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>The Government Accountability Office’s preliminary findings reveal a pattern of problems with turbine blades that pump fuel into rocket engines >The crack-pro

by skolos 10y ago

>The Government Accountability Office’s preliminary findings reveal a pattern of problems with turbine blades that pump fuel into rocket engines >The crack-prone parts are considered a potentially major threat to rocket safety, the industry officials said, and may require redesign of what are commonly called the Falcon 9’s turbopumps. >A SpaceX spokesman said “we have qualified our engines to be robust” to such cracks but are “modifying the design to avoid them altogether.” The pending changes “will be part of the final design” for the Falcon 9, he added, “in partnership with NASA to qualify engines for manned spaceflight.”

skolos 10y ago
Another interesting bit: >For Boeing, these officials said, GAO investigators—among other items—raised questions about the status of tests to determine the reliability of its parachute systems designed to help returning manned capsules land safely. >The GAO also has determined that both companies face an uphill struggle to meet NASA’s statistical goal of no more than one projected astronaut fatality in 270 flights, industry officials said.
- c3534l 10y ago
  That's a weirdly specific, yet round number.
  - saalweachter 10y ago
    I suspect it is not so much round as rounded. You don't really need more than two significant figures for the number.
  - zellyn 10y ago
    My "expected value" knowledge has atrophied, but I'm guessing this is just a weird way of saying a success rate of 99.5% or something. 0.995^135 is about 0.5, so you blow up on average half the time in 135 flights, or once every 270 flights.
    - froindt 10y ago
      > no more than one projected astronaut fatality in 270 flights > success rate of 99.5% or something. 0.995^135 is about 0.5 Method seems pretty good, but unfortunately that math would only work if there was exactly one astronaut per flight. Per Wikipedia, the capacity is up to 7 crew members, so I reckon at full capacity, that would be 1 full vehicle failure with 7 lives lost in 1,890 flights. My math is a bit rusty too though. https://en.wikipedia.org/wiki/Dragon_2 https://en.wikipedia.org/wiki/Dragon_2
      - Already__Taken 10y ago
        Not a rocket buff but I thought the soyuz rocket (R-7) was one of the most proven and reliable rockets there are. In 60 years that family has had 1,859 launches[1]. So statistics aside it's interesting just how high those standards are if you bore them out. Going to look stupid with some maths here; If spacex launch every 2 weeks which I thought was the goal, that's like 72 years to prove that reliability record. 72.69 = (1890 * 2) / 52 Number of 1 week periods divided by weeks in a year. 1: https://en.wikipedia.org/wiki/R-7_(rocket_family)#Summary_of_variants https://en.wikipedia.org/wiki/R-7_(rocket_family)#Summary_of...
- merpnderp 10y ago
  Wasn't NASA's record with the space shuttle more like 1 in 2.5 fatalities per flight? 14 fatalities in 135 launches? Must have been good enough for government work.
  - jackmott 10y ago
    with modern material and computation advances it would be reasonable to raise the bar
    - merpnderp 10y ago
      They're asking for nearly 2 magnitudes better safety than they could provide. Granted the space shuttle was dumb from the beginning and we'd be flying around in our flying cars and vacationing on Mars if they'd stuck with the far superior Saturn launch system. But who could of known that, besides the plethora of scientists who pointed this out?
      - bsder 10y ago
        Except that the options at the time were space shuttle or NOTHING--not space shuttle or Saturn V. NASA threw in with the only folks willing to fund spaceflight--the military. And the military demanded an orbiter that could do circumpolar orbits--which was totally crazy from an engineering standpoint.
        colordrops 10y ago
        What does it mean for an orbiter to support circumpolar orbits, and why is it crazy?
        Arnt 10y ago
        It means being able to reach more kinds of orbits, which adds requirements. So does reentry capability. Why add those two sets of requirements to the same vehicle, see?
        10y ago

by skolos 10y ago

skolos 10y ago

Another interesting bit: >For Boeing, these officials said, GAO investigators—among other items—raised questions about the status of tests to determine the reliability of its parachute systems designed to help returning manned capsules land safely. >The GAO also has determined that both companies face an uphill struggle to meet NASA’s statistical goal of no more than one projected astronaut fatality in 270 flights, industry officials said.

c3534l 10y ago
That's a weirdly specific, yet round number.
- saalweachter 10y ago
  I suspect it is not so much round as rounded. You don't really need more than two significant figures for the number.
- zellyn 10y ago
  My "expected value" knowledge has atrophied, but I'm guessing this is just a weird way of saying a success rate of 99.5% or something. 0.995^135 is about 0.5, so you blow up on average half the time in 135 flights, or once every 270 flights.
  - froindt 10y ago
    > no more than one projected astronaut fatality in 270 flights > success rate of 99.5% or something. 0.995^135 is about 0.5 Method seems pretty good, but unfortunately that math would only work if there was exactly one astronaut per flight. Per Wikipedia, the capacity is up to 7 crew members, so I reckon at full capacity, that would be 1 full vehicle failure with 7 lives lost in 1,890 flights. My math is a bit rusty too though. https://en.wikipedia.org/wiki/Dragon_2 https://en.wikipedia.org/wiki/Dragon_2
    - Already__Taken 10y ago
      Not a rocket buff but I thought the soyuz rocket (R-7) was one of the most proven and reliable rockets there are. In 60 years that family has had 1,859 launches[1]. So statistics aside it's interesting just how high those standards are if you bore them out. Going to look stupid with some maths here; If spacex launch every 2 weeks which I thought was the goal, that's like 72 years to prove that reliability record. 72.69 = (1890 * 2) / 52 Number of 1 week periods divided by weeks in a year. 1: https://en.wikipedia.org/wiki/R-7_(rocket_family)#Summary_of_variants https://en.wikipedia.org/wiki/R-7_(rocket_family)#Summary_of...
merpnderp 10y ago
Wasn't NASA's record with the space shuttle more like 1 in 2.5 fatalities per flight? 14 fatalities in 135 launches? Must have been good enough for government work.
- jackmott 10y ago
  with modern material and computation advances it would be reasonable to raise the bar
  - merpnderp 10y ago
    They're asking for nearly 2 magnitudes better safety than they could provide. Granted the space shuttle was dumb from the beginning and we'd be flying around in our flying cars and vacationing on Mars if they'd stuck with the far superior Saturn launch system. But who could of known that, besides the plethora of scientists who pointed this out?
    - bsder 10y ago
      Except that the options at the time were space shuttle or NOTHING--not space shuttle or Saturn V. NASA threw in with the only folks willing to fund spaceflight--the military. And the military demanded an orbiter that could do circumpolar orbits--which was totally crazy from an engineering standpoint.
      - colordrops 10y ago
        What does it mean for an orbiter to support circumpolar orbits, and why is it crazy?
        Arnt 10y ago
        It means being able to reach more kinds of orbits, which adds requirements. So does reentry capability. Why add those two sets of requirements to the same vehicle, see?
        10y ago