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A JPL project manager teaching a course I took blamed it on the public's "mathematical illiteracy." He explained that there are diminishing returns on mission s

A JPL project manager teaching a course I took blamed it on the public's "mathematical illiteracy." He explained that there are diminishing returns on mission success rates so NASA often had the choice of paying X per mission attempt each with an 80% success rate or 2X for a single launch with 95% success rate. 80% sounds bad but the chance of two launches failing is 4%, which means a 96% chance overall success rate. If the first launch succeeds, they can usually save between 20-40% of the total budget (the remaining amount is overhead to build backups and keep scientists and engineers employed in case the first launch fails). However, since NASA is no longer doing world shattering stuff like landing on the moon, the human echo chamber amplifies each failure and drowns out the successes. Since NASA has to justify many appropriations on a per project basis, failures lead to projects getting canceled and NASA doing less actual science, even though their budget rarely shrinks - with more and more money instead allocated to inefficiencies like maintaining unused real estate/hardware and spreading out manufacturing across all districts in order to curry favor to get more projects going. That's just for robotic/satellite missions. It's ten times worse when a manned mission ends fatally.

jeffwass 7y ago
> since NASA is no longer doing world shattering stuff like landing on the moon NASA has its Artemis program which is doing exactly this, returning to the Moon with a goal of a longer-term lunar base. And they just held a period of application (it closed a few days ago) for the next generation of Artemis astronauts. Artemis : https://www.nasa.gov/specials/artemis/ https://www.nasa.gov/specials/artemis/
- nickik 7y ago
  Yeah they said they will return to the Moon or Mars (depending on the president) since Bush 1. That is almost 40 years. So another new moon plan. Another Shuttle derived launcher. Not surprising that nobody is getting very exited with Artemis. The SLS and Orion can only be described as dead-weights on NASA since they are so incredibly expensive. SLS has been in development for over 10 years at more then 2 billion per year and it will not launch until 2022 hopefully.
- rbanffy 7y ago
  > NASA has its Artemis program which is doing exactly this They've been designing Orion for a couple decades now, and the SLS is a shuttle-derived expendable launcher where what we see as key innovations are mounting 25% more SSMEs (still expendable) on the bottom of the fuel tank, extending the SRBs by a couple segments and putting the payload on top of the main tank. Ares was interesting and we learned, with Ares I, that we shouldn't put humans on top of an SRB. There would probably be cheaper ways to find that out, but at least they tried something different.
stdbrouw 7y ago
> 80% sounds bad but the chance of two launches failing is 4%, which means a 96% chance overall success rate. I don't disagree but I also don't think it's always as straightforward as probability theory would make us believe. One can imagine situations where a certain amount of QA leads to a certain semi-predictable amount of failures that allows for calculated risks to be taken, but one can also imagine situations where paying 2X leads to better solutions and processes and not paying 2X leads to failure on both the first and second launches.
nightcracker 7y ago
> 80% sounds bad but the chance of two launches failing is 4%, which means a 96% chance overall success rate I'm sorry, but this argument is also mathematically illiterate. Probability only works this way if the events are uncorrelated, but it should be pretty clear they're not. If the first rocket has a 20% chance to fail it is likely that the second one will also fail due to similar negligence.
- eru 7y ago
  It goes both ways. Perhaps they make the same mistakes, perhaps they'd learn from their mistakes, and would _not_ make the same ones?
- akiselev 7y ago
  You're right in theory but demonstrably wrong in reality. Just look at the failure rate of launch platforms in the last 30 years. If I remember correctly, launch failures accounted for less than half of mission failures and a significant number of those weren't explosions but burn rate problems that ended up in the wrong orbit. Rockets aren't mass manufactured and their fabrication is barely automated. Nobody except SpaceX keeps their tooling online long enough to have correlating failures except for actual design issues which are fixed in later launches. The correlated failure comes from the actual mission hardware but launch schedules are so spread out that a second mission has plenty of time to fix issues discovered in the first attempt. If rockets, which are made one at a time and launch maybe a few times a year, had correlating failures like you said, no insurance company would cover launches.

jeffwass 7y ago

> since NASA is no longer doing world shattering stuff like landing on the moon NASA has its Artemis program which is doing exactly this, returning to the Moon with a goal of a longer-term lunar base. And they just held a period of application (it closed a few days ago) for the next generation of Artemis astronauts. Artemis : https://www.nasa.gov/specials/artemis/ https://www.nasa.gov/specials/artemis/

nickik 7y ago
Yeah they said they will return to the Moon or Mars (depending on the president) since Bush 1. That is almost 40 years. So another new moon plan. Another Shuttle derived launcher. Not surprising that nobody is getting very exited with Artemis. The SLS and Orion can only be described as dead-weights on NASA since they are so incredibly expensive. SLS has been in development for over 10 years at more then 2 billion per year and it will not launch until 2022 hopefully.
rbanffy 7y ago
> NASA has its Artemis program which is doing exactly this They've been designing Orion for a couple decades now, and the SLS is a shuttle-derived expendable launcher where what we see as key innovations are mounting 25% more SSMEs (still expendable) on the bottom of the fuel tank, extending the SRBs by a couple segments and putting the payload on top of the main tank. Ares was interesting and we learned, with Ares I, that we shouldn't put humans on top of an SRB. There would probably be cheaper ways to find that out, but at least they tried something different.

stdbrouw 7y ago

> 80% sounds bad but the chance of two launches failing is 4%, which means a 96% chance overall success rate. I don't disagree but I also don't think it's always as straightforward as probability theory would make us believe. One can imagine situations where a certain amount of QA leads to a certain semi-predictable amount of failures that allows for calculated risks to be taken, but one can also imagine situations where paying 2X leads to better solutions and processes and not paying 2X leads to failure on both the first and second launches.

nightcracker 7y ago

> 80% sounds bad but the chance of two launches failing is 4%, which means a 96% chance overall success rate I'm sorry, but this argument is also mathematically illiterate. Probability only works this way if the events are uncorrelated, but it should be pretty clear they're not. If the first rocket has a 20% chance to fail it is likely that the second one will also fail due to similar negligence.

eru 7y ago
It goes both ways. Perhaps they make the same mistakes, perhaps they'd learn from their mistakes, and would _not_ make the same ones?
akiselev 7y ago
You're right in theory but demonstrably wrong in reality. Just look at the failure rate of launch platforms in the last 30 years. If I remember correctly, launch failures accounted for less than half of mission failures and a significant number of those weren't explosions but burn rate problems that ended up in the wrong orbit. Rockets aren't mass manufactured and their fabrication is barely automated. Nobody except SpaceX keeps their tooling online long enough to have correlating failures except for actual design issues which are fixed in later launches. The correlated failure comes from the actual mission hardware but launch schedules are so spread out that a second mission has plenty of time to fix issues discovered in the first attempt. If rockets, which are made one at a time and launch maybe a few times a year, had correlating failures like you said, no insurance company would cover launches.