5 ms·

Richard P. Feynman's reports

76 points by Aarvay 15y ago

thirsteh 15y ago
"Only realistic flight schedules should be proposed—schedules that have a reasonable chance of being met. If in this way the government would not support NASA, then so be it. NASA owes it to the citizens from whom it asks support to be frank, honest, and informative, so that these citizens can make the wisest decisions for the use of their limited resources. For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." Great guy. Also: http://www.haveabit.com/feynman/14002 http://www.haveabit.com/feynman/14002
- Aarvay 15y ago
  He's the most influential person!
  - cema 15y ago
    Influential on scientists and engineers. Not sufficiently influential on bureaucrats and managers.
- spitfire 15y ago
  Also neat in that video is Daniel Hills and the connection machine.
pdx 15y ago
There is not enough room in the memory of the main line computers for all the programs of ascent, descent, and payload programs in flight, so the memory is loaded about four time from tapes, by the astronauts.
PaulHoule 15y ago
The official predicated catastrophic failure rate for the Shuttle has been about 3% per launch from the time that the design was finalized. Various upgrades to improve safety haven't changed this number, since the "unknown unknowns" the dominant failure mode. This failure rate, of course, was close to what we observed in experience. What's funny about this is they were planning about 50 launches a year at the beginning, which, if they believed their own numbers, would have mean the loss of a vehicle and crew every year, and the complete destruction (or replacement?) of the Shuttle fleet on the time scale of five years or so. The first failure (much like Three Mile Island) could be dismissed as a fluke, a problem which could be fixed. The second failure (like Fukushima) represented a typical failur e mode -- there was a lot of hand-wringing over the ceramic tiles on the first few shuttle flights, and after a few flights without a disaster, NASA assumed there was nothing to worry about, and that was wrong. The shuttle program was ended because there's no way to make the ceramic tiles safe. Now, Fukushima is an extreme case of a failure -- it was probably the worst built nuclear power plant in the most dangerous location, but it represents the most likely LWR failure mode: not a stuck valve or simple operator error, but a major catastrophe that prevents cooling of the core and spent fuel. Unlike the shuttle, we can make that a lot less likely.
- celoyd 15y ago
  it was probably the worst built nuclear power plant in the most dangerous location I was going to dispute this based on things I’ve heard about Russian reactor operations, but apparently they’re generally placed well away from natural hazards. Since you seem to pay attention to the issue, which do you consider the riskiest reactors now?
  - PaulHoule 15y ago
    I don't like the CANDU reactors from Canada. It's really quite an accomplishment that Canada's developed an exportable technology, but they aren't as safe as the LWR reactors that most countries use. One problem is that the piping is much more complicated than other reactors, so the possibility of springing a leak is much higher. CANDU reactors also have a positive void reactivity coefficient, which means that they're much more dependent on electronics to prevent power excursions. They also produce and leak tritium at a much higher rate -- it's not clear that this is a real problem, but it's very detectable. The economics of running on natural uranium aren't so good now that gas centrifuges can refine uranium more efficiently than the old gas diffusion plants. Nobody will argue that a CANDU reactor properly operated will produce weapons-grade plutonium, but a country that's able to build CANDU reactors domestically could construct CANDU derivatives which would be useful for proliferation. I wouldn't say that BWR reactors are categorically unsafe, but looking at the operating history, I think PWR reactors have a better record, even leaving Fukushima out. I don't know if BWR reactors or derivatives like the ESBWR have a future at this point. The Mark I BWR at the Fukushima site lacked many of the safety upgrades that have been made at other countries... Regulators in the US were aware of the problem that blew the roof off several of the reactors in the 1980s and took steps to prevent that step in the accident progression -- and don't kid yourself it wasn't significant, because a collapsed building is a dangerous environment that makes it hard to work around the reactor, particularly when you want to get in and get out fast to minimize your radiation dose. I'd really like to see small PWR reactors with natural convection like mPower from B&W and the NuScale reactor. I think these can be very safe and also, being factory constructed, control the cost escalation that scares utilities away from investing in nuclear. I'd also like to see a realistic plan for fuel management -- we don't know the whole story at Fukushima yet, but spent fuel was part of the problem, and having a plan that's better than stacking it up at reactor sites is important.
deleted 15y ago
[deleted]
boredguy8 15y ago
There are perpetual requests for changes as new payloads and new demands and modifications are suggested by the users. Changes are expensive because they require extensive testing. The proper way to save money is to curtail the number of requested changes, not the quality of testing for each. Preach it.
- pjscott 15y ago
  Streamlining the testing process is also a good option.
keithpeter 15y ago
"When playing Russian roulette the fact that the first shot got off safely is little comfort for the next." Love the quote, and something to bear in mind when evaluating less drastic forms of hazard. Anyone care to comment on Tufte's take on the graphics used by the Thiokol engineers? See http://www.asktog.com/books/challengerExerpt.html http://www.asktog.com/books/challengerExerpt.html
andrewljohnson 15y ago
It must have been great to be the software team when this report hit. It's the only part of the engineering Feynman thinks is really good: "To summarize then, the computer software checking system and attitude is of the highest quality." And this is a good example of Conway's Law too, that software grows to resemble its organization. You can imagine that the software team at NASA during this time was the very bleeding edge of software - it was a somewhat new field, and they were doing the most dangerous stuff. I bet they recruited bright people, and those people's only assumption was that failure was not an option. They were probably used to their software failing all the time - they planend for the worst, and expected the worst, and had no preconceptions about their own abilities. Compare that to the hardware side of things, probably filled with old-school aviation engineers who had been around the world a few times. The managers making the 1 in 100 calculations were probably hardware guys in the past too, because there weren't too many 45 year old programmers when this report came out. And so they go in, with experience that says airplanes don't crash very much, and a space shuttle is just a big airplane. Cue the bureaucrats with their deadlines and budgets, and mix that with the arrogance of once-technical aviation engineer managers, and a 3% failure rate still sounds pretty rosy.

76 points by Aarvay 15y ago

"Only realistic flight schedules should be proposed—schedules that have a reasonable chance of being met. If in this way the government would not support NASA, then so be it. NASA owes it to the citizens from whom it asks support to be frank, honest, and informative, so that these citizens can make the wisest decisions for the use of their limited resources. For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." Great guy. Also: http://www.haveabit.com/feynman/14002 http://www.haveabit.com/feynman/14002

Aarvay 15y ago
He's the most influential person!
- cema 15y ago
  Influential on scientists and engineers. Not sufficiently influential on bureaucrats and managers.
spitfire 15y ago
Also neat in that video is Daniel Hills and the connection machine.

pdx 15y ago

There is not enough room in the memory of the main line computers for all the programs of ascent, descent, and payload programs in flight, so the memory is loaded about four time from tapes, by the astronauts.

PaulHoule 15y ago

The official predicated catastrophic failure rate for the Shuttle has been about 3% per launch from the time that the design was finalized. Various upgrades to improve safety haven't changed this number, since the "unknown unknowns" the dominant failure mode. This failure rate, of course, was close to what we observed in experience. What's funny about this is they were planning about 50 launches a year at the beginning, which, if they believed their own numbers, would have mean the loss of a vehicle and crew every year, and the complete destruction (or replacement?) of the Shuttle fleet on the time scale of five years or so. The first failure (much like Three Mile Island) could be dismissed as a fluke, a problem which could be fixed. The second failure (like Fukushima) represented a typical failur e mode -- there was a lot of hand-wringing over the ceramic tiles on the first few shuttle flights, and after a few flights without a disaster, NASA assumed there was nothing to worry about, and that was wrong. The shuttle program was ended because there's no way to make the ceramic tiles safe. Now, Fukushima is an extreme case of a failure -- it was probably the worst built nuclear power plant in the most dangerous location, but it represents the most likely LWR failure mode: not a stuck valve or simple operator error, but a major catastrophe that prevents cooling of the core and spent fuel. Unlike the shuttle, we can make that a lot less likely.

celoyd 15y ago
it was probably the worst built nuclear power plant in the most dangerous location I was going to dispute this based on things I’ve heard about Russian reactor operations, but apparently they’re generally placed well away from natural hazards. Since you seem to pay attention to the issue, which do you consider the riskiest reactors now?
- PaulHoule 15y ago
  I don't like the CANDU reactors from Canada. It's really quite an accomplishment that Canada's developed an exportable technology, but they aren't as safe as the LWR reactors that most countries use. One problem is that the piping is much more complicated than other reactors, so the possibility of springing a leak is much higher. CANDU reactors also have a positive void reactivity coefficient, which means that they're much more dependent on electronics to prevent power excursions. They also produce and leak tritium at a much higher rate -- it's not clear that this is a real problem, but it's very detectable. The economics of running on natural uranium aren't so good now that gas centrifuges can refine uranium more efficiently than the old gas diffusion plants. Nobody will argue that a CANDU reactor properly operated will produce weapons-grade plutonium, but a country that's able to build CANDU reactors domestically could construct CANDU derivatives which would be useful for proliferation. I wouldn't say that BWR reactors are categorically unsafe, but looking at the operating history, I think PWR reactors have a better record, even leaving Fukushima out. I don't know if BWR reactors or derivatives like the ESBWR have a future at this point. The Mark I BWR at the Fukushima site lacked many of the safety upgrades that have been made at other countries... Regulators in the US were aware of the problem that blew the roof off several of the reactors in the 1980s and took steps to prevent that step in the accident progression -- and don't kid yourself it wasn't significant, because a collapsed building is a dangerous environment that makes it hard to work around the reactor, particularly when you want to get in and get out fast to minimize your radiation dose. I'd really like to see small PWR reactors with natural convection like mPower from B&W and the NuScale reactor. I think these can be very safe and also, being factory constructed, control the cost escalation that scares utilities away from investing in nuclear. I'd also like to see a realistic plan for fuel management -- we don't know the whole story at Fukushima yet, but spent fuel was part of the problem, and having a plan that's better than stacking it up at reactor sites is important.

deleted 15y ago

[deleted]

boredguy8 15y ago

There are perpetual requests for changes as new payloads and new demands and modifications are suggested by the users. Changes are expensive because they require extensive testing. The proper way to save money is to curtail the number of requested changes, not the quality of testing for each. Preach it.

pjscott 15y ago
Streamlining the testing process is also a good option.

keithpeter 15y ago

"When playing Russian roulette the fact that the first shot got off safely is little comfort for the next." Love the quote, and something to bear in mind when evaluating less drastic forms of hazard. Anyone care to comment on Tufte's take on the graphics used by the Thiokol engineers? See http://www.asktog.com/books/challengerExerpt.html http://www.asktog.com/books/challengerExerpt.html

andrewljohnson 15y ago

It must have been great to be the software team when this report hit. It's the only part of the engineering Feynman thinks is really good: "To summarize then, the computer software checking system and attitude is of the highest quality." And this is a good example of Conway's Law too, that software grows to resemble its organization. You can imagine that the software team at NASA during this time was the very bleeding edge of software - it was a somewhat new field, and they were doing the most dangerous stuff. I bet they recruited bright people, and those people's only assumption was that failure was not an option. They were probably used to their software failing all the time - they planend for the worst, and expected the worst, and had no preconceptions about their own abilities. Compare that to the hardware side of things, probably filled with old-school aviation engineers who had been around the world a few times. The managers making the 1 in 100 calculations were probably hardware guys in the past too, because there weren't too many 45 year old programmers when this report came out. And so they go in, with experience that says airplanes don't crash very much, and a space shuttle is just a big airplane. Cue the bureaucrats with their deadlines and budgets, and mix that with the arrogance of once-technical aviation engineer managers, and a 3% failure rate still sounds pretty rosy.