3 ms·

The BFS is part of the whole stack, it is the second stage. It is unclear because of lack of technical specification from SpaceX but at the moment it seems unli

The BFS is part of the whole stack, it is the second stage. It is unclear because of lack of technical specification from SpaceX but at the moment it seems unlikely that the BFB will fly without the BFS. So you can't look at the BFS as a separate thing as you are implying, it is a core part of the architecture. It'd be like saying that the Saturn V can haul x amount of payload in addition to its second stage.

mikeash 8y ago
You can’t ignore it either. The BFS isn’t a useless hunk of metal once it’s in orbit, it’s still very useful. Consider a past example. The Space Shuttle’s payload to orbit was many times smaller than Saturn V’s. Yet the Shuttle could do missions over two weeks long with seven crew, far more than Apollo could. How is that possible? Because the orbiter didn’t count as part of the “payload”. BFR is going to send 8 people on a trip around the moon. Saturn V couldn’t do that, even though it could orbit more “payload.” It all depends on the mission. If you just want to put satellites in orbit, Saturn V is more capable (ignoring costs). If you want to send people somewhere, BFR is way more capable. BFR can put a lot more mass into orbit, it’s just that a lot of that mass is taken up by mandatory stuff. If that stuff is useful for you then it should count. If it’s not then it shouldn’t. And that brings us back to my original point, way up there, that BFR is major overkill for a satellite launcher, but makes perfect sense for a Mars mission.
- maxerickson 8y ago
  The trip to the moon is great, but it's 2 launches.
  - mikeash 8y ago
    Is it? The mission profile shown during the presentation makes no mention of that. It also shows only 30 minutes in orbit before the lunar injection burn, which wouldn’t be enough to refuel from a tanker.
- computerex 8y ago
  Saturn V and Apollo were designed for a very specific purpose. And so the CSM could only sustain the crew for the trip to the moon. The 310k lbs payload did not include the CSM and LEM. In theory the Saturn V booster could haul up a BFS style ship if such a thing existed.
  - mikeash 8y ago
    “The 310k lbs payload did not include the CSM and LEM.” Are you saying the Saturn V was able to lift 310k lbs plus the CSM and LEM? I’m pretty sure that not true. Saturn V was a general purpose rocket. It wasn’t tied to Apollo, as evidenced by Skylab. It just worked out that nobody found a cost-effective use for it beyond Apollo and Skylab.
    - computerex 8y ago
      Sorry for the confusion, I meant that the Saturn V could haul 310k lbs and the payload didn't necessarily need be the CSM/LEM. So in theory they could attach a dragon/bfs type thing as payload.
      - mikeash 8y ago
        I see. You’re right that it could. It wouldn’t be as good, though, since the BFR’s total mass to orbit is greater. That’s why I’m saying you need to take BFS into account and not just look at “payload” numbers.

mikeash 8y ago

You can’t ignore it either. The BFS isn’t a useless hunk of metal once it’s in orbit, it’s still very useful. Consider a past example. The Space Shuttle’s payload to orbit was many times smaller than Saturn V’s. Yet the Shuttle could do missions over two weeks long with seven crew, far more than Apollo could. How is that possible? Because the orbiter didn’t count as part of the “payload”. BFR is going to send 8 people on a trip around the moon. Saturn V couldn’t do that, even though it could orbit more “payload.” It all depends on the mission. If you just want to put satellites in orbit, Saturn V is more capable (ignoring costs). If you want to send people somewhere, BFR is way more capable. BFR can put a lot more mass into orbit, it’s just that a lot of that mass is taken up by mandatory stuff. If that stuff is useful for you then it should count. If it’s not then it shouldn’t. And that brings us back to my original point, way up there, that BFR is major overkill for a satellite launcher, but makes perfect sense for a Mars mission.

maxerickson 8y ago
The trip to the moon is great, but it's 2 launches.
- mikeash 8y ago
  Is it? The mission profile shown during the presentation makes no mention of that. It also shows only 30 minutes in orbit before the lunar injection burn, which wouldn’t be enough to refuel from a tanker.
computerex 8y ago
Saturn V and Apollo were designed for a very specific purpose. And so the CSM could only sustain the crew for the trip to the moon. The 310k lbs payload did not include the CSM and LEM. In theory the Saturn V booster could haul up a BFS style ship if such a thing existed.
- mikeash 8y ago
  “The 310k lbs payload did not include the CSM and LEM.” Are you saying the Saturn V was able to lift 310k lbs plus the CSM and LEM? I’m pretty sure that not true. Saturn V was a general purpose rocket. It wasn’t tied to Apollo, as evidenced by Skylab. It just worked out that nobody found a cost-effective use for it beyond Apollo and Skylab.
  - computerex 8y ago
    Sorry for the confusion, I meant that the Saturn V could haul 310k lbs and the payload didn't necessarily need be the CSM/LEM. So in theory they could attach a dragon/bfs type thing as payload.
    - mikeash 8y ago
      I see. You’re right that it could. It wouldn’t be as good, though, since the BFR’s total mass to orbit is greater. That’s why I’m saying you need to take BFS into account and not just look at “payload” numbers.