3 ms·

SSTOs trade-off is very unfavorable, which is why no one is seriously considering one anymore, for Earth's gravity well. In order to avoid solving the relative

SSTOs trade-off is very unfavorable, which is why no one is seriously considering one anymore, for Earth's gravity well. In order to avoid solving the relative simple task of efficient stage mating and assembly, an engineering challenge you have to solve once per launch system and can amortize over the whole life of the system, you end up paying the cost of hauling into orbit a huge amount of unnecessary mass, every single launch. That's a very expensive trade-off.

evgen 6y ago
To take the fanboy's pride as an example, how much time is spent taking a Falcon first stage from landing to re-launch? Days? Weeks? Months? If you are expecting to use your launch infrastructure the same way we use a large commercial airliner then this isn't good enough. An SSTO could launch, orbit, return, refuel, and re-launch in the same day. For high-value cargo where the mass it not too much (c.f. humans) this might actually make sense.
- erispoe 6y ago
  It take 2 to 3 days to reach the ISS from the ground. Getting to orbit is only 8min of that. The rest is a slow approach of the station. If you want to deliver cargo or people to a specific orbit and a specific place, say the ISS, you're not gonna be able to turnover a SSTO in a day. Even a week might not be enough for a quick return trip to and from the ISS. All this time your expensive ground to orbit capacity is idle. A first stage can launch a second stage into orbit and return to launch site in less than 15min. How fast you can turn it around for relaunch is an engineering challenge, but there's no fundamental reason you couldn't do it in a day or even in an hour.
  - mandevil 6y ago
    Note that two day approaches are not a real requirement, it's a choice that is made for operational flexibility. On Gemini 11 all the way back in 1966 NASA demonstrated docking a mere 94 minutes after launch (essentially one orbit). However, the launch window for that flight was two seconds, which is ... not ideal. By planning for a several day approach you give yourself a several hour launch window, which is much more workable. There is another reason for the leisurely approach for manned spacecraft. Studies have shown that something like 75% of spacefarers suffer from Space Acclimatization Sickness, generally lasting 1-3 days before your body gets used to zero-gee and you are fine. A leisurely approach lets an astronaut deal with that phase NOT in the shared space station that spends decades in outer space, but in the capsule which will be coming back down in a few months. SAS is a major limitation on space tourism, incidentally. You'll notice that there are very few plans between 15 minute suborbital hops and two weeks in space: that's because if even trained, physically fit astronauts take 1-3 days to adapt to space, no one is sure what a person who is not as trained will do, and if the word of mouth is "I went into space for three days and felt sick the entire time" that's not a good customer experience.
    - rbanffy 6y ago
      I guess that by the time we get to serious space tourism, we'll have a rotating station with centrifugal gravity.
      - dmd 6y ago
        But then you can no longer look out the window without puking.
        rbanffy 6y ago
        For that you take the elevator to the observatory.
- mumblemumble 6y ago
  The cost/benefit formula you're proposing works out most in SSTO's favor if you literally have just one one launch vehicle, but you're using it constantly. If you're allowed to have more than one launch vehicle, though, and can interleave their usage, then that gives you a lot more options for how to maintain throughput while controlling costs. Oftentimes the optimal solution to a multivariate problem ends up looking decidedly sub-optimal when you focus on just one variable at a time. Also, YAGNI. Right now, it's not certain that we will ever see a time when trips to space are as commonplace as commercial flights. It's far enough off that, even if we take for the sake of argument that it does eventually happen, there's no particular reason to believe that the vehicles we use to do it will be chemical rockets.
  - rbanffy 6y ago
    > there's no particular reason to believe that the vehicles we use to do it will be chemical rockets. That too. If we get sci-fi grade engines, anything can be SSTO.
    - deleted 6y ago
      [deleted]
- DennisP 6y ago
  SpaceX claims Starship/Superheavy will be able to launch the first stage thirty times a day and second stage three times a day. I guess we'll see how that works out.

evgen 6y ago

To take the fanboy's pride as an example, how much time is spent taking a Falcon first stage from landing to re-launch? Days? Weeks? Months? If you are expecting to use your launch infrastructure the same way we use a large commercial airliner then this isn't good enough. An SSTO could launch, orbit, return, refuel, and re-launch in the same day. For high-value cargo where the mass it not too much (c.f. humans) this might actually make sense.

erispoe 6y ago
It take 2 to 3 days to reach the ISS from the ground. Getting to orbit is only 8min of that. The rest is a slow approach of the station. If you want to deliver cargo or people to a specific orbit and a specific place, say the ISS, you're not gonna be able to turnover a SSTO in a day. Even a week might not be enough for a quick return trip to and from the ISS. All this time your expensive ground to orbit capacity is idle. A first stage can launch a second stage into orbit and return to launch site in less than 15min. How fast you can turn it around for relaunch is an engineering challenge, but there's no fundamental reason you couldn't do it in a day or even in an hour.
- mandevil 6y ago
  Note that two day approaches are not a real requirement, it's a choice that is made for operational flexibility. On Gemini 11 all the way back in 1966 NASA demonstrated docking a mere 94 minutes after launch (essentially one orbit). However, the launch window for that flight was two seconds, which is ... not ideal. By planning for a several day approach you give yourself a several hour launch window, which is much more workable. There is another reason for the leisurely approach for manned spacecraft. Studies have shown that something like 75% of spacefarers suffer from Space Acclimatization Sickness, generally lasting 1-3 days before your body gets used to zero-gee and you are fine. A leisurely approach lets an astronaut deal with that phase NOT in the shared space station that spends decades in outer space, but in the capsule which will be coming back down in a few months. SAS is a major limitation on space tourism, incidentally. You'll notice that there are very few plans between 15 minute suborbital hops and two weeks in space: that's because if even trained, physically fit astronauts take 1-3 days to adapt to space, no one is sure what a person who is not as trained will do, and if the word of mouth is "I went into space for three days and felt sick the entire time" that's not a good customer experience.
  - rbanffy 6y ago
    I guess that by the time we get to serious space tourism, we'll have a rotating station with centrifugal gravity.
    - dmd 6y ago
      But then you can no longer look out the window without puking.
      - rbanffy 6y ago
        For that you take the elevator to the observatory.
mumblemumble 6y ago
The cost/benefit formula you're proposing works out most in SSTO's favor if you literally have just one one launch vehicle, but you're using it constantly. If you're allowed to have more than one launch vehicle, though, and can interleave their usage, then that gives you a lot more options for how to maintain throughput while controlling costs. Oftentimes the optimal solution to a multivariate problem ends up looking decidedly sub-optimal when you focus on just one variable at a time. Also, YAGNI. Right now, it's not certain that we will ever see a time when trips to space are as commonplace as commercial flights. It's far enough off that, even if we take for the sake of argument that it does eventually happen, there's no particular reason to believe that the vehicles we use to do it will be chemical rockets.
- rbanffy 6y ago
  > there's no particular reason to believe that the vehicles we use to do it will be chemical rockets. That too. If we get sci-fi grade engines, anything can be SSTO.
  - deleted 6y ago
    [deleted]
DennisP 6y ago
SpaceX claims Starship/Superheavy will be able to launch the first stage thirty times a day and second stage three times a day. I guess we'll see how that works out.