10 ms·

This might be seen as the tipping point in commercial space ventures. With SpaceX running LEO operations, NASA/Roscosmos can focus on the planets next.

by atroyn 11y ago

rbanffy 11y ago
LEO is the most difficult part. I bet NASA and Roscosmos will have tons of company up there.
- dogma1138 11y ago
  LEO by far isn't the most difficult part, not if you are aiming for moon/inter-planetary transport. LEO is ridiculously easy to get too, The ISS is at 340KM, GEO orbit is 35,000 you can put payload in LEO with "amateur" rockets, GEO/HEO is a completely different story, it's extremely hard and you need a heck of a rocket to do it with any substantial payload. Now from GEO/HEO to anywhere else it's quite easy to get because you are pretty much near the escape velocity so it takes almost no delta-v to get pretty much anywhere you want in the solar system, at least as far as getting to a higher solar orbit goes as the closer you get the faster your solar orbital velocity is so using that speed to get even to the edges of the solar system takes very little energy. If we talk about say a mars shot then most of the energy in that trip goes to 2 things, getting to high earth orbit, and then slowing down for a mars capture the amount of fuel needed to do the martian orbit transfer is almost negligible.
  - mikeash 11y ago
    What amateur rockets can put payload into LEO?
    - dogma1138 11y ago
      https://en.wikipedia.org/wiki/Civilian_Space_eXploration_Team https://en.wikipedia.org/wiki/Civilian_Space_eXploration_Tea... Their "go fast rocket" got to about half the altitude of Sputnik so if you got the cash you don't need to scale "go fast rocket" up by that much to put a cube-sat / micro-satellite up there.
      - fivesigma 11y ago
        The difference between such a ballistic trajectory (1/5th of escape velocity) and LEO is huge. >you don't need to scale "go fast rocket" up by that much My napkin math says you need at least 2 orders of magnitude more fuel mass which classifies as "a lot"
        dogma1138 11y ago
        Not sure what your math is, but mine is about 20% larger rocket to get to 160KM and have enough speed for orbit, at least as far as cube-sats that can skip on the atmosphere for a bit go. There's also https://en.wikipedia.org/wiki/Copenhagen_Suborbitals https://en.wikipedia.org/wiki/Copenhagen_Suborbitals with their plans for a manned suborbital flight, their rocket (although it blew up) could also be used as a base for amateur orbital flights. I'm not entirely sure what is so surprising here, it's a question of money at this point, but amateur rockets are quick close to being able to reach space, this doesn't mean that they will be commercial viable or even viable for any non-anecdotal use.
        avmich 11y ago
        LEO difficulty is mostly speed, not height. SpaceShipOne flew above 100 km - but it's a long way to reach Vostok-1 performance, as delta-V for SS1 is more than four times less than for Vostok-1.
        mikeash 11y ago
        What's surprising is that amateur rockets can reach space on suborbital trajectories but none of them come even remotely close to orbit. Altitude is the easy part, relatively speaking. Getting the speed for LEO is the hard part. The GoFast rocket you linked to has demonstrated up to 4,200MPH. Low earth orbit requires about 17,000MPH. That factor of ~4 requires massively larger rockets, because the rocket equation is cruel. Each incremental increase in final speed requires an exponential (actually using this word correctly, for once) increase in the amount of fuel. Fuel in return requires more hardware like tanks and engines, which means yet more fuel is required, etc. Edit: using RP-1 as the fuel in a single stage, getting to 4,200MPH requires that 45% of your total rocket mass be fuel at launch. Getting to LEO requires 94% of the mass to be fuel.
    - deleted 11y ago
      [deleted]
  - jccooper 11y ago
    The concept of LEO being "ridiculously easy to get too" is mad. No amateur rocket has made orbit or even come close. The difficulty of building a vehicle to make LEO is not comparable to building one to raise altitude once in orbit. LEO to GEO is less than half the delta-v of surface to LEO. It is routinely done by satellites alone. The only reason getting to GEO is particularly hard is because you have to get to LEO first. You are right about transfer to Mars, though.
- rquantz 11y ago
  LEO is the most expensive part, but we know how to do it pretty well at this point. Landing something big enough to carry humans on Mars, on the other hand, is a problem we haven't solved yet.
  - rbanffy 11y ago
    Landing won't be the hardest part - any Earth-rated capsule with rockets like the human-rated Dragon can do the last leg provided you are leaving Martian orbit with some rocket to slow you down. You may need parachutes to slow the craft to the point the rockets can make their part. Curiosity was complicated because they didn't want to touchdown on rockets. Now, accelerating a Mir-sized craft towards Mars and decelerating it to orbit while keeping the crew alive for a year outside the Earth's benevolent magnetic field and having enough fuel to accelerate back to Earth (even assuming we'll throw out the interplanetary craft and get to Earth on a capsule) is quite an impressive engineering feat. I'm inclined to suggest that, instead of building a vehicle like that we build one or more cyclers that will orbit the Earth-Mars-Sun system periodically and astronauts would only need to reach them in order to get back and forth. This way we pack all shielding for the long-duration trip into the cyclers and astronauts only need to carry the consumables they'll use. Since reaching them would be time-critical (they won't stop), I would suggest building a similar one that could be stationed in Martian orbit to serve as a fallback plan in case a crew misses the one cycler and has to wait a couple months for the next bus home. These two spacecraft are, essentially, space stations with clever orbits we could maintain with regular resupply missions just as we do with the ISS, but we'd need beefier rockets because the delta-v is the same as a craft going to Mars (because that's what it's doing). Luckily, we'd only need to accelerate the resupply craft - living space is "free" after the first burn. I am uncertain if these craft are more or less complicated than building and landing the Mars ascent vehicle (much worse than landing a crew capsule, for sure). This sounds very complicated to me.
    - redahs 11y ago
      > accelerating a Mir-sized craft towards Mars and decelerating it to orbit while keeping the crew alive ... and having enough fuel to accelerate back to Earth ... You don't need to ship enough fuel to return to Earth in the same trip as a manned crew. You can send orbital depots for return fuel and ascent\descent vehicles ahead of time in unmanned missions. This could be done multiple years in advance. When you are launching the crew and interplanetary habitat, you only need to bring enough fuel for a one way trip.
pjscott 11y ago
Good news on that! The Falcon Heavy is tentatively scheduled to have its first flight in April-May 2016. The Dragon v2 capsule is designed for powered landings, which is how the in-flight abort thing works. Combine the two, and fiddle with the configuration a bit, and you can land in a whole lot of desirable parts of the solar system. Want to send a Mars rover? They're calculating that they can deliver 2-4 tons of payload to the surface of Mars. Want to send an unmanned mission to the moon, or Europa? Ditch the parachutes and add extra propellant to make up for the lack of aerobraking. And so on -- it could be an incredible boon for planetary science.

This might be seen as the tipping point in commercial space ventures. With SpaceX running LEO operations, NASA/Roscosmos can focus on the planets next.

by atroyn 11y ago

This might be seen as the tipping point in commercial space ventures. With SpaceX running LEO operations, NASA/Roscosmos can focus on the planets next.

rbanffy 11y ago

LEO is the most difficult part. I bet NASA and Roscosmos will have tons of company up there.

dogma1138 11y ago
LEO by far isn't the most difficult part, not if you are aiming for moon/inter-planetary transport. LEO is ridiculously easy to get too, The ISS is at 340KM, GEO orbit is 35,000 you can put payload in LEO with "amateur" rockets, GEO/HEO is a completely different story, it's extremely hard and you need a heck of a rocket to do it with any substantial payload. Now from GEO/HEO to anywhere else it's quite easy to get because you are pretty much near the escape velocity so it takes almost no delta-v to get pretty much anywhere you want in the solar system, at least as far as getting to a higher solar orbit goes as the closer you get the faster your solar orbital velocity is so using that speed to get even to the edges of the solar system takes very little energy. If we talk about say a mars shot then most of the energy in that trip goes to 2 things, getting to high earth orbit, and then slowing down for a mars capture the amount of fuel needed to do the martian orbit transfer is almost negligible.
- mikeash 11y ago
  What amateur rockets can put payload into LEO?
  - dogma1138 11y ago
    https://en.wikipedia.org/wiki/Civilian_Space_eXploration_Team https://en.wikipedia.org/wiki/Civilian_Space_eXploration_Tea... Their "go fast rocket" got to about half the altitude of Sputnik so if you got the cash you don't need to scale "go fast rocket" up by that much to put a cube-sat / micro-satellite up there.
    - fivesigma 11y ago
      The difference between such a ballistic trajectory (1/5th of escape velocity) and LEO is huge. >you don't need to scale "go fast rocket" up by that much My napkin math says you need at least 2 orders of magnitude more fuel mass which classifies as "a lot"
      - dogma1138 11y ago
        Not sure what your math is, but mine is about 20% larger rocket to get to 160KM and have enough speed for orbit, at least as far as cube-sats that can skip on the atmosphere for a bit go. There's also https://en.wikipedia.org/wiki/Copenhagen_Suborbitals https://en.wikipedia.org/wiki/Copenhagen_Suborbitals with their plans for a manned suborbital flight, their rocket (although it blew up) could also be used as a base for amateur orbital flights. I'm not entirely sure what is so surprising here, it's a question of money at this point, but amateur rockets are quick close to being able to reach space, this doesn't mean that they will be commercial viable or even viable for any non-anecdotal use.
        avmich 11y ago
        LEO difficulty is mostly speed, not height. SpaceShipOne flew above 100 km - but it's a long way to reach Vostok-1 performance, as delta-V for SS1 is more than four times less than for Vostok-1.
        mikeash 11y ago
        What's surprising is that amateur rockets can reach space on suborbital trajectories but none of them come even remotely close to orbit. Altitude is the easy part, relatively speaking. Getting the speed for LEO is the hard part. The GoFast rocket you linked to has demonstrated up to 4,200MPH. Low earth orbit requires about 17,000MPH. That factor of ~4 requires massively larger rockets, because the rocket equation is cruel. Each incremental increase in final speed requires an exponential (actually using this word correctly, for once) increase in the amount of fuel. Fuel in return requires more hardware like tanks and engines, which means yet more fuel is required, etc. Edit: using RP-1 as the fuel in a single stage, getting to 4,200MPH requires that 45% of your total rocket mass be fuel at launch. Getting to LEO requires 94% of the mass to be fuel.
  - deleted 11y ago
    [deleted]
- jccooper 11y ago
  The concept of LEO being "ridiculously easy to get too" is mad. No amateur rocket has made orbit or even come close. The difficulty of building a vehicle to make LEO is not comparable to building one to raise altitude once in orbit. LEO to GEO is less than half the delta-v of surface to LEO. It is routinely done by satellites alone. The only reason getting to GEO is particularly hard is because you have to get to LEO first. You are right about transfer to Mars, though.
rquantz 11y ago
LEO is the most expensive part, but we know how to do it pretty well at this point. Landing something big enough to carry humans on Mars, on the other hand, is a problem we haven't solved yet.
- rbanffy 11y ago
  Landing won't be the hardest part - any Earth-rated capsule with rockets like the human-rated Dragon can do the last leg provided you are leaving Martian orbit with some rocket to slow you down. You may need parachutes to slow the craft to the point the rockets can make their part. Curiosity was complicated because they didn't want to touchdown on rockets. Now, accelerating a Mir-sized craft towards Mars and decelerating it to orbit while keeping the crew alive for a year outside the Earth's benevolent magnetic field and having enough fuel to accelerate back to Earth (even assuming we'll throw out the interplanetary craft and get to Earth on a capsule) is quite an impressive engineering feat. I'm inclined to suggest that, instead of building a vehicle like that we build one or more cyclers that will orbit the Earth-Mars-Sun system periodically and astronauts would only need to reach them in order to get back and forth. This way we pack all shielding for the long-duration trip into the cyclers and astronauts only need to carry the consumables they'll use. Since reaching them would be time-critical (they won't stop), I would suggest building a similar one that could be stationed in Martian orbit to serve as a fallback plan in case a crew misses the one cycler and has to wait a couple months for the next bus home. These two spacecraft are, essentially, space stations with clever orbits we could maintain with regular resupply missions just as we do with the ISS, but we'd need beefier rockets because the delta-v is the same as a craft going to Mars (because that's what it's doing). Luckily, we'd only need to accelerate the resupply craft - living space is "free" after the first burn. I am uncertain if these craft are more or less complicated than building and landing the Mars ascent vehicle (much worse than landing a crew capsule, for sure). This sounds very complicated to me.
  - redahs 11y ago
    > accelerating a Mir-sized craft towards Mars and decelerating it to orbit while keeping the crew alive ... and having enough fuel to accelerate back to Earth ... You don't need to ship enough fuel to return to Earth in the same trip as a manned crew. You can send orbital depots for return fuel and ascent\descent vehicles ahead of time in unmanned missions. This could be done multiple years in advance. When you are launching the crew and interplanetary habitat, you only need to bring enough fuel for a one way trip.

pjscott 11y ago

Good news on that! The Falcon Heavy is tentatively scheduled to have its first flight in April-May 2016. The Dragon v2 capsule is designed for powered landings, which is how the in-flight abort thing works. Combine the two, and fiddle with the configuration a bit, and you can land in a whole lot of desirable parts of the solar system. Want to send a Mars rover? They're calculating that they can deliver 2-4 tons of payload to the surface of Mars. Want to send an unmanned mission to the moon, or Europa? Ditch the parachutes and add extra propellant to make up for the lack of aerobraking. And so on -- it could be an incredible boon for planetary science.