KASASpace

Everything in KSP is scaled down, but when I looked at Jool's radius, I noticed it was around 6,000 kilometers. That's ten times Kerbin, which if I recall is supposed to be one-tenth the size of Earth. So, Jool is small. Now, on to my question, could a gas-planet the size of Jool even form in a young solar system?

If you want to get to a reasonable fraction of the speed of light, like 70%, then you need a mass fraction that is just GINORMOUS, even with antimatter. So, probably not getting to .7c anytime soon, but if fusion is on its way like people say, we might get .1 or .2c. Orion could get to Alpha Centuari in ~130 years, if we build the interstellar version that's fast. Basically, it's possible, but the biggest obstacle is not mass fractions or speed, but POLITICS. Who's going to fund a .1c probe?

I said OTRAG's staging, not OTRAG itself. If a model rocket is a low power motor and a small-ish size, you can!

Actually gas-giants may not have hydrogen, but a lot of them do. However, that close to Jupiter the radiation is probably too extreme for almost any civilization's technology to survive.

We actually know very little about the outer planets of those systems, because they might be taking too long to pass in front of the star for direct observation, or the "wobble" is so small due to distance that it's not observable.

I chose propane because it's more efficient, almost 30 to 50 increased Isp over kerosene, and it's a lot easier to acquire propane. I don't know, perhaps some sort of magnetic acceleration? A hydraulic system akin to the systems onboard carriers? I never said it was final. There are other methods.

Too much weight? Do you understand how a ramjet works? It's practically a tube with an injector, although that's a gross exaggeration. A ramjet's biggest difference from a scramjet is geometry, so not much increase of weight there. The heaviest engine will most likely be the rocket engine itself, although it could be pressure-fed, but that's not that efficient. I never said that, I said: A turbo-compressor is complicated, and that's why I didn't mention having one onboard.

Actually, 10x10x5 cm kits are available, and if we do a PR mission first I would say that is the size to go with.

Perhaps, if we only get LEO, we could launch a 1U that can separate. It then flies away a bit, rendezvous with the detatched piece and dock. We could use this to test out in-space refueling, with multiple consumables transferred (electric charge, fuel for propulsion, etc.)

Yes they are, but you will gain large amounts of cross-range capability with engines. Plus, ramjets are extremely simple, with virtually no moving parts.

What about landing on Europa? Perhaps with airbags? It hasn't really been done has it? Maybe Enceladus? I say this because it's bold and very KSP. Problem with this is mainly radiation, but I don't know about Delta-v requirements to Europa. I would go with a 2U because it seems like a better plan than a 1U, 2Us have up to four times the volume, unless it's just two 1Us attached at one side.

A custom built model rocket could all right. Most model rockets with store-bought engines have fuel only in the engine, giving really small Delta-v. Now, using extended fuel tanks you could do it with a simple guidance system and "infinite" staging, which means staging immediately around a core (OTRAG did that).

We wouldn't survive that impact. But maybe smaller. There's still the possibility of maintaining an underground forest and get charcoal from it.

You forget, that it is not the metals that matter, but something much much different. Even if we were blasted into the Neolithic age, I know about a piece of technology that could take us to the Bronze Age, it's called the Bellows. It's a compressible container that "blows" air into a fire, making it hotter. This allows for that fire to melt metals. Then we can use those metals to make tools. Plus, that would only happen if everyone with knowledge about industrial technology died in that disaster.

That's a good point. Although it would depend on a lot of factors, like where Jupiter is in the solar system (if you can get an encounter where the gravity of Jupiter can pull you towards the sun's retro grade vector, then it's possible.)