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Are we heading for some science fiction future where no one speaks honestly? It isn't a far stretch to imagine that everything is already recorded and what migh

by sosuke 11y ago

Are we heading for some science fiction future where no one speaks honestly? It isn't a far stretch to imagine that everything is already recorded and what might not be usable against you today could be usable tomorrow if the climate changes. Frightening train of thought, I'll disembark now.

fallingfrog 11y ago
We're already there, friend, and have been for some time.
- AndyNemmity 11y ago
  Very true. The comments I have made in this thread already feel to me as they've crossed a line I shouldn't cross, and I haven't said anything all that meaningful or impactful. That's the fear of being truthful at all.
icedata 11y ago
Have you been watching the Primary campaigns?
mikeash 11y ago
This honesty reveals a lot of problematic stuff about this person. Just taking one random example, if he honestly believes that SES-9 required 100,000 pounds of fuel to make its landing attempt, should he really be part of the upper management of a rocket company? If he thinks their most threatening competitor is "doing nothing," does that maybe suggest he's unsuitable for his position?
- michaelkeenan 11y ago
  > if he honestly believes that SES-9 required 100,000 pounds of fuel to make its landing attempt, should he really be part of the upper management of a rocket company? What is the correct amount of fuel used to make the landing attempt? I just googled and didn't quickly find it, though I did find this speculation at StackExchange[0] talking about reserving 15% of the fuel, or 66 tons, for the landing. 66 tons is 132,000 pounds, so 100,000 pounds seems a reasonable rounding - what am I missing? (I don't know anything about rockets.) [0] http://space.stackexchange.com/questions/4466/how-is-spacex-going-to-land-their-falcon-first-stage http://space.stackexchange.com/questions/4466/how-is-spacex-...
  - mikeash 11y ago
    First, a quick overview on how the landing works. After the first stage separates, it executes a "boostback burn," using the engines to get it moving toward the landing site. Sometime later, it fires the engines again as part of the "reentry burn," which is used to soften the blow of hitting the atmosphere at Mach Whatever. Apparently the rocket exhaust acts a little bit like an ad hoc heat shield, plus it helps slow the thing down. Finally, right as it approaches the landing site, it fires the center engine a final time to, hopefully, bring the rocket to a stop at zero altitude. The amount of fuel used varies a lot, because they can land in different places. At one extreme, you have a landing at the launch site, which uses the most fuel in order to get the first stage turned around and coming back. Barge landings use less fuel, because they can be positioned under the flight path so the rocket doesn't have to maneuver as much. SES-9 was at the other extreme. It reserved the bare minimum of fuel for the landing attempt because of its heavy, high-performance payload. That meant no maneuvering boostback burn, no or minimal reentry burn, and the landing burn itself was done with three engines instead of the typical one. That saves fuel because the rocket decelerates faster and spends less time fighting gravity, but of course the control challenge is magnified, which is probably why it went all explodey. Putting some numbers on it, I found some estimates here: https://www.reddit.com/r/spacex/comments/2vuy1v/how_much_fuel_do_the_boost_back_reentry_and/ https://www.reddit.com/r/spacex/comments/2vuy1v/how_much_fue... According to that, landing at the launch site would require about 38 tons of fuel, and a (normal) barge landing would require about 20 tons. SES-9's barge landing would have been even less. I believe the 15% from your StackExchange link is confused, and someone mistook the payload penalty (about 15% for a barge landing) for the amount of fuel required.
    - TrevorJ 11y ago
      38 tons for RTLS is 76,000 pounds, so the figure isn't really all that exaggerated for the worst case. In any case, the fuel is cheap relative to everything else so as long as they can put the payload on orbit expending almost any amount of fuel to recover the rocket is perfectly reasonable. Not sure why the ULA guy thought spending 100,000 of fuel to recover a 15 million dollar core would be a bad thing.
- AndyNemmity 11y ago
  It's an opinion. New evidence changes opinions. You heard the candid opinion of a man at a given point of time. It doesn't mean he's unsuitable for his position. What makes him unsuitable for his position is that he thought he could discuss it with students. The tenor and his thoughts I've heard from all sorts of businesses with relevant detail in their fields. This is an accurate portrayal of all of those conversations.
  - mikeash 11y ago
    There are both opinions and facts in there. A person is entitled to his own opinions, but they are not entitled to their own facts.
    - AndyNemmity 11y ago
      I agree with your comment entirely. I guess the difference we're dancing around is that I am so often hearing people be wrong tactically, and right tactically, and all over in between that I don't think negatively about someone being wrong. Being wrong is a constant in complex situations, and what matters is correcting and moving on. If we take just the last year, I've been wrong a breathtaking amount of time, as has everyone else I've ever discussed with. It happens, and you're constantly trying to move yourself closer to truth.

by sosuke 11y ago

fallingfrog 11y ago

We're already there, friend, and have been for some time.

AndyNemmity 11y ago
Very true. The comments I have made in this thread already feel to me as they've crossed a line I shouldn't cross, and I haven't said anything all that meaningful or impactful. That's the fear of being truthful at all.

icedata 11y ago

Have you been watching the Primary campaigns?

mikeash 11y ago

This honesty reveals a lot of problematic stuff about this person. Just taking one random example, if he honestly believes that SES-9 required 100,000 pounds of fuel to make its landing attempt, should he really be part of the upper management of a rocket company? If he thinks their most threatening competitor is "doing nothing," does that maybe suggest he's unsuitable for his position?

michaelkeenan 11y ago
> if he honestly believes that SES-9 required 100,000 pounds of fuel to make its landing attempt, should he really be part of the upper management of a rocket company? What is the correct amount of fuel used to make the landing attempt? I just googled and didn't quickly find it, though I did find this speculation at StackExchange[0] talking about reserving 15% of the fuel, or 66 tons, for the landing. 66 tons is 132,000 pounds, so 100,000 pounds seems a reasonable rounding - what am I missing? (I don't know anything about rockets.) [0] http://space.stackexchange.com/questions/4466/how-is-spacex-going-to-land-their-falcon-first-stage http://space.stackexchange.com/questions/4466/how-is-spacex-...
- mikeash 11y ago
  First, a quick overview on how the landing works. After the first stage separates, it executes a "boostback burn," using the engines to get it moving toward the landing site. Sometime later, it fires the engines again as part of the "reentry burn," which is used to soften the blow of hitting the atmosphere at Mach Whatever. Apparently the rocket exhaust acts a little bit like an ad hoc heat shield, plus it helps slow the thing down. Finally, right as it approaches the landing site, it fires the center engine a final time to, hopefully, bring the rocket to a stop at zero altitude. The amount of fuel used varies a lot, because they can land in different places. At one extreme, you have a landing at the launch site, which uses the most fuel in order to get the first stage turned around and coming back. Barge landings use less fuel, because they can be positioned under the flight path so the rocket doesn't have to maneuver as much. SES-9 was at the other extreme. It reserved the bare minimum of fuel for the landing attempt because of its heavy, high-performance payload. That meant no maneuvering boostback burn, no or minimal reentry burn, and the landing burn itself was done with three engines instead of the typical one. That saves fuel because the rocket decelerates faster and spends less time fighting gravity, but of course the control challenge is magnified, which is probably why it went all explodey. Putting some numbers on it, I found some estimates here: https://www.reddit.com/r/spacex/comments/2vuy1v/how_much_fuel_do_the_boost_back_reentry_and/ https://www.reddit.com/r/spacex/comments/2vuy1v/how_much_fue... According to that, landing at the launch site would require about 38 tons of fuel, and a (normal) barge landing would require about 20 tons. SES-9's barge landing would have been even less. I believe the 15% from your StackExchange link is confused, and someone mistook the payload penalty (about 15% for a barge landing) for the amount of fuel required.
  - TrevorJ 11y ago
    38 tons for RTLS is 76,000 pounds, so the figure isn't really all that exaggerated for the worst case. In any case, the fuel is cheap relative to everything else so as long as they can put the payload on orbit expending almost any amount of fuel to recover the rocket is perfectly reasonable. Not sure why the ULA guy thought spending 100,000 of fuel to recover a 15 million dollar core would be a bad thing.
AndyNemmity 11y ago
It's an opinion. New evidence changes opinions. You heard the candid opinion of a man at a given point of time. It doesn't mean he's unsuitable for his position. What makes him unsuitable for his position is that he thought he could discuss it with students. The tenor and his thoughts I've heard from all sorts of businesses with relevant detail in their fields. This is an accurate portrayal of all of those conversations.
- mikeash 11y ago
  There are both opinions and facts in there. A person is entitled to his own opinions, but they are not entitled to their own facts.
  - AndyNemmity 11y ago
    I agree with your comment entirely. I guess the difference we're dancing around is that I am so often hearing people be wrong tactically, and right tactically, and all over in between that I don't think negatively about someone being wrong. Being wrong is a constant in complex situations, and what matters is correcting and moving on. If we take just the last year, I've been wrong a breathtaking amount of time, as has everyone else I've ever discussed with. It happens, and you're constantly trying to move yourself closer to truth.