3 ms·

IMHO the number of flights seems like a much more important metric of durability, since virtually all the stress will be imposed on the frame during launch and

IMHO the number of flights seems like a much more important metric of durability, since virtually all the stress will be imposed on the frame during launch and reentry. It doesn't make a huge difference if you spent 8 or 180 days docked to the ISS in between.

bruce511 3y ago
It kinda does though. The ISS orbits every 90 minutes or so. Meaning it cycles from very-hot to very-cold. Doing that for 180 days means thousands of cycles. While not as violent as take-off and landing, it's a factor that can lead to metal fatigue and so on. Quite how big a factor remains to be seen, hence the fairly strong observance, and testing of parts (earthside) after they return.
- rbanffy 3y ago
  I wonder if a deployable sunshade would help extending their life. When Skylab lost one solar panel array on launch, they had to cover it with a blanket to help manage temperatures.
- EnigmaFlare 3y ago
  If that's what's important then the ISS itself has beaten it. So it still seems like an arbitrarily narrowly chosen record just to make it seem special by limiting it to transport spacecraft. Everything beats some sort of record if you exclude enough others.
Octoth0rpe 3y ago
launch/reentry are of course huge stressors, but IIRC just being docked subjects a spacecraft to a larger temperature range than you might expect. From NASA: > Without thermal controls, the temperature of the orbiting Space Station's Sun-facing side would soar to 250 degrees F (121 C), while thermometers on the dark side would plunge to minus 250 degrees F (-157 C). That's a lot of thermal expansion/contraction, every 90 minutes. I'm not sure if that actually adds up to being equivalent to the much larger # of launches/reentries that discovery underwent, but it's _something_.
dotnet00 3y ago
That has its own issues as a metric, since the Shuttles were much more fragile and had to go through much more refurbishment compared to Dragon.

bruce511 3y ago

It kinda does though. The ISS orbits every 90 minutes or so. Meaning it cycles from very-hot to very-cold. Doing that for 180 days means thousands of cycles. While not as violent as take-off and landing, it's a factor that can lead to metal fatigue and so on. Quite how big a factor remains to be seen, hence the fairly strong observance, and testing of parts (earthside) after they return.

rbanffy 3y ago
I wonder if a deployable sunshade would help extending their life. When Skylab lost one solar panel array on launch, they had to cover it with a blanket to help manage temperatures.
EnigmaFlare 3y ago
If that's what's important then the ISS itself has beaten it. So it still seems like an arbitrarily narrowly chosen record just to make it seem special by limiting it to transport spacecraft. Everything beats some sort of record if you exclude enough others.

Octoth0rpe 3y ago

launch/reentry are of course huge stressors, but IIRC just being docked subjects a spacecraft to a larger temperature range than you might expect. From NASA: > Without thermal controls, the temperature of the orbiting Space Station's Sun-facing side would soar to 250 degrees F (121 C), while thermometers on the dark side would plunge to minus 250 degrees F (-157 C). That's a lot of thermal expansion/contraction, every 90 minutes. I'm not sure if that actually adds up to being equivalent to the much larger # of launches/reentries that discovery underwent, but it's _something_.

dotnet00 3y ago

That has its own issues as a metric, since the Shuttles were much more fragile and had to go through much more refurbishment compared to Dragon.