[castor]

Yeah, it'd only need fuel to "stop" the "movement".

[S-99]

A midway station to be in between the journey to mars would be a great idea. It'd just be an area strictly for resupply that's regularly strocked.

[Androgeos Exeunt]

By the nature of its flight path.  As the article mentions, the two Voyager probes were designed to take advantage of gravity assist, the "slingshot effect" that occurs when a smaller body interacts with a much larger body and gains momentum.  Because of the unique alignment of the outer planets at the time of the launches, both Voyager probes had the option of slingshotting by all four of them (though only Voyager 2 exercised that option; Voyager 1 was diverted to pass by Titan, which altered its trajectory).  Both Voyagers achieved escape velocity from the Sun, meaning that they're no longer gravitationally bound to orbit it.  Neither craft has any boost thrusters of any sort; all of their velocity was gained from their initial launches and subsequent gravity assists.

Ah yes, of course. What's it called on Wikipedia, "drafting". It's something that applies to Daytona USA.

I also forgot that there's not much friction in a vacuum, if not none.

A midway station to be in between the journey to mars would be a great idea. It'd just be an area strictly for resupply that's regularly stocked.

I think so too. It is good to note, though, that space stations need to be sent up in stages. Both Mir and the ISS were and are space stations made up from much smaller modules.

Has any human even reached the midpoint between Earth and Mars in the first place?

[Mongoose]

Has any human even reached the midpoint between Earth and Mars in the first place?

No human's ever been further from the Earth than in orbit around the Moon, which was obviously accomplished during one of the Apollo missions.

[DeepSpace9er]

Perhaps the ISS should have been at one of the Lagrange points instead of a mere 300km up. What I find REALLY silly is they are still building the thing when its slated to come crashing down in 5 years or so.

[fener]

Well as long as the ISS has the means to change altitude via it's own thrusters or those of a docked vehicle, I don't think it'll be coming down anytime soon.

http://www.heavens-above.com/issheight.aspx

As for bases at Lagrange points, still need a cost effective way to get stuff there and return before we can think of building anything.

So either we need a breakthrough in the field of electric propulsion, or someone builds a space elevator.

[General Battuta]

Perhaps the ISS should have been at one of the Lagrange points instead of a mere 300km up. What I find REALLY silly is they are still building the thing when its slated to come crashing down in 5 years or so.

Um, no it's not.

However, it might very well fall apart and be abandoned. Of course, that article's from 2004, and we've managed to keep it going since then, but I doubt it's much improved.

[perihelion]

Electric propulsion is of little use until you are already in orbit.  Specific impulse for even the more exotic electric drives are still orders of magnitude too low to get anything off the ground.  I'd love to see them developed, but the big problem is surface-to-orbit.  The ability to move from low orbit to higher orbit is important, but secondary.

A space elevator, as crazy as it may sound, is probably the most practical solution.  Manufacturing techniques are still a good ways off from being able to make cable strong and durable enough to do it.  Maybe in the next couple decades, though.  The other thing you need is a counter-weight.  The most sane way of getting enough mass into orbit to act as an effective counterweight is to capture a small asteroid and move it there, but it doesn't take much imagination to see what kind of public panic that idea would cause.

[DeepSpace9er]

Perhaps the ISS should have been at one of the Lagrange points instead of a mere 300km up. What I find REALLY silly is they are still building the thing when its slated to come crashing down in 5 years or so.

Um, no it's not.

However, it might very well fall apart and be abandoned. Of course, that article's from 2004, and we've managed to keep it going since then, but I doubt it's much improved.

The projected completion date is 2010, with the station remaining in operation at least until 2016.

from http://en.wikipedia.org/wiki/ISS

So the point is, it spends most of its life being built, then 6 years after its slated to be finished its going to be intentionally burned up.

[General Battuta]

I doubt it'll be finished by 2011, but I also doubt it'll be shut down by 2016. Mir, for example, lasted well beyond its projected expiration date.

[Mars]

Electric propulsion is of little use until you are already in orbit.  Specific impulse for even the more exotic electric drives are still orders of magnitude too low to get anything off the ground.  I'd love to see them developed, but the big problem is surface-to-orbit.  The ability to move from low orbit to higher orbit is important, but secondary.

A railgun like device has been proposed for launching objects into orbit. Also the main thing limiting electric propulsion is the amount of electrical energy available. A sufficiently large power source would increase both specific impulse and thrust, although the increase becomes exponentially smaller per watt. I don't know if it's possible to have a large and light enough power source to allow a spacecraft using electric propulsion to make it off the ground, let alone into orbit, but it's certainly possible for them to be more powerful than they are now.

[Androgeos Exeunt]

As I understand it, is a railgun considered to be a mass driver?

[Mars]

Well yes, but instead of a spacecraft projecting the mass backward to attain thrust, the spacecraft IS the mass, the (very large) railgun accelerates the spacecraft on the ground and essentially shoots it into orbit. I forgot what the idea was called.

[perihelion]

Yes, a rail gun is essentially a mass driver.  And for certain raw materials or particularly hardy pre-fab equipment, it might even work.  What it will never do is get human beings off the ground.  Even if the magnetic fields involved weren't strong enough to rip the iron out of your haemoglobin, the acceleration involved would almost certainly kill you.

I do like the idea for shooting heavy equipment into orbit, though.

As for a problem with electric drive being making large enough quantities of electrical power... I'll grant that it is a contributing factor, but mostly it is a question of design intent.  Take the ion drive, for example.  You are essentially taking a rarefied noble gas, ionizing it, and accelerating the ions using a high voltage electric field.  Ok.  You can do this with pretty high efficiency.  However, you don't really get much push from the drive because you aren't discharging much mass at all.  Yes, what mass leaves the ion drive is moving pretty fast, but momentum = mass * velocity.  To overcome the fact that mass is low for this type of drive, you'd have to accelerate your ions monstrously hard.  That means even higher voltages.  There are practical limitations to how high a voltage you can reach before you start having serious problems.

A plasma drive might scale a bit better with a larger power source.  But it still wouldn't do any good except once you were already in orbit, or at least well past the ionosphere.  With only a few exceptions (most of anchor the launch mechanism to the earth), these electric propulsion systems will only work in a vacuum.

[Androgeos Exeunt]

Perihelion...

In contrast to a space gun, a mass driver can have a length of hundreds of kilometers and therefore achieve acceleration without too high g forces to the passengers. It can be constructed as a very long and mainly horizontally aligned launch track for spacelaunch, targeted upwards at the end, partly by bending of the track upwards and partly by Earth's curvature in the other direction.

It starts at 0 km/h, then accelerates slowly along the track before reaching super high speeds at the other end. The ride should theoretically be as comfortable as when you're in a Bugatti Veyron moving at 407 km/h.

Banking on this idea, perhaps a mass driver could be built on the slope of Mount Everest...

[Mars]

Let's see what ice can do when you're moving at 7 miles a second.

[Androgeos Exeunt]

Let's see what ice can do when you're moving at 7 miles a second.

What's on your mind? I was thinking of either:

- The ice block becomes an armour-piercing shell; or
- Nothing. It melts in a millisecond.

[Mars]

I'm not sure, I was thinking of a massive spacecraft spinning out of control and extremely high speeds and vaporizing in the atmosphere.

In any case I think Everest is out of the picture

[Androgeos Exeunt]

In any case I think Everest is out of the picture

Really? Why?

[Mars]

Let's see what ice can do when you're moving at 7 miles a second.