07-26-2021, 07:29 PM | #11 |
Join Date: Aug 2007
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Re: Spaceships: How to take off?
Indeed 1 engine and then you get 9 Fuel Tank modules whihc would be 4.5 mps of Delta-V except for the table next to the Fuel Tank entry which explains that with 9 tanks you multiply Delta-V by 1.4. That gets you 6.3 and you have not only enough to get to orbit but enough for a vertical landing SpaceX style too.
That leaves 10 spaces and you must have a Control Room. Then you probably want 3 Armor systems to give you a decently durable hull. The remaining 6 spaces you can use for Cargo and you're HEDM shuttle can haul 30% of its' weight into orbit. That's why i rated it best. It's much better than any chemical rocket such as we have now. For Superscience drives you just take enough engines to add up to over 1 G and then one or more Power Plants to supply the needed energy.
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Fred Brackin |
07-26-2021, 09:47 PM | #12 | |
Join Date: May 2005
Location: Oz
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Re: Spaceships: How to take off?
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I did a study of the minimum cost of orbital launch using GURPS Spaceships, and concluded that far the cheapest means at TL10 is to use ground-orbit lighters propelled by limited-superscience fusion torch engines using water for their reaction mass. For the median human-habitable world (as produced by GURPS Space 4e), which has 0.81 gee surface gravity and an orbital speed of 4.15 mi/sec, one engine with normal thrust and one tank of water minimises the cost. In the case of the the highest-gravity habitable worlds (which have about 1.6 gee and 7.7 mi/sec) cost is minimised by one high-thrust fusion torch and four tanks of water. ____ ¹ Which is in Indistinguishable from Magic.
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07-27-2021, 01:14 AM | #13 |
Join Date: Jul 2008
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Re: Spaceships: How to take off?
The realistic answer is interplanetary drives and launch drives are different drives, and most likely are attached to different vessels. A ship with a high-impulse drive and an interface shuttle with a high-thrust drive.
If you must have a dual-purpose drive the least superscience option that's not economically disastrous like antimatter or environmentally disastrous like external fission drives is probably the fusion torch.
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I don't know any 3e, so there is no chance that I am talking about 3e rules by accident. |
07-27-2021, 01:25 AM | #14 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: Spaceships: How to take off?
The fusion torch has a power output of bit over 2 gigawatts per ton of thrust. Even if the radiation isn't a problem, they're going blast giant craters every time they take off.
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07-27-2021, 05:23 AM | #15 |
Join Date: May 2021
Location: Eastern Kentucky
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Re: Spaceships: How to take off?
Anyway, I know it is super science at this point in our history but solving the unified theory problem is not something completely unthinkable.
As soon as you solve that problem, one type of force can be turned into another type of force. This means those reactors that turn the propellor on an aircraft carrier and push it across the ocean can be used to turn a gravity propeller and push a ship up into space. For me, if I were going to start a space campaign, this is one of the breakthroughs I'd want to put in my history. Have a FTL drive is far less realistic than a unified theory breaththrough. In fact, I've long posited that just such a breaththrough is what we are waiting for to make our next "big" scientific jump. What I find less realistic to be honest is small craft jetting all over the solar system on reaction based fuel the way they do in the Expanse. I hope there is a gas station on every single corner in that solar system. |
07-27-2021, 06:05 AM | #16 | |
Join Date: Jun 2013
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Re: Spaceships: How to take off?
Errr, right. I was going off of MaryAnn's numbers rather than checking the books for myself, and misread "0.5 mps" as "0.5G."
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A possible way to avoid this would be to use a more traditionally-powered aircraft to get up into the sky, then break off and launch with your own drives, much like with the VSS Unity (and associated mothership VMS Eve) that recently took Richard Branson to the edge of space. So, you have a ship that's capable of traveling through space and typically uses a towing ship to help it get into space, but is capable of getting there under its own power if necessary. Of course, I agree that it makes a lot more sense to have separate space-travel craft and interface craft. The former would never touch down on a planet - rather, they'd park up in orbit, either docking with a space station or by themselves, and use interface craft to ferry personnel and goods/materials between the ship and the surface.
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GURPS Overhaul Last edited by Varyon; 07-27-2021 at 08:11 AM. |
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07-27-2021, 08:00 AM | #17 | |
Join Date: Sep 2008
Location: near London, UK
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Re: Spaceships: How to take off?
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On a world without atmosphere this is obviously more of a problem. In a setting I built some years ago, the rare cases of places with enough gravity that you couldn't just dock with them, but not enough atmosphere for wingborne flight (planets like Mercury), were dealt with via magnetic launch/landing tracks: fly your ship into the hole, and the magnetic field grabs it and decelerates it for landing. The numbers for aborts get a bit hairy (you need several ships in the pipe at once to get sensible traffic levels) but I think it's doable.
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07-27-2021, 08:44 AM | #18 | |
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Join Date: Sep 2004
Location: Southeast NC
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Re: Spaceships: How to take off?
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RyanW - Actually one normal sized guy in three tiny trenchcoats. |
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07-27-2021, 09:06 AM | #19 |
Join Date: May 2010
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Re: Spaceships: How to take off?
Yeah, I think they're in both Spaceships 7 and Spaceships 8, though, if you have either of those books. Spaceships 8 even has a worked example of an interface vehicle using that system. Otherwise, my personal preference is to use nuclear thermal designs like the Condor Spaceplane in Spaceships 2—the payload per trip is lower, but the fuel is both cheaper and safer.
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07-27-2021, 09:07 AM | #20 | |
Join Date: Jun 2013
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Re: Spaceships: How to take off?
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EDIT: Of course, the international community may well object.
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GURPS Overhaul Last edited by Varyon; 07-27-2021 at 09:34 AM. |
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