101–110 of 159 posts
I discovered this when my father would come up with some project me and my siblings had to do, such as scrape, sand, prime and paint the house (which thinking back very likely had lead paint).
It would inevitably take roughly 3 times longer than he wanted it to take. And of course being an adult he'd throw a tantrum about it.
Virgil wrote the Aeneid by following this rule!
>29. (von Tiesenhausen's Law of Program Management) To get an accurate estimate of final program requirements, multiply the initial time estimates by pi... I discovered this when my father would come up with some project me and my siblings had to do, such as scrape, sand, prime and paint the house (which thinking back very likely had lead paint). It would inevitably take roughly 3 times longer than he wanted it to ta…
I’m not sure the early Apollo astronauts would agree.
Number 13. Design is based on requirements. There's no justification for designing something one bit "better" than the requirements dictate. Isn't that the margin for error? I want to go up in a ship that's a little better than the absolute minimum.
Good requirements include margins. In aerospace it's common to see[1] a system requirement that says "...shall supply a peak current of 1.0A for 1.0s", a general requirement somewhere else that says "...power supplies used for the purpose of X shall be designed to a margin of 1.5 for current and a margin of 2.0 for time", and a child of both that says "...shall supply a peak current of 1.5A for 2.0s, including margin…
I’m kidding…
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A decade is a short period of time by human-rated-spaceflight standards.
So? Falcon wasn't a human spaceflight program during that time, and it was also over-schedule and over-budget anyway. The advice isn't "no new launch vehicles should ever be invented ever", it's "if you want your human spaceflight program to be on time and on budget, don't include a new launch vehicle in the plan"
And that advice is being questioned. Starship aims at cost reduction which can't reasonably be achieved by incremental improvements to the status quo.
The "on time" part with Starship is what was formally promised to NASA with the Moon landing vehicle. This may - probably will - slip, but I currently doubt it will slip a lot. Other times regarding Starship are in the realm of estimates or wishful statements. The "on budget" part is something which I doubt even SpaceX accountants may answer - just as software engineers have troubles answering the time - and therefore budget - of a system to be delivered.
The law shows its age. On the other hand, it never claimed to be an absolute truth.
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I'd consider development of Crew Dragon to be rather fast - because, in the condition of a private development, it wasn't done before. Comparing to other spacecraft developments, in late 1950-s there was a race, USA vs. USSR, to put a man in space "soonest", and it took Soviets ~3.5 years from the launch of the Sputnik to send Gagarin to orbit. So, just a few short years... and a large government backing. Still, give…
Compare the budget of SpaceX to NASA's up to and through Mercury. NASA's experience was one of something never having been done before compared to the experience of SpaceX seeing many others doing it just needing to tweak the formula to make it affordable. Also, without NASA's burden of being a government pork/jobs program rather than being a streamlined process
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Late comparing to what? Maybe SpaceX will not make it ready for NASA's return to the Moon flights as it was planned. However those dates don't look too serious to me - what's the justification for them? I suspect they were specified fully understanding they can easily slip right. Over-budget - what's the planned budget? I suspect Elon Musk himself doesn't have pre-approved specific budget to develop Starship, which m…
So, it's not late because the dates weren't serious to begin with?
> Design is based on requirements. There's no justification for designing something one bit "better" than the requirements dictate. I’m not sure the early Apollo astronauts would agree.