acceleration will impose black-out, wherein there isn't enough pumping force from your heart to get the blood to your brain against gravity. Negative acceleration produces red-out, which happens when too much blood is forced into your head.
I believe, although there are others here who know a lot more about it, that NASA or US Air Force shock suits can keep the pilot conscious up to about 18 g (I'm tired of italicizing that). Even at that, more than a few seconds, or minutes at most, is very hazardous.
If I'm not mistaken, this is an area in which Russ Watters is very knowledgeable. Fred Garvin can probably weigh in significantly as well. I know that Integral is also a pilot, but I'm not sure if he has had military or aerobatics experience.

 

[russ_watters]

Answer to pm/thread...

The question atm is about the extent of heavy g-forces on a human body in space. The acceleration that we're talking about is pretty huge... the amount of thrust needed to push a ship from escape velocity to relativistic speed, like .3c. So it's kind of hard to use numbers.

How much g-force are we talking about here, and in the absense of some kind of gravity compensating against that force, what would it do to a body?

Early astronauts took something like 12-15 g for a few minutes during re-entry. Regardless of the intensity, though, the effects are the same (just multiplied by higher intensity): Primarily, your muscles, particularly your heart, abds, and your diaphram have to work harder to do their jobs. 2 or 3 g might be analogous to a brisk walk, 5-7 to good run, and 12-14 an all-out sprint. And the only way to handle more than about 8 for more than a few seconds is in the prone position in an ergonomic couch, with a g-suit. Your heart simply isn't capable of working against that much pressure and you'll pass out from lack of oxygen to your brain, otherwise.

So .3C...

At 10g, that's a little more than a month to reach that velocity. I doubt even in an induced coma, with a breathing apparatus and IV for food a person could survive that. You'd probably die of a heart attack in a day (as if you had tried to run 6 marathons in a row, at 4 hours each).

I would guess a person in good shape could probably handle 2g for a few months and 1.5 indefinitely. That kind of acceleration doesn't help you if you are looking to travel within the solar system in days, but it would do you just fine if you are trying to travel to the nearest stars in a human lifetime.

 

[StarkRavingMad]

I was thinking more of science fiction timeframes, where a ship accelerates from supersonic to sublight in a matter of minutes and then freefalls the rest of the way until it needs to adjust course.

Actually now that I think about it... wouldn't adjusting course by more than a few degrees while traveling at something like .3c (in the absense of some kind of internal gravity generator) create ungodly g-forces, too?

 

[StarkRavingMad]

From rereading all of this, including the links, I've come to the conclusion that interstellar travel at the kind of speed in science-fiction is just not possible without a localized gravity well.

It seems that accelerating from mach 6 to .3c in under a minute would create more thrust than a human(oid) body can handle. You'd need a compensator pulling in the opposite direction to equalize so that the passengers are constantly experiencing somewhere around 1G.

Is that safe to say?

 

[DaveC426913]

From rereading all of this, including the links, I've come to the conclusion that interstellar travel at the kind of speed in science-fiction is just not possible without a localized gravity well.

It seems that accelerating from mach 6 to .3c in under a minute would create more thrust than a human(oid) body can handle. You'd need a compensator pulling in the opposite direction to equalize so that the passengers are constantly experiencing somewhere around 1G.

Is that safe to say?

Yep. That's safe bet.

But what I am curious about is a space station in DEEP space, far from any planets to anchor it. Would there be a way orbit a system the same as a planet?

Something to keep in mind.

1] When you get out into the outer solar system, g-pull from the Sun is so weak, you don't really have to worry about orbits for short term use, like a spaceship. You can basically just park. Sure, you'll fall inward, but really slowly. It would be irrelevant, especially since there's be nothing nearby to even notice your drifting.
2] Pluto takes 260+ years to orbit. Park a space staion out there, and you don't have to give it much motion in order for it to be in a stable orbit. Go out a few multiples of Pluto's distance and it would be centuries before you'd noptoce let alone care whether you're in a stable orbit. Again, your tangential motion is so small, you're practically parked.

 

[Astronuc]

I agree with DaveC. However, one would have to avoid comet type orbits with shorter periods.

The Voyager craft are 'leaving' the Solar System.

Voyager 2:
Voyager 2 has visited more planets than any other spacecraft , swinging by Jupiter, Saturn, Uranus and Neptune. Voyager 2 was deflected downward by Neptune and is heading southward below the plane of the planets. With a somewhat lower speed than Voyager 1, it is about eighty percent as far from the Sun.

Voyager 1:
Voyager 1 is the most distant human-made object in the universe, At the beginning of 2005, the spacecraft was about 94 times as far from the Sun as is Earth. It was deflected northward above the plane of the planets' orbits when it swung by Saturn in 1980 and is now speeding outward from the Sun at nearly one million miles per day, a rate that would take it from Los Angeles to New York in less than four minutes. Long-lived nuclear batteries are expected to provide electrical power until at least 2020 when Voyager 1 will be more than 13 billion miles from Earth and may have reached interstellar space.

http://www.nasa.gov/vision/universe/solarsystem/voyager-interstellar-terms.html
http://www.nasa.gov/vision/universe/solarsystem/voyager_agu.html

I was thinking more of science fiction timeframes, where a ship accelerates from supersonic to sublight in a matter of minutes and then freefalls the rest of the way until it needs to adjust course.

Once a spacecraft shuts down its propulsion system, it coasts. If it has achieved escape velocity, it will keep on traveling.

As for large accelerations, it would be difficult for humans to function with an acceleration much greater than 1g. Think about 2g, a human body of mass 75 kg (165 lbs) would have a 'weight' of 330 lbs - not too many humans could deal with that on a prolonged basis - muscle fatigue/strain would like result in short time.

Science fiction (e.g. Star Trek) can invoke some anti-gravity or zero-gravity or constant gravity field, which as far as we know in not possible in our reality. At present, we understand that 'gravity' requires 'mass', and lots of it to generate a field of 1 g. Mass requires a force to cause it to accelerate, and any force applied over a distance requires energy, and to make it happen, requires lots of momentum.

http://en.wikipedia.org/wiki/Standard_gravity#Strongest_g-forces_survived_by_humans - I am not sure how valid these are, but I they are rather exceptional examples.

This looks interesting
http://www.saferparks.org/are_rides_safe/dynamic_force/gforce_2002.php

One could volunteer to test the effects of acceleration
http://news-service.stanford.edu/news/2002/march20/centrifuge-320.html