Calling all space enthusiasts

[Broomstick]

Avoiding using the SSME for very good reasons left them with very little fuel, did it not? If you can't use an engine and fuel for fear it will blow up then it might as well not exist. A direct abort is "better" only if it's not likely to kill you when you attempt it.

Not that I want to argue details here, the point is a lot of folks in the street at the time could not under stand why looping around the Moon was better than simply reversing course. The idea of using a large body's gravity to first pull you one way then alter course to go another just didn't make sense because here on the surface of a planet we don't travel in that manner.

[someone_else]

Mandatory Atomic Rockets link about boosters and general education about space movement.

EML-1: the next logical destination an article talking of the issue discussed here too.

That said, I'm pretty sure you would be far better off making a Moon mining base and a Moon elevator (feasible with current tech) to take the bulk of the raw construction materials and space tug fuel (especially space tug fuel) from the moon's surface.

To the bare minimum you're mining water ice, which can then be cracked to become oxygen and hydrogen, and then either stored as fuel or breathed in the life support.

Chemical rockets suck as surface-to-LEO ferries. Space shuttle manages to suck even more.
You need to reach ludicrous speeds even to go to the moon, nevermind going to lagrange points.

If we had a station at Earth-Moon L1, would we even need propellant to get stuff from the station to the moon/Earth? would we just give it a nudge, perhaps with a launcher on the station, and let gravity do the rest?

Hell yes.
The point is that you have an "orbital speed", which is the speed that keeps you from falling down.
To change orbit you need to reduce the orbital speed (and your orbit's radius decreases) or increase (and orbit's radius increases)

A quick premise: in space what counts is both speed and fuel efficiency. Acceleration is largely irrelevant (unless it is a passenger transport).
It doesn't matter if you can accelerate at 1000 gees for a few hours if you haven't reached the right speed when your tanks are dry. (then you'll probably slingshot in deep space, and die horribly)

Just to go from LEO to lunar orbit (and L1 is somewhere towards the sun at 3.75 times that distance), you need 4.1 km/s of deltavee (increase of speed) which is pretty close to the max theoretical deltavee available with chemical rockets without staging (i.e. making an irrecoverable disintegrating totem pole like Saturn).

Now, you can use a solar or an electrostatic sail and that saves lots of fuel, but it will be a sloooow voyage.
A slightly fastest way is using electric engines, that use energy from solar panels to boot off noble gas ions out of the nozzle.
Using NERVAs (nuclear rockets heating and expelling hydrogen through the nozzles) would be a good choice for such "ferry" task, if they don't get all scared down on Earth.

And I'd heard of the Interplanetary Transport Network, it's a fascinating idea, and a brilliant one.

It is also a very slow one. That's two years to go out to lunar orbit. Unsuitable for anything else than cargo barges.

[Skgoa]

Mandatory Atomic Rockets link about boosters and general education about space movement.

You forgot to add " in pulp scifi". Atomic Rockets is full of misinformation and not really thought through wankfests.

[PeZook]

Avoiding using the SSME for very good reasons left them with very little fuel, did it not? If you can't use an engine and fuel for fear it will blow up then it might as well not exist. A direct abort is "better" only if it's not likely to kill you when you attempt it.

Yes, that's true. I suppose the problem is the instinctual disconnect between "Taking the longer route" and the reason "Because it will conserve fuel", as all travel on Earth works entirely differently: it is always better to take a shorter route if you want to conserve fuel, barring very specific circumstances like airplane flyovers of the Atlantic where you can use high-altitude winds. And even then you won't save any fuel by taking a route 3x as long

I was just commenting on the fact that you said going around the Moon was faster for Apollo 13 than a direct abort would've been, which isn't true: if they could do a direct abort without fearing another explosion, they could've avoided all the problems with oxygen and power supplies that plagued them later.

Not that I want to argue details here, the point is a lot of folks in the street at the time could not under stand why looping around the Moon was better than simply reversing course. The idea of using a large body's gravity to first pull you one way then alter course to go another just didn't make sense because here on the surface of a planet we don't travel in that manner.

I find it easier to explain these concepts to people if I describe space travel not as travel per se, but as throwing really large things between planets. It appeals more to our usual instinct, I guess, since spacecraft do behave like objects thrown without an atmosphere.

[someone_else]

You forgot to add " in pulp scifi". Atomic Rockets is full of misinformation and not really thought through wankfests.

You sure you didn't just look at the images? Unless you want to call Heinlein or Clarke or 2001 space odissey "pulp sci-fi".
The math is useful, and most info about space is valuable for a layperson albeit maybe too obvious for a guy like you.
Of course there are also various people's opinions on handwaving stuff that looks reasonable. (like the sections about guns and spacecraft combat, or about empires or future history)
But those are more a resource for writers than anything else.

Anyway, what about something better? I'm always open to improvements.

[Sarevok]

Atomic Rocket's author posts here as well under the name Nyrath. He is indeed knowledgeable about the speculative matter of space combat. I would buy his conjectures over others simply because of the level of detail he has gone into analyzing the subject.

Anyway Atomic Rocket does not purport to present the "ONE TRUE WAY" to fight in space. He presents various options with their relative realism, advantages and disadvantages compared and contrasted. It is upto the reader to pick which is most suitable for their own vision of how space combat should be.

[Skgoa]

Its a great site, I have enjoyed reading it many times. The main beef I have with it is that its not sufficiently distinguishing between real world concepts and ridiculous things scifi authors (or sometimes stage building departments) have come up with. I guess it can be a great ressource for people who don't care that much about reality, but just want (to write) realistic/plausible science fiction.
Basicaly what I am trying to say comes down to "take it with a grain of salt".
e/ Also, the author should do something about the way he uses numbers and equations. Its just needlessly cluttered and often there is not much text explaining whats going on. And of course the page on detection has math on it that debunks the claims made in the text.


A good place to start getting real world rocket science would be my Professor's textbook. No really, its a great and relatively simple introduction to all important concepts. Unfortunately its in german.
I guess there should be english language textbooks available, I can also recommend wikipedia, although more for an overview and for the links at the bottom of the pages. And I have been thinking about mentioning http://www.nasaspaceflight.com/ - it's forum has many generally knowledgable people and much information, unfortunately there are quite a few nerd scfi wankers there, too. But as long as you don't believe everything they write (it can get pretty ridiculous, but so can sd.net) you should be fine.

Oh and there is something else I want to mention for the other german speaking users: http://www.raumzeit-podcast.de/ is an excellent podcast by the DLR/ESA.