[Starlink] saving ship 20

[David Lang]

On Sat, 12 Feb 2022, Dave Taht wrote:

> Having a pause to inspect the lost tiles, and assess the damage before
> even attempting re-entry strikes me as a good idea. I hope they've
> lined up some good telescopes this time to take a peek at it. Always
> sad we didn't get that done for columbia.

for this first flight, they are deliberatly not going into an orbit that would 
clear the ground (they are going high enough, and fast enough, but not round 
enough), so that they don't need to deal with the complications of a zero-g 
restart (settling the fuel, etc)

They have lined up the NASA aircraft that has a big telescope on it to watch it 
during reentry, and unlike everyone else, they put lots of cameras on and in 
their rockets (spectacular PR and very useful to figure out what went wrong)

Odds are that something will go wrong before reentry on the first flight, but 
they have the timeline go all the way to a landing burn above the ocean, but I 
don't think anyone is expecting it to be intact by the time it spashes down. It 
would be an absolutly spectacular win if it does survive to that point.

> Developing the capability to do on-orbit repair, also is a good goal.
>
> A small robot to do external inspection?
>
> It seems pointless to attempt re-entry if you determined it was going to
> fail and seems better to plan on exploring other options.

until we have a lot more access to space, people are more afraid of 'space junk' 
than interested in accumulating resources in space.

Even if they end up missing some tiles and get a burn-through during reentry, 
it's worth doing the reentry to learn how the skydiver approach works compared 
to what every other spacecraft has done. There has never been anything close to 
this big that's attempted reentry, they don't know how well the computer models 
actually match reality. Given that it will be years before there is manned 
flight that would be able to use it if they left it up there, odds are good that 
it would come down first anyway, just in an uncontrolled fashion.

I'll point out that the bigelow inflatable module on the ISS is only being used 
for storage, NASA doesn't trust inflatables.

>>
>> And, as we have seen many times, getting back in one piece is the hardest
>> part to get right.
>
> So why not have a plan B involving staying in orbit, rather than burning up?

if you never attempt reentry, you can never succeed.

>>
>> > Do they not have enough thrust, even with an empty payload bay, to
>> > stay up there?
>>
>> I'm sure they do, but to stay up they would need a course corrction
>> or two.
>
> testing restart seems smart.

these are gen-1 raptor engines, given how much more complicated they are than 
the gen-2 raptors, how useful would it be? and it would add a LOT of 
complication. Also, unless you boosted it up above the ISS, it will deorbit 
fairly quickly. Starlinks are higher and denser, and they have a lifetime of 5 
years or so without reboost.

David Lang