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> To the average layman That’s a meaningless yardstick here. People at NASA definitely thought hitting that target was achievable before the speech. > Landin

by Retric 2y ago

> To the average layman That’s a meaningless yardstick here. People at NASA definitely thought hitting that target was achievable before the speech. > Landing on Mars Landing isn’t the issue. Get people there alive and having enough deltaV to get back is.

somenameforme 2y ago
No, NASA also didn't think it was possible at the time. There's an informative little paper here. [1] It only gets more informative from the first sentence, "Mathematical risk analysis was used in Apollo, but it gave unacceptably pessimistic results and was discontinued." By the time of the launch to the Moon NASA's internal estimates were looking at around a 50% chance of success based on Gene Krantz's (mission controller) "Failure is Not an Option" book. It was a mission they dedicated themselves to, and humans have this way of making things happen when we actually set our minds to tasks. A reality that's often been lost in modern times as we have mostly moved away from pursuing, let alone achieving, great things in the real world. One of the many reasons to get humans on Mars. [1] - https://ntrs.nasa.gov/api/citations/20190002249/downloads/20190002249.pdf https://ntrs.nasa.gov/api/citations/20190002249/downloads/20...
- Retric 2y ago
  You’re confusing specific low odds of success for “didn't think it was possible.” The Apollo missions got unbelievably lucky in that none catastrophically failed despite multiple close calls. However, if you’re willing to try multiple times the odds any mission being successful is much better than every mission being successful. IE: Six missions landed on the moon. If they each had independent 50% odds then six heads is a long way from impossible ~1.6%, but at least 1 head is quite likely ~98.4%. I doubt we would have tried for a 6th mission after 5 failures in a row, but the point is definitions of success matter a great deal here. Similarly failures improve odds of success in the future because you learn from mistakes and success means the system is functional eliminating some risks.
  - somenameforme 2y ago
    What I'm demonstrating is that we indeed knew basically nothing. There was no secret tech or expectation of success. Mathematical models doomed the entire idea to failure, and all the way up to the day of the launch people who spent years in a bubble of optimism still didn't really expect more than a 50% chance of success.
    - Retric 2y ago
      > a 50% chance of success. On that specific launch, which is another way of saying they believed the project had a very good chance of having someone walking on the moon. Failure there wouldn’t even mean people died, just that they didn’t walk on the moon and then safely get back on that mission.
      - ANewFormation 2y ago
        That 50% was after years of bubble optimism and actively blinding themselves to data strongly suggestive otherwise. Had the Apollo missions failed you would obviously be arguing, using the exact same data, that they 'knew they never had a chance.'
        Retric 2y ago
        > Had the Apollo missions failed you would obviously be arguing, using the exact same data, that they 'knew they never had a chance.' No, an earlier post argued that 6 successes doesn’t mean the odds of success on every mission was high. “Got unbelievably lucky” https://news.ycombinator.com/item?id=43130343 https://news.ycombinator.com/item?id=43130343 The exact opposite position after 6 failures would be that the odds were good that at least 1 mission would have succeeded. Obviously, things aren’t actually completely independent, but 6 lunar landings could have successfully been completed with a huge range of different odds. 50% odds of success on the first launch isn’t inconsistent with 6 successful launches or 6 failures, it’s just not enough data to really narrow things down.
Robotbeat 2y ago
On the contrary, we can easily get people there alive. What exactly do you think is beyond our capacity to send crew to Mars while still being alive? Crew regularly do year long expeditions on ISS (edited for clarity), with total radiation dose similar to Mars transit (and show no measurable effects of that radiation). Again, I’m addressing the point “getting them there alive”. Unquestionably, we know how to get crew to Mars alive, and even for the full mission duration, radiation isn’t even in the top 10 of the hazards that could actually kill them during the mission. (It’s a long term hazard, comparable to lung cancer if you’re a cigarette smoker.)
- idlewords 2y ago
  No one has ever done a "years long" expedition to ISS, and the radiation flux in transit to Mars, in particular GCR dose, is much higher than experienced on the space station.
  - Robotbeat 2y ago
    I’m well aware, just mistyped. The total equivalent radiation dose on a fast transit to Mars is less than some ISS expeditions. Note that the magnetic field only deflects lower energy galactic cosmic rays which have a lower gyro radius than the real whoppers. The magnetic field is less important to overall radiation shielding than the earth’s atmosphere.
    - idlewords 2y ago
      Total GCR dose is 3-5x in transit to Mars compared to what you get on ISS; on the Martian surface it's from 1.5-2x the ISS dose. (see https://www.swsc-journal.org/articles/swsc/pdf/2020/01/swsc200013.pdf https://www.swsc-journal.org/articles/swsc/pdf/2020/01/swsc2...). On a long-stay Mars mission, that adds up to 12-18 times the accumulated GCR exposure compared to a six-month ISS increment.
      - Robotbeat 2y ago
        Ah, you’re being tricky. You’re ignoring the substantial trapped radiation dose on ISS (it is, after all, the total dose that causes the defects). That, combined with GCR, gives an equivalent dose the same at Curiosity altitude as on ISS. In fact, look at Table 2. It shows that at ISS, the dose from the SAA is about the same as the GCR dose, so by ignoring trapped radiation, you’re manipulating the result by a factor of 2.

by Retric 2y ago

somenameforme 2y ago

No, NASA also didn't think it was possible at the time. There's an informative little paper here. [1] It only gets more informative from the first sentence, "Mathematical risk analysis was used in Apollo, but it gave unacceptably pessimistic results and was discontinued." By the time of the launch to the Moon NASA's internal estimates were looking at around a 50% chance of success based on Gene Krantz's (mission controller) "Failure is Not an Option" book. It was a mission they dedicated themselves to, and humans have this way of making things happen when we actually set our minds to tasks. A reality that's often been lost in modern times as we have mostly moved away from pursuing, let alone achieving, great things in the real world. One of the many reasons to get humans on Mars. [1] - https://ntrs.nasa.gov/api/citations/20190002249/downloads/20190002249.pdf https://ntrs.nasa.gov/api/citations/20190002249/downloads/20...

Retric 2y ago
You’re confusing specific low odds of success for “didn't think it was possible.” The Apollo missions got unbelievably lucky in that none catastrophically failed despite multiple close calls. However, if you’re willing to try multiple times the odds any mission being successful is much better than every mission being successful. IE: Six missions landed on the moon. If they each had independent 50% odds then six heads is a long way from impossible ~1.6%, but at least 1 head is quite likely ~98.4%. I doubt we would have tried for a 6th mission after 5 failures in a row, but the point is definitions of success matter a great deal here. Similarly failures improve odds of success in the future because you learn from mistakes and success means the system is functional eliminating some risks.
- somenameforme 2y ago
  What I'm demonstrating is that we indeed knew basically nothing. There was no secret tech or expectation of success. Mathematical models doomed the entire idea to failure, and all the way up to the day of the launch people who spent years in a bubble of optimism still didn't really expect more than a 50% chance of success.
  - Retric 2y ago
    > a 50% chance of success. On that specific launch, which is another way of saying they believed the project had a very good chance of having someone walking on the moon. Failure there wouldn’t even mean people died, just that they didn’t walk on the moon and then safely get back on that mission.
    - ANewFormation 2y ago
      That 50% was after years of bubble optimism and actively blinding themselves to data strongly suggestive otherwise. Had the Apollo missions failed you would obviously be arguing, using the exact same data, that they 'knew they never had a chance.'
      - Retric 2y ago
        > Had the Apollo missions failed you would obviously be arguing, using the exact same data, that they 'knew they never had a chance.' No, an earlier post argued that 6 successes doesn’t mean the odds of success on every mission was high. “Got unbelievably lucky” https://news.ycombinator.com/item?id=43130343 https://news.ycombinator.com/item?id=43130343 The exact opposite position after 6 failures would be that the odds were good that at least 1 mission would have succeeded. Obviously, things aren’t actually completely independent, but 6 lunar landings could have successfully been completed with a huge range of different odds. 50% odds of success on the first launch isn’t inconsistent with 6 successful launches or 6 failures, it’s just not enough data to really narrow things down.

Robotbeat 2y ago

On the contrary, we can easily get people there alive. What exactly do you think is beyond our capacity to send crew to Mars while still being alive? Crew regularly do year long expeditions on ISS (edited for clarity), with total radiation dose similar to Mars transit (and show no measurable effects of that radiation). Again, I’m addressing the point “getting them there alive”. Unquestionably, we know how to get crew to Mars alive, and even for the full mission duration, radiation isn’t even in the top 10 of the hazards that could actually kill them during the mission. (It’s a long term hazard, comparable to lung cancer if you’re a cigarette smoker.)

idlewords 2y ago
No one has ever done a "years long" expedition to ISS, and the radiation flux in transit to Mars, in particular GCR dose, is much higher than experienced on the space station.
- Robotbeat 2y ago
  I’m well aware, just mistyped. The total equivalent radiation dose on a fast transit to Mars is less than some ISS expeditions. Note that the magnetic field only deflects lower energy galactic cosmic rays which have a lower gyro radius than the real whoppers. The magnetic field is less important to overall radiation shielding than the earth’s atmosphere.
  - idlewords 2y ago
    Total GCR dose is 3-5x in transit to Mars compared to what you get on ISS; on the Martian surface it's from 1.5-2x the ISS dose. (see https://www.swsc-journal.org/articles/swsc/pdf/2020/01/swsc200013.pdf https://www.swsc-journal.org/articles/swsc/pdf/2020/01/swsc2...). On a long-stay Mars mission, that adds up to 12-18 times the accumulated GCR exposure compared to a six-month ISS increment.
    - Robotbeat 2y ago
      Ah, you’re being tricky. You’re ignoring the substantial trapped radiation dose on ISS (it is, after all, the total dose that causes the defects). That, combined with GCR, gives an equivalent dose the same at Curiosity altitude as on ISS. In fact, look at Table 2. It shows that at ISS, the dose from the SAA is about the same as the GCR dose, so by ignoring trapped radiation, you’re manipulating the result by a factor of 2.