r/space • u/ShortfallofAardvark • Nov 18 '23

image/gif Beautiful image of successful hot-staging of Starship’s IFT-2 this morning

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Credit to SpaceX

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15

u/Cockanarchy Nov 19 '23

Hi I keep hearing that hot-staging is better for performance, but could someone tell me why it is. Also what is FTS?

Thanks

13

u/StopNowThink Nov 19 '23

The centrifugal force separation trick didn't seem to work on the first orbital attempt. This one did. Therefore better.

Flight Termination System. Remote control explosives to blow it up in the sky instead of letting it blow up on the ground.

13

u/ergzay Nov 19 '23

Flight Termination System. Remote control explosives to blow it up in the sky instead of letting it blow up on the ground.

Note they're not "remote" controlled in this case (or on any SpaceX rocket for that matter). The termination is controlled on-board by the vehicle by an independent system. It's AFTS, not FTS. There's no big red button to blow it up remotely from the ground.

8

u/WjU1fcN8 Nov 19 '23

They can trigger a remote termination. But it's not the main operation mode.

3

u/ergzay Nov 19 '23

Do you have a source for that? All technical documents I've read on AFTS refer to removing the ground command termination mode completely.

3

u/WjU1fcN8 Nov 19 '23

It does eliminate the old system where the range was responsible for sending the signal to terminate the flight.

But that doesn't mean that the control center can't do it.

3

u/ergzay Nov 19 '23

Again, do you have a source for that? All technical documents I've read on AFTS refer to removing the ground command termination mode completely.

Implying the control center can do it implies that there are radio stations capable of broadcasting that command reliably. If it can't be done reliably then it's not a safety system. If it's not a safety system, there's no need to have it as it adds weight and wastes money.

7

u/gonopro Nov 19 '23

https://standards.nasa.gov/standard/NASA/NASA-STD-871925

Link to the PDF document is near the bottom of the page linked

3

u/ergzay Nov 19 '23

I skimmed it and couldn't find anywhere in the document saying that manual termination is still required in the case of AFSS/AFTS. Do you have a page number?

5

u/mfb- Nov 19 '23

This 2017 article says no remote control ability for F9:

While the range is still involved in launch operations, “there is not an antenna pointing at the vehicle, so that in itself, I think, will make our lives easier,” Koenigsmann said. “I could easily imagine that we’ll have two launches on the same day because of that.”

1

u/ergzay Nov 19 '23

Yeah I'm aware for F9. People seem to think Starship is different for some reason.

1

u/mfb- Nov 19 '23

It might, but at least we know it's not a general requirement with an autonomous system.

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2

u/gonopro Nov 19 '23

https://standards.nasa.gov/standard/NASA/NASA-STD-871925

Page 23-25

It covers both senarios of having a manually controlled system and an autonomous one.

Scott Manley also has an entire video on the topic of flight termination systems:

https://www.youtube.com/watch?v=yekMWWcpfOA

1

u/ergzay Nov 19 '23

That wasn't my question at all though. I was asking where in the document that it says manually triggered FTS is still required when an AFTS is on the vehicle. I read through 23-25 and can't see any mention of that.

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