Bill Phil

Depends on the sci-fi universe. Are we talking War of the Worlds Martian tech, or human tech? There is at least one I know of: Worldwar. It's a series about World War II, and aliens invading Earth while it's embroiled in conflict. Just about the only thing we don't have from that sci-fi universe are the starships.

The Worldwar series by Turtledove is also a deconstruction, somewhat, of the alien invasion story. It's set during WWII, and then the aliens arrive...

Oh, carp. Mine is just a depiction of a depiction of a sword... I'll just say that the sword shows up. That's good. It's one of the better weapons during a zombie apocalypse (although spears are better, atlatls as well...). I guess I also get thunderbolts... And if it's not going to be the sword, I get an entire Space Wing to myself. Hopefully they have some kind of defensive weapons...

Eclipse by Pink Floyd

Saw a total eclipse. And everything under the Sun is in tune But the Sun is eclipsed by the Moon! - "Eclipse", by Pink Floyd

Ah, yes, the ecliptic plane! https://en.m.wikipedia.org/wiki/Ecliptic Oh, wait a minute...

I saw totality, but I wasn't equipped to actually snap a picture of it. I almost had one, but I lost it just before I snapped the photo. Took lots of partial eclipse pics, though.

Higher specific impulse, no matter what body you're launching from, leads to higher payload fractions and lower mass ratios. In the context of SSTO vehicles, launching from Earth, we need higher isp values. We're not discussing Mars SSTO, or Lunar SSTO, or any other solar system body, not at this moment. Discussion on those isn't really what we're talking about here. We can't get to them until we leave Earth. One problem at a time. ITS is, at best, decades away. At worst, the cause of hundreds, or even thousands, of preventable deaths.

And Kerbin doesn't exist. I'm not saying that what Kerbiloid said is false, but it's not very applicable until we have the need to launch from other celestial bodies, which hasn't been done very often. And besides, on Kerbin, 1000s of isp would still be extremely useful and would improve payload fractions enormously.

You could try to get the number for the address, if it has one. Snail mail might also get their attention. Also, Copenhagen Suborbitals are in Denmark. What you mention says it's for Sweden and Finland. Can you even go to Denmark for this?

Interesting idea. I'd like to remake Star Trek II (Into Darkness was not a remake). Mainly because I want Khan to actually threaten the Enterprise and its crew, and maybe even move the destruction of the ship to this movie. Don't get me wrong, I love Wrath of Khan, there's just not much actual wrath.

Well, sure, on different planets you don't need as much Delta-v, but everyone lives on Earth at the moment.

I'm thinking about heading up to a place where the eclipse is total, and then play Eclipse by Pink Floyd while totality is underway.

Most higher isp systems have heavier engines, making multi stage designs a bad idea... Let's do some simple math: Using the rocket equation, 1000 s of isp (9800 m/s) as our exhaust velocity, and 10k as our total delta-v, our mass ratio is barely much higher than e. Less than 3. Less than the A4/V-2 mass ratio. Of course, you need an engine with just as much isp on the ground, or averaging 1000s during the ascent. But with a mass ratio of e, and current high propellant mass fraction tank designs, even with a heavy engine setup we could get significant payload mass fractions. For a 500 Tonne rocket, empty mass would be about 180 tonnes. About 36 tonnes of that would likely be tankage (and that might be a stretch, considering that shuttle ETs were about 27 tonnes empty at their lightest). That gives us about 144 tonnes for engines, structure, and payload, guidance, and so on. 50 tonnes of payload shouldn't be impossible, seeing as an Atlas V can get more than 10 with inefficient chemical engines and something around 300 to 400 tonnes of rocket. Halving exhaust velocity squares the required mass ratio for a given Delta-v. Doubling the exhaust velocity reduces the required mass ratio to its square root. This is why just doubling chemical rocket's current isp would benefit rockets enormously.

You haven't heard of Kansas? That really is the land of corn... and wind turbines.

It depends on exhaust velocity. If your exhaust velocity is low (chemical engines), you need high mass ratios for your rocket. Only way to get around that is staging, without magic materials science. But if your exhaust velocity is high? In the 600 to 1000 second range (~6000 to ~10k m/s), then your mass ratios are smaller. This then increases payload mass fraction. More payload per launch, similar launch costs, (if you're lucky) cheaper access to space. A single stage is simpler, in theory. In practice, it doesn't work well with low exhaust velocities. As they say, the best system is the one that's not there. No interstage, no staging system, one set of engines for the propulsion system, and so on. But it only really works with higher exhaust velocities.

I recommend Stranger in a Strange Land, although it isn't exactly for kids. It was authored by Robert Heinlein. It's really interesting to see his vision of the future compared to the actual future, at least in a few ways.

I talk to guys who work on the SLS. It's pretty hectic sometimes.

The only reason this one is special is its path. There'll be another eclipse in North America in 2024. Not through just the US, though. Canada and Mexico. Eclipses are common. What makes them special is where the umbra falls.

Most of the atmosphere is just a few kilometers above your head. It's not hard to get above it. The gravity turn optimizes the ascent, going up initially for a small amount of time and then turning over, gaining both horizontal and vertical speed, and eventually almost all of the gains are horizontal. Having to add that vertical portion increases Delta-v by large amounts, as well as having to burn engines for long periods.

I don't know what Chang Diaz did to you, but VASIMR isn't just hype. Sure, it's been heavily hyped, and Mars in 39 days is most definitely only hype, however, it's capability as a tug engine isn't nearly as bad as you'd think. You do need lots of power, of course, but that's nothing that can't be handled, and it's by no means unrealistic. No one is saying that the VASIMR engines we have now are going to be working miracles soon. The design has to be developed. Problems need to be addressed. But it's no more or less practical than other near future engines. Certainly more practical than most fusion proposals. Realistically, it may lead to a dead end, but we don't know for sure. That's why it has to be developed. Researched. Judging a system so soon never really helped anything get done. And when it comes down to it, if VASIMR ends up helping the cause, then that's great. If it doesn't lead anywhere, then that's a shame, but then we would actually know whether or not it's useful. Right now it's mostly speculation. What's your reasoning, anyways? Claims generally need evidence. I'm skeptical, but optimistic. My reasoning is that it could be helpful, but a number of people need to actually invest substantially to get good results. Not much is being thrown at it. But there's no reason to throw it out the window. They've managed to run some test firings, so it is being developed. Also, I don't recall solar panels or nuclear reactors being pixie dust...

Depends on how you define powerful. If you mean thrust power, you're right. Even relatively basic chemical engines can get into the Gigawatt range. You'd have to get a lot more thrust power, exhaust velocity and thrust, to do cooler things. That means you'll need beefy reactors and radiators. But before that gets developed, it could be used as a space tug for unmanned payloads to various points in cis-lunar space. It's perfectly fine to take weeks to get out there. OP: There are quite a lot of far-future technologies in that proposal. But even so, space battleships don't make much sense. Essentially you could just use huge spaceships as slugs to obliterate the enemy. Put up a defense network in various orbits around your planet and such, and such a war might not be quite a MAD scenario. Confrontations between ships aren't likely, as adding weapons will hurt your mass ratio and spaceships are very easy to destroy.

Last edit was 2 months ago? Dude, there are wikis who were last edited years ago. Unless you mean years?

Direct landing isn't usually practical. Remember, if you have to double your Delta-v, you have to square your mass ratio. The actual design isn't that important, so long as nuclear electric/fusion rockets have huge radiators and other realistic components, you'll be alright.

Well I guess the actual location could be changed. If it's an annual event, we could rotate the city location.