sevenperforce

I think the question was more "could there be caves preserving ancient atmospheric conditions" rather than "could we use existing caves". But yeah, unfortunately any ancient caverns would have long since equalized by now.

Specifically, if you're crossing from one SOI into another (for example, let's say you were trying to do a Hohman transfer from Kerbin into a higher orbit) then you could do it in two ways. The inefficient way is to burn just outside of Kerbin's SOI, then circularize at Kerbin's orbital distance (but outside of Kerbin's SOI). Then you'd want to do your Hohman and you'd calculate as above, and you'd get a dV of 9,218 m/s. Yikes! The better way to do it is to use the Oberth effect to your advantage. By burning to escape (in the right direction) out of low Kerbin orbit, you can add a lot of hyperbolic excess velocity (basically, the speed-at-which-you-leave-Kerbin) for a small additional burn. Not going to lay out all the maths right here, but by way of example, suppose you want to go from Earth to Mars. It will cost you 3.22 km/s to escape Earth, at which point you would have to do another 3 km/s burn to get from Earth's orbit out to brush the orbit of Mars. However, if you combine the escape burn with a little extra hyperbolic velocity in LEO, then you only need a combined 3.82 km/s to get on your Mars-brushing orbit. That extra 0.6 km/s in LEO becomes an extra 3 km/s in interplanetary space.

If you were in a 13,381,911 km orbit around Kerbin and you were trying to transfer to a 20,000,000 km orbit, then yes, you'd need a 16 m/s burn to start the Hohmann. Assuming that the rest of your math is correct. But you're talking about the sun. The sun's gravity is much stronger and so the numbers are totally different. If you're crossing from one SOI into another SOI, then all bets are off.

@Barzon KermanHere's the full-res completed European rocket chart. They are organized in order of the first launch within a given family by a European launch provider.

On the other hand, if I sort each family of rockets by the earliest launch, then it gets to a much more historically informative approach.

Right, I could line them up based on what they are able to place in a specified orbit. Given that payload capability may not always be easy to find for the older LVs (and could potentially lead to broadly dissimilar rockets being sorted together), it's probably easiest if I sort each family of rockets by the most recent launch from within that family, and sort each family by payload capability.

Okay @NSEP @Mad Rocket Scientist @Barzon Kerman @A Soviet Tank Here's Diamant, Black Arrow, Vega, and Ariane 1-5. Will add labels and put up the full-size version tomorrow...maybe with the cargo Soyuz operated by Arianespace as well. Want me to include the two planned variants of Ariane 6? I have mixed operating + retired and operating + planned but not retired + operating + planned. Also, what order is preferred? I can order them all by height (easy), or order them by date of first launch (interesting) or order them by date of last launch (also interesting) or order them by payload (informative).

Ariane 1-4 (not full size; that will come later):

Yes, I understand that is the system construction you are proposing. If you want to set it up that way, then do the maths and see if it comes out.

No. You can't stipulate away conservation of angular momentum. You are the one who said, "If the person decided to pull themselves closer to the center, that would take energy. At the same time, they would lose kinetic energy (since the rod does not speed up)." That is false. Kinetic energy is not lost; it is compensated for by a minute change in the angular velocity of the entire system. You cannot use the change in rotational kinetic energy of a small mass to set up your physics while handwaving the change in angular velocity of the system. Is the difference minute? Yes. But if you are pretending it doesn't exist, you are setting up your body diagram incorrectly and will get a fallacious result. This is not me being a physics pedant (though I'd gladly accept such blame when deserved); this is me stopping you from creating an incorrect construct of a physical system. If you make the wrong assumptions, you won't get a good outcome.

Here's Black Arrow, the Diamants, and Vega. Ariane families next. I'll have them all in a single poster form; this is just a WIP. I know they're small, but if I don't make the small ones small, the big ones end up with so much detail that it's pretty much impossible. Scale is roughly twice that of historicspacecraft.com.

If a person is hanging on to the end of a rod rotating at constant angular velocity, then pulls herself in toward the center of the rod, then the rod will no longer be rotating at constant angular velocity. Angular momentum must be conserved. Change the moment of inertia, and unless you have a way to change angular momentum, the angular velocity WILL change. The fact that the mass of the rod is much greater than the mass of the person means this angular velocity change will be very slight, but it will nonetheless be there. If you take a scoop of dirt from the equator and carry it to the North Pole, you increase the rotation rate of the Earth.

Of course. That was the joke.

Just bring carbon black. It's dense.

Incorrect. As they pull themselves closer to the center, they will decrease the rod's moment of inertia, and conservation of angular momentum will cause the rod's RPM to increase. Same reason a neutron star can spin hundreds of times per second -- the parent star's modest rotation rate went through the roof when most of its mass collapsed down to a tiny radius.

And it will crack your tank over time as randomly migrating monatomic hydrogen atoms happen to meet up inside the metal lattice and mate. YOU'VE GOT IT Actually, let's bring kerosene and crack that into methane.

Yep. I get 191 kJ for the gravitational potential energy of a 1 kg mass dropped from a height of 20 km, and 108 kJ for the kinetic energy of an object at the equator traveling at the speed of the Earth's rotation. So it's approximately half, but not exactly half.

If the Earth were non-rotating, it would take an overall spherical shape, and its gravitational equipotential would share this shape, although there would be mass concentrations corresponding to the continental plates and local deviations. Since the Earth is rotating, there is a small centrifugal (not centripetal) force working against gravity at the equator. This causes the Earth to bulge at the equator. Because the Earth bulges at the equator, it is lifted farther away from the iron core, and thus experiences slightly less gravitational force. Which makes it bulge more. Which means less gravity, and so forth. So there's no simple equation.

They take me about 1-2 hours of dedicated work, usually spread out over a few days. But if someone just wants to leave $5 as a "thanks" I am not going to be offended.

Heat rejection becomes problematic when you're trying to cool something as cool as liquid hydrogen. The mass of your radiators rapidly outpaces any propellant stock boil-off savings.

Sounds like two different projects, but sure!

Here you go! @Barzon Kerman @A Soviet Tank https://www.gofundme.com/buy-a-guy-a-beer

Open-ended. Whatever someone wants to contribute. I'll start a GoFundMe today or tomorrow. "Rockets for beer money" or some such.

Their new COPVs are supposed to be the safest ones ever designed.

Cold gas RCS on F9 pushes about 50 m/s.