"Bussard ramjet" for collecting fuels from the atmospheres from suns and planets.

[kspnerd122]

Oh, and starlifting is realistic, although coronal particles are 2 million kelvin, that doesnt mean much considering how low the density is, think of it like sticking your hand in a hot oven without touching anything, to sticking it in a pot of boiling water(at the same temperature) so you can fly into the corona of a star easy enough, the only ISSUE with this is that the radiant energy from the sun at that distance starts to be coming in from the sides a bit more, so your shield will start to need to look like a bowl to keep reflecting the light and particles from your ship, However, red giants are both very cool and very thin(compared to a main sequence star of equal mass) so you could realistically fly right through one and not get incinerated if your shielding was good enough.

 

[darthgently]

On 7/16/2022 at 12:06 AM, Ember12 said:

Refueling from a star?  Just... no.  You can't do it.  The sun's corona clocks in at two million degrees Kelvin.  There is literally no material known that can stand up to even a fraction of that.

Also, unless one's periapsis is already near enough the star to do something like this, the DV required to drop PE that far would be very expensive

[Timmon26]

When it comes to mining gasses from atmospheres (let's assume planetary and not stellar to keep things simple), there are generally two proposed methods.

The first is to drop a refinery into the atmosphere, a big airship basically, held aloft by either lifting gasses or heated air. This refinery would take in atmosphere, crack whatever propellants you need out of it, liquify them, and store them for visiting spaceplanes and rockets. This was the method proposed for fueling Project Daedalus. The main problem with this is that in order to get the mined fuel into orbit, your visiting tanker ships need to accelerate it up to orbital velocity from near zero, fighting gravity and atmospheric drag and all that, presumably in a deep gas giant gravity well. So there are a lot of losses getting the fuel to orbit, naturally, and your tanker ship needs to be fully reusable and capable of reentry, docking with the airship again, blah blah it's a hassle...

The other method is to collect fuel gradually from the rarified upper atmosphere, with some sort of dedicated scoop ship, while near orbital velocity. This has been proposed as early as 1959 in the form of PROFAC (PROpulsive Fluid Accumulation), and ToughSF has a good rundown of the method here.

Spoiler

The scoop ship doesn't have to be especially aerodynamic, it just needs to have lots of frontal area for collecting gas. Basically the main problem with this method is power. Your scooper needs power to cool the incoming (at orbital velocity) air so it can be stored as a liquid, it needs power to perform whatever ISRU chemical conversions are needed, and it needs power to re-accelerate the collected air back up to OVER-orbital velocities with some kind of rocket engine to counteract the drag forces so it doesn't re-enter. This suggests some kind of high-I_sp electric engine is probably needed, like a plasma or MPD thruster. The high power requirements could be met by a nuclear reactor or gobs of solar panels (stretched long and thin along the scoop's main truss so as to not increase drag). The scoop will also need substantial radiators to handle the heat from the engine, reactor, cryocoolers, turbomolecular pumps and such. An alternative source of power could be via remote beaming, from one or several laser satellites or stations in higher orbits.
The overall mass of the scoop ship almost doesn't matter, only the frontal reference area and the available power, as these determine how much drag the ship experiences and how much it can overcome with thrust. 
Somewhere along the scoop's truss will be a number of tanks that will slowly accumulate propellant. When the scoop is full, the engine throttles up to kick the scoop into a higher orbit where it will rendezvous with a depot or waiting ship. The propellant is offloaded, then rinse and repeat. 

With the delivery routes system in KSP 2, player's should be able to model something like this, by launching a scoop ship from a space station and recording a delivery mission with it. If there won't be any aerostat colonies or vehicles in the game (no evidence so far), it'll be the only practical way of mining gas giant atmospheres, which are realistically the best source of He3. 

Edited July 31, 2022 by Timmon26

[kspnerd122]

I mean, you can also just dive in, use some fusion or fission thermal jet and then fly along at airplane speeds sucking up gas

[Ember12]

1 hour ago, kspnerd122 said:

I mean, you can also just dive in, use some fusion or fission thermal jet and then fly along at airplane speeds sucking up gas

But if it's a gas giant like Jool, getting up again will take some serious delta V.

 

[kspnerd122]

A thermal jet uses the atmosphere as fuel, as in, more than half of the required Dv is essentially free(you have effectively infinite fuel in atmosphere) Also, these can often be bimodal(Similar to RAPIER engines, but fusion powered) these engines, in vac, have ISPs that are about 3 times that of the stock nuke, and a loveton more thrust, and your main issue is just get out of the atmosphere, after you get out of it you can just light your hyper efficient engines and get back to orbit for cheap

[kspnerd122]

Did you not hear what I said, as long as your in atmosphere your engines arent burning fuel, so you can accelerate to some 3 km/s without using fuel and then switch to closed cycle but absurdly efficient fusion engines

[Ember12]

16 hours ago, kspnerd122 said:

Did you not hear what I said, as long as your in atmosphere your engines arent burning fuel, so you can accelerate to some 3 km/s without using fuel and then switch to closed cycle but absurdly efficient fusion engines

I did see that message, and I agree that thermal jets would make this much more feasible.

[Minmus Taster]

I know many issues with the ramjet have been pointed out but what about debris protection? hitting a grain of dust traveling that fast will vaporize your craft and you can't put some sort of shield on it because it needs to be open, and there is a point where a particle is too large to be affected by the scoop.

Edited August 7, 2022 by Minmus Taster

[Ember12]

3 hours ago, Minmus Taster said:

I know many issues with the ramjet have pointed out but what about debris protection? hitting a grain of dust traveling that fast is vaporize your craft and you can't put some sort of shield on it because it needs to be open and there is a point where a particle is too large to be affected by the scoop.

Are you talking about harvesting from stars, or gas giants?  Because we already ruled that stars are not doable, and going through a planet, you won't be going any faster than normal.

[Minmus Taster]

7 minutes ago, Ember12 said:

Are you talking about harvesting from stars, or gas giants?  Because we already ruled that stars are not doable, and going through a planet, you won't be going any faster than normal.

I'm talking about gas planets, given the higher gravity and the altitude needed for the amount collected to be profitable your gonna need to go really fast and assuming you figure out the extreme heating and the aerodynamics of the craft a grain of dust at that speed would destroy it or damage it so the forces already at play do the rest.

[Ember12]

20 minutes ago, Minmus Taster said:

I'm talking about gas planets, given the higher gravity and the altitude needed for the amount collected to be profitable your gonna need to go really fast and assuming you figure out the extreme heating and the aerodynamics of the craft a grain of dust at that speed would destroy it or damage it so the forces already at play do the rest.

Agreed, although the real issue with dust will happen during interstellar travel.

[kspnerd122]

um

17 hours ago, Ember12 said:

Are you talking about harvesting from stars, or gas giants?  Because we already ruled that stars are not doable, and going through a planet, you won't be going any faster than normal.

Stars, under known physics, is VERY possible

[Ember12]

1 hour ago, kspnerd122 said:

Stars, under known physics, is VERY possible

Can you please explain the math that supports this conclusion?

[kspnerd122]

Its known as starlifting, essentially, you heat up a tiny bit of the sun to extreme temperature so gas flies off, then you magnetically collect said gas, and its not just Hydrogen and helium, there are also heavier materials, the sun alone has 666 earth masses of iron alone, so if you can pull off starlifting, it provides essentially infinite resources

You collect both solar wind and your own artificial solar wind(by heating up bits of the sun to be hot enough to fly off) by magnetic fields, then just sit, if you could say, use 10% of the suns energy to starlift, you are talking about ~10% of the moon's mass removed/year(or 0.001 Earth masses/year, or 5.9 × 10^21 kg)

Edited August 8, 2022 by kspnerd122

[Ember12]

1 hour ago, kspnerd122 said:

Its known as starlifting, essentially, you heat up a tiny bit of the sun to extreme temperature so gas flies off, then you magnetically collect said gas, and its not just Hydrogen and helium, there are also heavier materials, the sun alone has 666 earth masses of iron alone, so if you can pull off starlifting, it provides essentially infinite resources

You collect both solar wind and your own artificial solar wind(by heating up bits of the sun to be hot enough to fly off) by magnetic fields, then just sit, if you could say, use 10% of the suns energy to starlift, you are talking about ~10% of the moon's mass removed/year(or 0.001 Earth masses/year, or 5.9 × 10^21 kg)

You are right that this is possible.  I think this is much too far in the future for KSP2's scope, but I did misspeak when I said that we had established that it was impossible.  Correct statement: Flying a ship through a star, with technology we might hope to develop in the next few centuries, is very nearly impossible.

[kspnerd122]

Who says you need to fly through a star, starlifting works smaller scale too, not just on the scale of removing lunar masses in the span of a decade

[Ember12]

32 minutes ago, kspnerd122 said:

Who says you need to fly through a star, starlifting works smaller scale too, not just on the scale of removing lunar masses in the span of a decade

Sure, but the process you described would take an incredible amount of energy, enough that you'd be better off just flying to a gas planet.  Plus, the gases in stars are not as good for fusion as the ones found in gas giants.

[kspnerd122]

You mainly mine a star for building material, also, stars much more easily supply the energy for their own dissasembly

[kspnerd122]

Again, who said you are doing fusion, you could, again, mine hundreds of tons of metals to use for construction, or you could do another use of stars for propulsion other than solar sails

Stellasers, essentialy, you go set one up and now u have a giant laser beam to push stuff with

[Ember12]

3 hours ago, kspnerd122 said:

Again, who said you are doing fusion, you could, again, mine hundreds of tons of metals to use for construction, or you could do another use of stars for propulsion other than solar sails

You could, but this would require a lot of very futuristic tech also.  I don't doubt that this stuff can be done, but I don't think it can be done within KSP2's technological scope, or if it can, it would not be as practical as conventional mining.

Edited August 10, 2022 by Ember12