Launching ships from the ISS?

[Crewman47]

Not sure if it's been discussed before but are we not at the stage yet where if we want to be able to get a ship and a team of astronauts back to the Moon or out to Mars then can't we use the ISS as a launching platform, obviously when the two points are in alignment, after getting prebuilt ship parts up to the ISS and put together?

It's just that the way I understand it is that the hardest part about getting to the Moon or Mars is the whole getting off the Earth in the first place which uses a lot of fuel just to do so. We could always have fuel at the ISS, a preassembled ship and, if we time it for the shortest distance available, we could get to Mars in whatever time it takes?

 

[Alidar Jarok]

Isn't it easier to assemble a spacecraft in a place with gravity and friction?

 

[Lieut. Arex]

One of the biggest problems with using the ISS as a site for constructing and launching lunar or deep-space craft is its orbital inclination. It's far too high to make the operations efficient. The ships would have to burn a lot of fuel to adjust the plan of their initial orbit to match that of the Moon or Mars. And if the mission is to return to the ISS, the process has to be repeated in reverse. The more fuel you need, the less mass you can carry for instruments. supplies, etc. The originally proposed orbit for the U.S. Space Station Alpha would have been much better, but when the Russians came on as partners, the orbit's inclination raised to make it easier for them to reach the station from their launch site.

 

[sojourner]

^Yep, so the idea of the ISS as a waystation literally became a dead end.

 

[Admiral Buzzkill]

Isn't it easier to assemble a spacecraft in a place with gravity and friction?

Must be, that's why Starfleet built the Enterprise in Riverside.

 

[flux_29]

If we were to buid a ship the size of the enterpris with today's fuel, or like it. how big would the blast radius be - as the shuttle launch it's somthing like 3-5 miles. (were people can safley watch)?

 

[Crazy Eddie]

^ A 300,000 ton space craft using LOX/LH2 would require 2.5 million tons of propellant in order to achieve orbital velocity. It would take the combined force of 19,600 rocket engines (SSME class or better) firing simultaneously in order to achieve liftoff. That means your rocket would be producing the equivalent of a small thermonuclear detonation EVERY SECOND. From overpressure alone, that'd give you a blast radius of around 15 miles or so, though you wouldn't want to be any closer than 25 unless you want to get knocked on your ass when the blast wave hits you.

As for the OP: the point of building ships in orbit is that you don't need a freaking enormous rocket to get all your hardware into orbit, you can do the same job with a bunch of smaller (and therefore much cheaper) rockets and assemble the finished product out of the gravity well. The main advantage of this is you only have to launch that hardware once: a booster, a capsule, a science payload, etc; after the thing is assembled and completes its first mission, you can use it again and again as many times as you want, all you have to do is keep launching propellant to refuel and resupply it for each mission.

Arguably, the ISS itself could be converted into an interplanetary space craft if you docked a big enough engine to it.

 

[flux_29]

^ A 300,000 ton space craft using LOX/LH2 would require 2.5 million tons of propellant in order to achieve orbital velocity. It would take the combined force of 19,600 rocket engines (SSME class or better) firing simultaneously in order to achieve liftoff. That means your rocket would be producing the equivalent of a small thermonuclear detonation EVERY SECOND. From overpressure alone, that'd give you a blast radius of around 15 miles or so, though you wouldn't want to be any closer than 25 unless you want to get knocked on your ass when the blast wave hits you.

But what about space engines that uses nuclear fussion, (i seem to remember protests about Cassini and plutonium) isn't that anymore powerfull?

 

[Lindley]

But what about space engines that uses nuclear fussion, (i seem to remember protests about Cassini and plutonium) isn't that anymore powerfull?

Fission and fusion are means of generating heat energy, which can be converted to electricity in various ways. What we need for propulsion is kinetic energy, and so far we don't really have a better way of doing that than shooting something out the back of a rocket at high speed.

 

[flux_29]

But what about space engines that uses nuclear fussion, (i seem to remember protests about Cassini and plutonium) isn't that anymore powerfull?

Fission and fusion are means of generating heat energy, which can be converted to electricity in various ways. What we need for propulsion is kinetic energy, and so far we don't really have a better way of doing that than shooting something out the back of a rocket at high speed.

Ok, what about combining nuclear fission with ion propulsion?

 

[sojourner]

Ion propulsion is high impulse, low thrust. You can't use it to lift off from earth.

 

[flux_29]

^ ok, but what about the thread? A good horse for launching from the ISS?

 

[Mark_Nguyen]

That point htat should be addressed is WHY you would wnat to use the ISS (or any station) as a platform anyway. Ideally, since all the consumables and other payloads would have to be pre-launched aboard the spacecraft's modules anyway, why even bother to build it next to the ISS? There should be no need for people to physically assemble it in orbit, and should anything go wrong the parts and expertise to fix anything before departure would have to be sent up separately anyway. Why use the ISS as a waystation if you can go straight there?

As marvelous a technological achievement the ISS is (sic), they don't exactly have resources available to do much more than they have already. The parts and skills they have on hand are ONLY what's needed to fix the station itself; it's not like they have reserve bits of stuff that could be used to repair the the shuttle while it's there. The pipe dream of having a space station be around to fix satellites won't work either, since most satellites today are cheaper to replace than to fix.

Aside from the orbital mechanics, it jsut makes sense to have everything ready on the ground, then launch it into orbit and assemble it automatically before a crew even shows up. The original Constellation project had no plans to stopover at ISS, but to go straight to the moon, or to Mars without a lunar layover.

Mark

 

[Crazy Eddie]

^ A 300,000 ton space craft using LOX/LH2 would require 2.5 million tons of propellant in order to achieve orbital velocity. It would take the combined force of 19,600 rocket engines (SSME class or better) firing simultaneously in order to achieve liftoff. That means your rocket would be producing the equivalent of a small thermonuclear detonation EVERY SECOND. From overpressure alone, that'd give you a blast radius of around 15 miles or so, though you wouldn't want to be any closer than 25 unless you want to get knocked on your ass when the blast wave hits you.

But what about space engines that uses nuclear fussion, (i seem to remember protests about Cassini and plutonium) isn't that anymore powerfull?

No.

And even if it was, I'm describing the amount of raw power required to launch something the size of the Enterprise. A more powerful engine doesn't change this, it just means you need fewer OF them.

 

[Crazy Eddie]

That point htat should be addressed is WHY you would wnat to use the ISS (or any station) as a platform anyway. Ideally, since all the consumables and other payloads would have to be pre-launched aboard the spacecraft's modules anyway, why even bother to build it next to the ISS? There should be no need for people to physically assemble it in orbit, and should anything go wrong the parts and expertise to fix anything before departure would have to be sent up separately anyway. Why use the ISS as a waystation if you can go straight there?

As marvelous a technological achievement the ISS is (sic), they don't exactly have resources available to do much more than they have already. The parts and skills they have on hand are ONLY what's needed to fix the station itself; it's not like they have reserve bits of stuff that could be used to repair the the shuttle while it's there. The pipe dream of having a space station be around to fix satellites won't work either, since most satellites today are cheaper to replace than to fix.

Aside from the orbital mechanics, it jsut makes sense to have everything ready on the ground, then launch it into orbit and assemble it automatically before a crew even shows up. The original Constellation project had no plans to stopover at ISS, but to go straight to the moon, or to Mars without a lunar layover.

Mark

IMO, that just supports the logic of converting the ISS to a mobile platform anyway. Give it a drive section and enough propellant (an array of ion engines or even some uprated VASIMRs) and you could send it on a sixty-day expedition to the moon and back without having to develop new exploration architecture. The station is ALREADY designed to support long-term habitation and is already mostly self-sufficient in the short term; anything that can go wrong in the ISS can go wrong on a purpose-built exploration space craft anyway, but the ISS has the advantage of a proven design whose quirks and specs are already well known by its crews.