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SpaceX NASA returning human spaceflight to United States today (canceled)

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Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#321

Post by bhhaskin »

orbital-decay wrote: post #95
mariushn wrote: post #46

Earlier quoted context omitted.

Is the touch screen usable during lift-off / landing? I'm thinking gravity (4+g?) and trepidations is making it hard to touch a specific spot. Or, maybe there isn't much to do manually during this phase, and for the little things there are some classic controls.

It's both. They have a handle below the screen precisely for this reason. [1] You can grab it and press the buttons below/tap the lower part of the screen above with your thumb. This seems much more reasonable and pragmatic than the sci-fi looking mockup they originally presented. [2] Although my understanding is that it's probably not a huge problem, because Soyuz introduced the stick to push the buttons only in its…

I would imagine they would have control lockouts as well. Not something super complicated/time consuming to disengage, but something to prefect that exact scenario from happening.

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#322

Post by bhhaskin »

luizfzs wrote: post #19
imshashank wrote: post #3

Love the new "Space" suits and the touch screen panel inside the capsule. This is going to be amazing. My prayers with the brave astronauts.

The space suit looks like it's made for a Halloween party. It looks kind of not flexible and fragile. The touch screen panel is surely very cool.

keep in mind that those aren't space suits, but flight suits.

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#323

Post by rkagerer »

mariushn wrote: post #46
imshashank wrote: post #3

Love the new "Space" suits and the touch screen panel inside the capsule. This is going to be amazing. My prayers with the brave astronauts.

Is the touch screen usable during lift-off / landing? I'm thinking gravity (4+g?) and trepidations is making it hard to touch a specific spot. Or, maybe there isn't much to do manually during this phase, and for the little things there are some classic controls.

https://www.reddit.com/r/spacex/comments/2floxq/are_there_co...

If I remember right, all the important controls are done with buttons and a joystick, while h touch screens are only for informational displays.

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#324

Post by derekp7 »

elliekelly wrote: post #290
jacquesm wrote: post #284

It looks like the launch will be scrubbed due to the weather, lightning risk during propellant loading is too high. edit: yep, launch scrubbed. Too bad! But better safe than sorry, especially today with a crewed vehicle. Does anybody know if the crew dragon comes with different weather restrictions for LOX loading?

Can someone ELI5 why they sometimes need to have an “instantaneous launch window” that can’t be pushed even by a few minutes?

To visualize one of the constraints (the orbit inclination) -- imagine holding up a hoop around a globe, with the hoop angled at 51.6 degrees. Now start spinning the globe until Florida intersects with the hoop. That is when it has to launch, to be going in the same direction as that hoop.

Spin the globe a bit further, and now you can see that Florida no longer intersects with that hoop. If you were to try to launch at that point, your trajectory would form another ring that intersects with the ISS's orbit, but at a different angle. So it would take quite a bit more propellant to change direction once in space.

Now, you also have to launch so that you intercept the ISS when it is at the proper position on that hoop. If, when you reach the hoop the ISS is half way around the world, you won't get to it. (Technically, you can spend some time at a lower orbit, then raise your orbit at the right time, or adjust the amount of time it takes to get to the right height, but again that messes with the timing of everything and fuel usage).

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#325

Post by TheOtherHobbes »

NikolaeVarius wrote: post #303
elliekelly wrote: post #290

Earlier quoted context omitted.

Can someone ELI5 why they sometimes need to have an “instantaneous launch window” that can’t be pushed even by a few minutes?

Long list but one of the big ones: ISS travels at 7.6 km/s. Thats a lot of kms in those few minutes

Around 17,000mph.

A miss is much bigger than a mile.

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#326

Post by orbital-decay »

bhhaskin wrote: post #321
orbital-decay wrote: post #95

Earlier quoted context omitted.

It's both. They have a handle below the screen precisely for this reason. [1] You can grab it and press the buttons below/tap the lower part of the screen above with your thumb. This seems much more reasonable and pragmatic than the sci-fi looking mockup they originally presented. [2] Although my understanding is that it's probably not a huge problem, because Soyuz introduced the stick to push the buttons only in its…

I would imagine they would have control lockouts as well. Not something super complicated/time consuming to disengage, but something to prefect that exact scenario from happening.

Yes, the lockouts were in place during that incident too, but for several good reasons they are non-modal - you have to hold two buttons at the same time to trigger some critical operations like manual RCS controls. Which is exactly what happened, so the confirmation procedure had to be changed as well.

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#327

Post by m4rtink »

gpm wrote: post #316
jacquesm wrote: post #306

Earlier quoted context omitted.

So is that lightning strike concern limited to the second stage?

I believe that the lightning strike concern is lightning strikes during flight not on the ground. They've got plenty of lightning towards around the rocket on the ground, and if it would be useful they could have easily added more taller ones. They just don't want to load the propellant if there is no chance of launching.

IIRC the exhaust trail aftera a rocket is actually ionised and efectively grounds the rocket in flight, creating a giant lightnjng rod. This was discovered during the Apollo 12 launch and caused serious but thankfulyy not fatal issues. Since then people are rather careful about preventing launches if lightning danger around the launch area is too high.

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#328

Post by jamesmontalvo3 »

dmurray wrote: post #312
lutorm wrote: post #304

Earlier quoted context omitted.

It depends on the target orbit. For launches to the ISS, you have to launch at the correct instant because even a few minutes later means the ISS is so far ahead it will take much longer, and use more propellant, to rendezvous. I think they could probably delay a few seconds without too much trouble, but I guess the extra complication of recalculating the rendezvous isn't worth it because most of the time a few secon…

Can you delay the launch window 90 minutes until the next ISS orbit? Maybe you then run into the next on the long list of reasons.

In 90 minutes the space station is back at the same point in its orbit, but Kennedy Space Center has rotated ~1500 miles east.

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#329

Post by DuskStar »

derekp7 wrote: post #324
elliekelly wrote: post #290

Earlier quoted context omitted.

Can someone ELI5 why they sometimes need to have an “instantaneous launch window” that can’t be pushed even by a few minutes?

To visualize one of the constraints (the orbit inclination) -- imagine holding up a hoop around a globe, with the hoop angled at 51.6 degrees. Now start spinning the globe until Florida intersects with the hoop. That is when it has to launch, to be going in the same direction as that hoop. Spin the globe a bit further, and now you can see that Florida no longer intersects with that hoop. If you were to try to launch…

> Now, you also have to launch so that you intercept the ISS when it is at the proper position on that hoop. If, when you reach the hoop the ISS is half way around the world, you won't get to it. (Technically, you can spend some time at a lower orbit, then raise your orbit at the right time, or adjust the amount of time it takes to get to the right height, but again that messes with the timing of everything and fuel usage).

This is normal, actually. It's part of why it normally takes several days from launch to ISS rendezvous. (Another part is that the trajectory is very carefully calculated to not leave the spacecraft on an intercept course with the ISS if anything breaks) And it takes essentially no fuel - 100m/s of closing rate will let you catch up from halfway around the world in 2-3 days.

Re: SpaceX NASA returning human spaceflight to United States today (canceled)

#330

Post by kempbellt »

DuskStar wrote: post #329
derekp7 wrote: post #324

Earlier quoted context omitted.

To visualize one of the constraints (the orbit inclination) -- imagine holding up a hoop around a globe, with the hoop angled at 51.6 degrees. Now start spinning the globe until Florida intersects with the hoop. That is when it has to launch, to be going in the same direction as that hoop. Spin the globe a bit further, and now you can see that Florida no longer intersects with that hoop. If you were to try to launch…

> Now, you also have to launch so that you intercept the ISS when it is at the proper position on that hoop. If, when you reach the hoop the ISS is half way around the world, you won't get to it. (Technically, you can spend some time at a lower orbit, then raise your orbit at the right time, or adjust the amount of time it takes to get to the right height, but again that messes with the timing of everything and fuel…

This makes sense. If you aren't in a huge rush to reach your destination and can spend 2-3 days to let your orbit match the ISS. If launch windows were weeks or months apart, a couple days of catch-up orbiting might be okay.

Though, if you can spend that same amount of time sitting on the ground and get there at roughly the same time, you'd waste less resources sustaining the crew in orbit, as well as reducing the "Ugh, are we there yet??" factor by a decent amount.

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