The Most Optima All Aroundl Gravity Defying Spacecraft Shape Is....

[Spacescifi]

 

 

In scifi sometimes spacecraft have the ability to defy gravity by being weightless on a planet. For the sake of discussion, we will allow the the ability to defy a planet's gravity only (still will feel acceleration from engine thrust). Also has the ability to toggle this on or off, the weightlessness inside gravity wells.

Implications of gravity defiance: You do not need orbital velocity to reach space, and your escape velocity is literally however fast you wanna go and however long you want it to take with a given rocket engine.

What I am not sure about is the optimal shape for a spacecraft that can defy gravity like the OP.

Shapes available:

Cylinder: Classic rocket shape would still work, although the urgency to reach space is not longer as much, given the fact that gravity cannot pull you back down so long your gravity defiance is on.

Saucer: This has one advantage, namely for reentry, it slows the ship down faster, and when used in combination with gravity defiance, you can slow down on reentry even FASTER.

Sphere: You can rotate faster than any shape in space or in atmosphere. I am not sure what advantage this really serves unless you need a spacecraft that is exceptionally maneuverable.

Extra: The gravity defiance is a free resource, the rocket engine and spacecraft parts are real using real rocketry and thus not free. So given the costs and resources involved, what would be the most optimal spacecraft shape for escaping a planet and then traveling in space and also for reentry?

I like the saucer shape, but I have a hard time seeing a guy at NASA letting it through because his superiors will say they save money with the rocket shape due to less drag. But a NASA guy who was a Star Trek fan would push for the saucer shape and may either get demoted or lose his job in the process. That's despite the fact that I think saucers look awesome.

 

Your thoughts?

 

 

Edited September 15, 2019 by Spacescifi

[Rakaydos]

Sphere of density below that of air, able to ascend/descend like a blimp by adjusting how much gravity is being offset.

[kerbiloid]

Spoiler

 

[GluttonyReaper]

Cube - if you're spending most of your time in space, and ascent is incredibly trivial, may as well just ignore aerodynamics, right? Basically just build a flying house - not the most comfortable, but dirt cheap to make, so you can make loads of em, which is pretty much the major advantage of discovering a method of escaping Earth's gravity with almost no effort. 

[YNM]

33 minutes ago, GluttonyReaper said:

Cube - if you're spending most of your time in space, and ascent is incredibly trivial, may as well just ignore aerodynamics, right?

Hmm, Vogon Constructor Ship...

[Terwin]

The ideal hull shape is largely defined by your intended purpose:

A fully reusable bulk carrier with a low-thrust engine like an ion drive would be most efficient as a skeleton with attachment points for each container, having barely enough strength to keep them from blowing away in a strong wind for the take-off/landing portions.

For transporting a large bulk of habitable volume, you will probably want a spherical area for habitation, providing the most space per weight of the air shell.

For high-speed ships like interceptors or private transports, you will want a classical rocket shape, possibly a rocket-jet with an air-breathing first stage/tug boat.

(Gravity negation greatly aids in recovering spent boosters as they can soft-land(or hover) with a much lower mass-penalty)

Edited September 16, 2019 by Terwin
comma

[Spacescifi]

4 hours ago, GluttonyReaper said:

Cube - if you're spending most of your time in space, and ascent is incredibly trivial, may as well just ignore aerodynamics, right? Basically just build a flying house - not the most comfortable, but dirt cheap to make, so you can make loads of em, which is pretty much the major advantage of discovering a method of escaping Earth's gravity with almost no effort. 

 

Yes, it would work,  especially if you did not pressurize the whole inside of i (air pressure loves to break corners). You would either need inflatable habitat modules inside (cheaper and less mass) or separate pressurized rooms (most mass required).

 

1 hour ago, Terwin said:

The ideal hull shape is largely defined by your intended purpose:

A fully reusable bulk carrier with a low-thrust engine like an ion drive would be most efficient as a skeleton with attachment points for each container, having barely enough strength to keep them from blowing away in a strong wind for the take-off/landing portions.

For transporting a large bulk of habitable volume, you will probably want a spherical area for habitation, providing the most space per weight of the air shell.

For high-speed ships like interceptors or private transports, you will want a classical rocket shape, possibly a rocket-jet with an air-breathing first stage/tug boat.

(Gravity negation greatly aids in recovering spent boosters as they can soft-land(or hover) with a much lower mass-penalty)

 

Thanks.

So saucers are out? Like if that Trekkie Nasa guy keeps it up encouraging some variation of the enterprise he may get demoted?

The irony is ihat I probably should have stuck with the theory of general relativity, which claims that acceleration and planet gravity are identical. Which means gravity negation would cancel out all g-force during acceleration.

Which means you can finally get the classic trek bridge while the engines are firing in the back.... only difference being that they are totally weightless unless they land the ship on a planet and toggle gravity negation off.

 

That would make some variation of the trek design more feasible but still unlikely. About the only way it would be more likely would be if it could accelerate for days on end at 1g, which is impossible for modern rocketry.

[Nuke]

you actually can forgo a lot of the engineering in managing the stresses of launch and reentry. you can effectively launch at low velocity possibly using some light atmospheric engines, even just ducted fans or props. you simply shut em down when the atmosphere is too thin and coast out, then fire up your vacuum rated drives.

in space things get weird. removing gravity from the equation your ship no longer responds to gravity as any normal ship would. travel would be direct point to point on a straight trajectory. you could effectively arrive at your destination at a walking pace and re-enter at significantly safer velocities. but if you don't mind pulling a few gs in an aerocapture maneuver you could save some fuel, but requiring some heat shielding. it would probably be better just to use a little more fuel and come to a slow velocity before entry since you really aren't paying for gravity losses anymore and you can build a lighter ship that doesn't have to handle any g loads beyond what its drive can do.

for geometry i think i might actually want to go with a saucer or some kind of toroid, a sphere perhaps. presumably you are taking the gravity away both for the ship and its crew, even on a planet, so you probably want to facilitate a centrifuge.  

[Spacescifi]

10 hours ago, Nuke said:

you actually can forgo a lot of the engineering in managing the stresses of launch and reentry. you can effectively launch at low velocity possibly using some light atmospheric engines, even just ducted fans or props. you simply shut em down when the atmosphere is too thin and coast out, then fire up your vacuum rated drives.

in space things get weird. removing gravity from the equation your ship no longer responds to gravity as any normal ship would. travel would be direct point to point on a straight trajectory. you could effectively arrive at your destination at a walking pace and re-enter at significantly safer velocities. but if you don't mind pulling a few gs in an aerocapture maneuver you could save some fuel, but requiring some heat shielding. it would probably be better just to use a little more fuel and come to a slow velocity before entry since you really aren't paying for gravity losses anymore and you can build a lighter ship that doesn't have to handle any g loads beyond what its drive can do.

for geometry i think i might actually want to go with a saucer or some kind of toroid, a sphere perhaps. presumably you are taking the gravity away both for the ship and its crew, even on a planet, so you probably want to facilitate a centrifuge.  

 

Certainly interesting. I was thinking to use a nuclear light bulb rocket with air intakes and liquid methane for propellant. Should save on fuel, since I will retain most of my aqcuired speed as air is getting thinner the higher the vessel goes.

As for shape, I would go for a thick and blocky folding hexagram.

Basically a cross within an X. Six rocket thrusters near the ends of each rectangular beam under the belly. I would either wait for the air to lift the vessel far enough off the ground or do a quick pulse burn.

Once my vessel has cleared the ground enough, I would make the entire vessel fold downward so that it looks it is like a bundle of thick rectangular beams.

This I would do to reduce drag somewhat during ascent. Main engines would actually be on the end face of every rectanfular beam, so the ship would have to fold and be elongated to actually use it's main engines.

Crew habitat: Since air pressure weakens corners, I would have the crew within an inner inflated habitat.

And that's it. I would expect my rocket flames to be a mix of violet and blue due to the mix of liquid methane and intaked air pumped through the nuclear lightbulb.

In space though, my guess is that the it will just be a short blue flame, as there is no air, just liquid methane propelllant.

 

Edited September 19, 2019 by Spacescifi

[Nuke]

a military ship would definitely want aerocapture and hot launch capability. so an egg shaped ship (think overlord from battletech) might be the best shape for that and your drive might have high enough acceleration for thrust gravity rather than a centrifuge.