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Another problem not mentioned in the article is that it would be a fixed inclination launch system. Changing inclination costs a lot, especially in low orbits.

Another problem not mentioned in the article is that it would be a fixed inclination launch system. Changing inclination costs a lot, especially in low orbits. For example, from a pure dV standpoint, a GEO satellite would be cheaper to launch from Baikonur by circumnavigating the Moon, than by changing the inclination during the flight as it's currently practiced due to different constraints (the tricky thermodynamics of compact upper stages being the big one).

larkeith 8y ago
I wonder if, once both technologies are more advanced, a network of solar sail "tugboat" drones could be used to transfer launches to other inclinations and orbits after orbital insertion - with the exception of normal wear and tear, there should be little to prevent such a network from operating indefinitely with negligible material cost once launched.
- rtkwe 8y ago
  The biggest issue is that'd take a really really long time. The amount of dV you get out of a solar sail is minuscule at scales that will work well in the neighborhood of Earth.
  - larkeith 8y ago
    Oh, absolutely - solar sails in general only really work for things like satellites and probes (and, possibly, asteroids) where you can afford to give them quite a while to get into place, so no manned solar boats here. Although you can do some interesting things with them in gravity wells (statites, anyone?). Still, you only need to perturb your orbital plane a very tiny bit to be out of the way of future launches, and then you have all the time in the world to navigate to where you want to go.
    - rtkwe 8y ago
      Yeah the months to years it would take depending on the payload and size of the change though would be pretty costly for the businesses. I think a more likely solution would be having a handful of launch loops on common inclinations and anyone requiring a very specific inclination launching with a booster attached to take care of it. Depending on how high these loops could launch using the Moon to change inclinations might work. I think more likely though is that basically everyone would find ways to make do with the handful of standard inclinations that there were launch loops for.
rtkwe 8y ago
That's probably not a huge deal ultimately. Being able to get things into orbits very cheaply will make the dV cost of inclination changes much easier to bear because you don't have to haul all that fuel to orbit on your initial launch any more. Also how many different inclinations are actually required to serve 90-95% of all launches? There's really only a handful of inclination 'classes' out there that would need to be fulfilled; 0 for geostationary, 51.6 for ISS (assuming it's still up when we build the loop), 80-90 for various Earth observation and communication satellites. If we can super cheaply launch satellites into a couple defined inclinations most customers would probably be able to make do with one of these common inclinations rather than today where they'd go with the perfect one.
blauditore 8y ago
If hauling mass into orbit relatively cheaply would be possible, wouldn't it be easy to just send along a counter-mass (or actually a second useful item) and split them when in orbit (e.g. with some explosives)? So you would end up with two symmetrically orbiting items, but without having to deal with rocket propellants.
- ithkuil 8y ago
  so basically a "rocket" (two rockets?) with a high reaction mass?
- CompelTechnic 8y ago
  Low earth orbit is at a speed of 28,080 km/h. If you want to separate the two halves of your satelite at a significant angle from their starting trajectory, you have to provide a lot of impulse perpendicular to the direction of travel (or from a zero-orbital speed vertical launch at apogee, which would be weird). More impulse than an explosion could make, probably even if you built your satellite like a brick shithouse. Rockets conveniently spread the impulse out over a long period of time.
paulmd 8y ago
Changing inclination costs a lot because dV costs a lot. If you can easily bring hundreds of tons of fuel to orbit, that's no longer the case. The launch loop changes everything, because your launch costs are in the neighborhood of $3 per kg. That's a total shift in the way we think about rocketry. Imagine if gasoline was $4000 a gallon. In that world, driving 20 miles to the store to pick up some groceries would be unthinkable.

larkeith 8y ago

I wonder if, once both technologies are more advanced, a network of solar sail "tugboat" drones could be used to transfer launches to other inclinations and orbits after orbital insertion - with the exception of normal wear and tear, there should be little to prevent such a network from operating indefinitely with negligible material cost once launched.

rtkwe 8y ago
The biggest issue is that'd take a really really long time. The amount of dV you get out of a solar sail is minuscule at scales that will work well in the neighborhood of Earth.
- larkeith 8y ago
  Oh, absolutely - solar sails in general only really work for things like satellites and probes (and, possibly, asteroids) where you can afford to give them quite a while to get into place, so no manned solar boats here. Although you can do some interesting things with them in gravity wells (statites, anyone?). Still, you only need to perturb your orbital plane a very tiny bit to be out of the way of future launches, and then you have all the time in the world to navigate to where you want to go.
  - rtkwe 8y ago
    Yeah the months to years it would take depending on the payload and size of the change though would be pretty costly for the businesses. I think a more likely solution would be having a handful of launch loops on common inclinations and anyone requiring a very specific inclination launching with a booster attached to take care of it. Depending on how high these loops could launch using the Moon to change inclinations might work. I think more likely though is that basically everyone would find ways to make do with the handful of standard inclinations that there were launch loops for.

rtkwe 8y ago

That's probably not a huge deal ultimately. Being able to get things into orbits very cheaply will make the dV cost of inclination changes much easier to bear because you don't have to haul all that fuel to orbit on your initial launch any more. Also how many different inclinations are actually required to serve 90-95% of all launches? There's really only a handful of inclination 'classes' out there that would need to be fulfilled; 0 for geostationary, 51.6 for ISS (assuming it's still up when we build the loop), 80-90 for various Earth observation and communication satellites. If we can super cheaply launch satellites into a couple defined inclinations most customers would probably be able to make do with one of these common inclinations rather than today where they'd go with the perfect one.

blauditore 8y ago

If hauling mass into orbit relatively cheaply would be possible, wouldn't it be easy to just send along a counter-mass (or actually a second useful item) and split them when in orbit (e.g. with some explosives)? So you would end up with two symmetrically orbiting items, but without having to deal with rocket propellants.

ithkuil 8y ago
so basically a "rocket" (two rockets?) with a high reaction mass?
CompelTechnic 8y ago
Low earth orbit is at a speed of 28,080 km/h. If you want to separate the two halves of your satelite at a significant angle from their starting trajectory, you have to provide a lot of impulse perpendicular to the direction of travel (or from a zero-orbital speed vertical launch at apogee, which would be weird). More impulse than an explosion could make, probably even if you built your satellite like a brick shithouse. Rockets conveniently spread the impulse out over a long period of time.

paulmd 8y ago

Changing inclination costs a lot because dV costs a lot. If you can easily bring hundreds of tons of fuel to orbit, that's no longer the case. The launch loop changes everything, because your launch costs are in the neighborhood of $3 per kg. That's a total shift in the way we think about rocketry. Imagine if gasoline was $4000 a gallon. In that world, driving 20 miles to the store to pick up some groceries would be unthinkable.