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System ships

Posted by: Nerroth - Wed Sep 29, 2004 12:21 pm
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Post System ships   Posted on: Wed Sep 29, 2004 12:21 pm
Hi!

A little different to the Starships debate, in this one I was wondering about people's thoughts on intra-system spacecraft, and by spacecraft I mean a vessel built in an orbital dock, and hence unrestrained by the need to take off and land, possibly carrying one or more atmospheric landers for descding to or ascending from other planets and moons in the solar system, possibly powered either by an M2P2 or ACMF (or other suitably powerful and efficient engine).

One issue as regards any large system craft approaching higher speeds, say .05 or .1c, which seems not to be addressed too often is whether there is a need to develop some kind of magnetic deflector to avoid impacts on the hull from fast-moving small objects either in a planet's orbit or near a dense asteroid field (sorry if I sound too trekish with all of this...), now apparently the M2P2 idea could be modified to act as a radiation shield to protect the crew - though as a fallback I'd still want a layer of lead or some more suitable material between my ship's hull and a nasty dose of radiation should the engine fail! - but could it also be used as a means to deflect smaller particles from the hull?

Also, since the vessel would be freed from the necessity to enter or leave orbit, what kind of hull design or composition would be ideal? (a big one, that!)

Gary


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Post    Posted on: Wed Sep 29, 2004 9:58 pm
.05-.1c is about what the current max speed of all theoretical starships except solar sail ones is now, so system ships are clearly alot slower. obviously you need to protect your ship from micrometeorites, and i agree that a magnetic shield of some sort is probably the best way. it'd really only be needed in orbit though, because there isn't much stuff anywhere else. even in the asteroid belt, the asteroids are very far apart, and there really isn't much in the way of space dust.

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Post    Posted on: Wed Sep 29, 2004 11:40 pm
Ok, so what would be the maximum rate of acceleration for such a system craft to reach, say, .05c, to avoid severe effects to the crew (we will assume for now that we must do without inertial dampers, sadly...), and say if such a vessel with standard 'cruising' speed of .05c were to set off for Mars or the Jovian system, how long would it take for the vessel to reach cruising speed (or indeed to decelerate to orbital velocity) and what kind of time scale are we talking as far as the overall travel time from Earth orbit to Martian or Jovian orbit?

As regards the asteroid belts the issue was more to do with avoiding damage caused by dust clouds surrounding the asteroids themselves (assuming such clouds or dense areas exist) should one wish at some stage to mine them for all their rocky worth... should it ever be necessary.

One other issue: Assuming the need to land on and take off from a moon or planet is catered for by one or more landing craft attached to the system ship, would the same kind of magnetic field presumably protecting the mothership form micrometeorites or left-over space junk need to be generated for the lander, and if so what power source would be sufficently powerful yet relatively lightweight to maintain such a field aound the lander (and allow it to successfully manage landings and takeoffs by itself)? Indeed, should such a support craft be designed to require only the means to reach escape velocity of the planets and moons other than Earth by itself, such as Mars or Europa, and leave any need to launch again from Earth to an additional earth-launched booster?


Gary


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Post    Posted on: Thu Sep 30, 2004 6:51 am
Hello, Nerroth,

you've started a discussion including several aspects forming a complex topic. I like that but this moment I am cosidering only one single aspect.

I would prefer spaceships never landing on and - as a consequence - never launching from planetary surfaces. Such spaceships can be specialized for interplanetary travels and missions. Then for launching and landing spacecrafts specialized for these purposes can be used. This would keep costs low.

Additionaly PERHAPS interstellar spaceships could be provided at orbits around the sun. But then the drives have to considered again. A spaceship specialized for interstellar journeys using solar sails has to launch from a solar orbit at a distance closer to the sun than Mercury whereas other interstellar specialized spaceships can launch from the outmost regions of the solar system using pulsed fusion drives. And these interstellar ships should carry interplanetary ships plus vehicles to land on and launch from exoplanets.

...



Dipl.-Volkswirt (bdvb) Augustin (Political Economist)

PS: System ships are merely an infrastructure or a traffic system...


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Post    Posted on: Thu Sep 30, 2004 5:39 pm
Nerroth wrote:
Ok, so what would be the maximum rate of acceleration for such a system craft to reach, say, .05c, to avoid severe effects to the crew (we will assume for now that we must do without inertial dampers, sadly...), and say if such a vessel with standard 'cruising' speed of .05c were to set off for Mars or the Jovian system, how long would it take for the vessel to reach cruising speed (or indeed to decelerate to orbital velocity) and what kind of time scale are we talking as far as the overall travel time from Earth orbit to Martian or Jovian orbit?


Well, the maximum speed achievable when accelerating from Earth to Jupiter at a decent rate, and then deccelerate in order to go into orbit around it, can be done quite easily.

Firstly, consider the distance from Earth to Jupiter - 400,000,000 miles (closest approach).

The best rate to accelerate is probably 1g - it's an obvious choice, and the best for humans.

So, how far can you accelerate for? At 400,000,000 miles, that's 200,000,000 miles of acceleration and decceleration. 200,000,000 miles is 320,000,000 km, or 3.2*10^11m.

Using the mechanics equation: v^2 = u^2 + 2as
v^2 = 2 * 1 * 3.2*10^11
v^2 = 6.4*10^11
v = 8 * 10^5 ms-2

The speed of light is 3 * 10^8 ms-2, and so as a fraction, it could realistically achieve 1/500, or 0.002c

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Post    Posted on: Wed May 18, 2005 2:52 pm
What the article "t/Space Offers an Option for Closing Shuttle, CEV Gap" ( www.space.com/spacenews/businessmonday_050509.html ) is reporting seems to tend to assist the idea of this thread a little bit:

Quote:
Under the t/Space plan, teams led by Lockheed Martin or Northrop Grumman would still build the CEV, but the vehicle would be designed solely to transport astronauts between Earth orbit and the Moon. The job of getting astronauts up to their Moon-bound CEV would fall to t/Space and an air-launched four-person capsule they have dubbed the Crew Transfer Vehicle, or CXV


I consider this only to be a possible germ but it is close to what I had in mind in my last post in this thread.



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Post    Posted on: Wed May 18, 2005 9:57 pm
Off Topic. I love the Buran icon there Nerroth.


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Post    Posted on: Sat May 16, 2009 4:57 pm
Might it be that system ships would have to have several different drives in parallel to switch between them?

Plasma drives for long distances and chemical ones for shorter distances for example?



What about it?



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Post    Posted on: Sat May 16, 2009 5:27 pm
Without VASIMR or Nuclear, we'll probably be limited to that option. For example: it doesn't really make sense to use anything other than Chemical for LEO-to-Luna, unless you have another high thrust option available.

1/5g is a figure I've seen a lot in regards to other drive systems. That would be good enough for a Lunar mission, so we could drop chemical except for launch from a bodies surface.

I'd shape it as a sphere. Best volume/surface area ratio, so we don't need to have as much shielding. But the shape also depends on whether you want artificial gravity.

If you can sustain 1/5g, though, you can drop the centrifuge.


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