5 ms·

So you want to use system that needs 14 launches to get to the moon to get to mars? Let that sink in... Falcon a much simpler rocket has a reuse window of over

So you want to use system that needs 14 launches to get to the moon to get to mars? Let that sink in... Falcon a much simpler rocket has a reuse window of over a month. How long would it take to re-certify starship for a launch? You are going to need dozens of them launching everyday for months to prep one mission and hoping nothing will go bad. Those kind of missions are complex tasks and complicating things make them more complex and error prone exponentially

mlindner 2y ago
Falcon has a reuse window of less than a month, 21 days in fact. And that's why you use multiple vehicles. Falcon also uses multiple vehicles which is how it achieves flights on average every 3 days so far this year. Also Falcon is inherently harder to reuse because of its fuel choice causing substantial soot buildup on the vehicle that needs to be cleaned away whenever inspections are done both inside the engines and on the vehicle itself. Its fairings also get dunked into sea water every time they're reused which needs to be cleaned off.
avmich 2y ago
So, on that recent presentation Musk talked about around 250,000 tons to Mars in one launch window - every 2 years - which's gonna take ~1000 Starship flights to Mars. So if every flight to Mars needs 10, nah, 15 refueling flights, that means 15,000 Starship flights in 2 years, which is 20 flights a day. Which is way, way less than the commercial aviation is doing today. And btw Starship is way simpler, at least in many places, than Boeing 747. So what's the problem? Re-certify for flight? I can envision an automated procedure which would analyze the data obtained from the rocket in flight and after flight which makes a decision in a split second, just like some systems in cars routinely do. Hoping nothing will go bad? You can get much more risks on unmanned missions. You'll also get numbers on your side, when if something goes wrong you fix it, systematically, for future attempts. That's not exactly just hoping, right?
- withinboredom 2y ago
  > on that recent presentation Musk talked about around 250,000 tons to Mars in one launch window Except there isn't any data to back that up. It took off empty this last time, and didn't have enough fuel to complete it's mission.
  - mlindner 2y ago
    There is no evidence to backup your statement that it didn't have enough fuel to complete it's mission. It intentionally did not go to orbit because they didn't want to risk stranding such a huge vehicle that can withstand re-entry in orbit if its engines were unable to relight. And indeed they did have issues with relighting the engines so that was a very good decision in retrospect. It was an intentional decision not to go into orbit.
    - withinboredom 2y ago
      Um. They showed how much fuel was remaining and it was empty. Just some back of the napkin math shows they used far less delta-v to get to their test flight, with no payload, and ran out of fuel. That doesn’t bode well.
  - avmich 2y ago
    > Except there isn't any data to back that up. There's seemingly no physical - or economical, for that matter - reason for this to be impossible, so why not? Starship definitely didn't complete testing at this point, many things are still ahead of us, but to talk about impossibilities - why? Yes, of course we didn't do that yet, but we're talking about possibilities in the future.
    - withinboredom 2y ago
      You’d expect at least some evidence that it can lift that much weight by this point with a dummy load in the hold. Especially considering that they should be long past that point according to their last updated roadmap.
JumpCrisscross 2y ago
> you want to use system that needs 14 launches to get to the moon to get to mars? Again, the criticisms are valid. But it's unlikely we can get to Mars--repeatedly and sustainably--without mastering in-orbit re-fuelling. So while it isn't technically necessary for a Moon mission, nor even repeated Moon missions, it is for a Moon mission that's building to Mars. (Again, repeatedly--we can do without it [1]. But it's far more expensive in the long run.) > How long would it take to re-certify starship for a launch? Falcon 9 has been turned around in 3 weeks [2]. The bottleneck has thus far been launch pads. If you can cut that to 2 weeks, you need 5 to 7 refuelling Starships ready per launch. Once again, the bottleneck would be launch pads. You and I are on the same page about that re-fuelling overhead being bonkers. It's mostly because SLS and Orion suck. But if the only thing we learn from Artemis is fuel depoting, that's a huge win. > You are going to need dozens of them launching everyday for months to prep one mission and hoping nothing will go bad The timeline for the first propellant-transfer test is three to four weeks. 14 launches over 30 days comes to a launch every other day. Ambitious, but only about twice as frequently as the Falcon family launched in 2023, and for a shorter interval. [1] https://en.wikipedia.org/wiki/Mars_Direct#Second_launch https://en.wikipedia.org/wiki/Mars_Direct#Second_launch [2] https://twitter.com/SpaceX/status/1520155013661659137?ref_src=twsrc^tfw https://twitter.com/SpaceX/status/1520155013661659137?ref_sr...
- avmich 2y ago
  > The timeline for the first propellant-transfer test is three to four weeks. 14 launches over 30 days comes to a launch every other day. Not sure I understand your numbers here in relation to the quoted part?
  - JumpCrisscross 2y ago
    > Not sure I understand your numbers here in relation to the quoted part The unknown variable is in-orbit propellant boil-off. How much propellant will poof away for each day in orbit, and during the propellant transfer. The test next month will observe this for 3 to 4 weeks. So for the actual mission, we will presumably have 3 to 4 weeks to put all the fuel in orbit. Assuming it takes 14 launches to launch that fuel (we won't know the final number until we do the tests), that gives us a required average launch cadence of about 2 days.

mlindner 2y ago

Falcon has a reuse window of less than a month, 21 days in fact. And that's why you use multiple vehicles. Falcon also uses multiple vehicles which is how it achieves flights on average every 3 days so far this year. Also Falcon is inherently harder to reuse because of its fuel choice causing substantial soot buildup on the vehicle that needs to be cleaned away whenever inspections are done both inside the engines and on the vehicle itself. Its fairings also get dunked into sea water every time they're reused which needs to be cleaned off.

avmich 2y ago

So, on that recent presentation Musk talked about around 250,000 tons to Mars in one launch window - every 2 years - which's gonna take ~1000 Starship flights to Mars. So if every flight to Mars needs 10, nah, 15 refueling flights, that means 15,000 Starship flights in 2 years, which is 20 flights a day. Which is way, way less than the commercial aviation is doing today. And btw Starship is way simpler, at least in many places, than Boeing 747. So what's the problem? Re-certify for flight? I can envision an automated procedure which would analyze the data obtained from the rocket in flight and after flight which makes a decision in a split second, just like some systems in cars routinely do. Hoping nothing will go bad? You can get much more risks on unmanned missions. You'll also get numbers on your side, when if something goes wrong you fix it, systematically, for future attempts. That's not exactly just hoping, right?

withinboredom 2y ago
> on that recent presentation Musk talked about around 250,000 tons to Mars in one launch window Except there isn't any data to back that up. It took off empty this last time, and didn't have enough fuel to complete it's mission.
- mlindner 2y ago
  There is no evidence to backup your statement that it didn't have enough fuel to complete it's mission. It intentionally did not go to orbit because they didn't want to risk stranding such a huge vehicle that can withstand re-entry in orbit if its engines were unable to relight. And indeed they did have issues with relighting the engines so that was a very good decision in retrospect. It was an intentional decision not to go into orbit.
  - withinboredom 2y ago
    Um. They showed how much fuel was remaining and it was empty. Just some back of the napkin math shows they used far less delta-v to get to their test flight, with no payload, and ran out of fuel. That doesn’t bode well.
- avmich 2y ago
  > Except there isn't any data to back that up. There's seemingly no physical - or economical, for that matter - reason for this to be impossible, so why not? Starship definitely didn't complete testing at this point, many things are still ahead of us, but to talk about impossibilities - why? Yes, of course we didn't do that yet, but we're talking about possibilities in the future.
  - withinboredom 2y ago
    You’d expect at least some evidence that it can lift that much weight by this point with a dummy load in the hold. Especially considering that they should be long past that point according to their last updated roadmap.

JumpCrisscross 2y ago

> you want to use system that needs 14 launches to get to the moon to get to mars? Again, the criticisms are valid. But it's unlikely we can get to Mars--repeatedly and sustainably--without mastering in-orbit re-fuelling. So while it isn't technically necessary for a Moon mission, nor even repeated Moon missions, it is for a Moon mission that's building to Mars. (Again, repeatedly--we can do without it [1]. But it's far more expensive in the long run.) > How long would it take to re-certify starship for a launch? Falcon 9 has been turned around in 3 weeks [2]. The bottleneck has thus far been launch pads. If you can cut that to 2 weeks, you need 5 to 7 refuelling Starships ready per launch. Once again, the bottleneck would be launch pads. You and I are on the same page about that re-fuelling overhead being bonkers. It's mostly because SLS and Orion suck. But if the only thing we learn from Artemis is fuel depoting, that's a huge win. > You are going to need dozens of them launching everyday for months to prep one mission and hoping nothing will go bad The timeline for the first propellant-transfer test is three to four weeks. 14 launches over 30 days comes to a launch every other day. Ambitious, but only about twice as frequently as the Falcon family launched in 2023, and for a shorter interval. [1] https://en.wikipedia.org/wiki/Mars_Direct#Second_launch https://en.wikipedia.org/wiki/Mars_Direct#Second_launch [2] https://twitter.com/SpaceX/status/1520155013661659137?ref_src=twsrc^tfw https://twitter.com/SpaceX/status/1520155013661659137?ref_sr...

avmich 2y ago
> The timeline for the first propellant-transfer test is three to four weeks. 14 launches over 30 days comes to a launch every other day. Not sure I understand your numbers here in relation to the quoted part?
- JumpCrisscross 2y ago
  > Not sure I understand your numbers here in relation to the quoted part The unknown variable is in-orbit propellant boil-off. How much propellant will poof away for each day in orbit, and during the propellant transfer. The test next month will observe this for 3 to 4 weeks. So for the actual mission, we will presumably have 3 to 4 weeks to put all the fuel in orbit. Assuming it takes 14 launches to launch that fuel (we won't know the final number until we do the tests), that gives us a required average launch cadence of about 2 days.