SpaceX (Vol. 2)

[Hill92]

Caruso said:

Beati Dogu said:

Well that was fun and double landings will always be cool.


Unrelated, but interesting nonetheless: NASA have awarded SpaceX a ~$850 million contract to deorbit the ISS after it is retired in 2030.

https://www.nasa.gov/news-release/nasa-selects-int...

Interesting I wonder what hardware they will develop for that and how it will be done I.e. in sections or as a whole?

Early expectations seem to be for an adapted Cargo Dragon using the Draco engines. SuperDraco on Crew Dragon is considered too powerful. It also appears that the whole structure is expected to be deorbited in one piece.

NASA did give consideration to dismantling ISS and returning it to Earth. But even using Starship it would take as many spacewalks to dismantle as it did to construct it, if not more as it was never designed to be dismantled.

NASA are looking to commercial space stations by 2030. Axiom intend to launch their first compartment in 2026.

[LivLL]

May sound completely stupid but as a layman would it be possible to gently thrust it out of Earth orbit and position is somewhere so that it remains forever ( bit like the Tesla Roadster in space ). Seems a shame to just burn it up in the atmosphere

[Hill92]

LivLL said:

May sound completely stupid but as a layman would it be possible to gently thrust it out of Earth orbit and position is somewhere so that it remains forever ( bit like the Tesla Roadster in space ). Seems a shame to just burn it up in the atmosphere

Not really. Although they do regular reboosts to counter sinking from atmospheric drag, there are doubts the structure would be strong enough to withstand the necessary delta V to significantly change orbit. Higher orbits also pose greater space debris risks. But most of all it needs humans on board to keep patching it up. Hence parking it in a higher orbit was discounted.

[CraigyMc]

Hill92 said:

LivLL said:

May sound completely stupid but as a layman would it be possible to gently thrust it out of Earth orbit and position is somewhere so that it remains forever ( bit like the Tesla Roadster in space ). Seems a shame to just burn it up in the atmosphere

Not really. Although they do regular reboosts to counter sinking from atmospheric drag, there are doubts the structure would be strong enough to withstand the necessary delta V to significantly change orbit. Higher orbits also pose greater space debris risks. But most of all it needs humans on board to keep patching it up. Hence parking it in a higher orbit was discounted.

I think the total amount of delta-V to add is relatively unimportant compared with the speed with which it is added. With a large amount of propellant and a relatively small thruster/rocket, you could add the required velocity over a long period of time. Ultimately it's probably possible to chuck the ISS out of earth orbit, given enough time, and staying within the structural limits of the structure.

Why do it is more of a blocker.

[Solocle]

Hill92 said:

LivLL said:

May sound completely stupid but as a layman would it be possible to gently thrust it out of Earth orbit and position is somewhere so that it remains forever ( bit like the Tesla Roadster in space ). Seems a shame to just burn it up in the atmosphere

Not really. Although they do regular reboosts to counter sinking from atmospheric drag, there are doubts the structure would be strong enough to withstand the necessary delta V to significantly change orbit. Higher orbits also pose greater space debris risks. But most of all it needs humans on board to keep patching it up. Hence parking it in a higher orbit was discounted.

Yep, and if you bump it up to Earth escape velocity it ends up on a heliocentric orbit that will eventually encounter the Earth again. e.g. an NEO J002E3, which was found orbiting Earth in 2002 (and anything orbiting that high will quickly be ejected by the Moon, so it has recently been captured).

Plotting its orbit back, it turned out it had last been in the vicinity of the Earth in 1971. It's now generally thought to be the S-IVB third stage of Apollo 12.

Now, if there's any hardware that deserves recovery, lunar orbits tend to be unstable, however modelling indicates that Eagle might still be orbiting the Moon and not crashed into its surface (yet).

[Talksteer]

Hill92 said:

LivLL said:

May sound completely stupid but as a layman would it be possible to gently thrust it out of Earth orbit and position is somewhere so that it remains forever ( bit like the Tesla Roadster in space ). Seems a shame to just burn it up in the atmosphere

Not really. Although they do regular reboosts to counter sinking from atmospheric drag, there are doubts the structure would be strong enough to withstand the necessary delta V to significantly change orbit. Higher orbits also pose greater space debris risks. But most of all it needs humans on board to keep patching it up. Hence parking it in a higher orbit was discounted.

I suspect that due to the way bureaucracy works the capabilities of Starship wasn't really considered when drafting the spec. The other suggestion around this is that the tug is also a back-up in case they have to jettison the Russian bits or they break this can do re-boosting and attitude control.

Doing some very basic maths a ~50 tonne electric propulsion device could get the ISS to a graveyard beyond GEO, something in the order of a fully fueled Starship could also get it there. With a caveat that it would probably need to a depot craft as the thrust that the ISS can take is 222N, this would mean that a Methane rocket would be burning for about 30 days in total (actually it would be higher as this would be a low thrust trajectory so more delta v is needed).

I suspect that a graveyard orbit doesn't need to be all the way to GEO as relatively few things pass through a MEO orbit and they tend to be in control when they do.

Suspicion is that we won't deorbit the ISS and that rapidly evolving technology will make a parking orbit feasible and possibly people like Musk and Bezos might be up for funding it even if the US Government isn't interested. I presume that Starship or similar will also likely bring the Hubble Space Telescope back either that or bring it to a "Space Museum".

[CraigyMc]

Talksteer said:

Hill92 said:

LivLL said:

May sound completely stupid but as a layman would it be possible to gently thrust it out of Earth orbit and position is somewhere so that it remains forever ( bit like the Tesla Roadster in space ). Seems a shame to just burn it up in the atmosphere

Not really. Although they do regular reboosts to counter sinking from atmospheric drag, there are doubts the structure would be strong enough to withstand the necessary delta V to significantly change orbit. Higher orbits also pose greater space debris risks. But most of all it needs humans on board to keep patching it up. Hence parking it in a higher orbit was discounted.

I suspect that due to the way bureaucracy works the capabilities of Starship wasn't really considered when drafting the spec. The other suggestion around this is that the tug is also a back-up in case they have to jettison the Russian bits or they break this can do re-boosting and attitude control.

Doing some very basic maths a ~50 tonne electric propulsion device could get the ISS to a graveyard beyond GEO, something in the order of a fully fueled Starship could also get it there. With a caveat that it would probably need to a depot craft as the thrust that the ISS can take is 222N, this would mean that a Methane rocket would be burning for about 30 days in total (actually it would be higher as this would be a low thrust trajectory so more delta v is needed).

I suspect that a graveyard orbit doesn't need to be all the way to GEO as relatively few things pass through a MEO orbit and they tend to be in control when they do.

Suspicion is that we won't deorbit the ISS and that rapidly evolving technology will make a parking orbit feasible and possibly people like Musk and Bezos might be up for funding it even if the US Government isn't interested. I presume that Starship or similar will also likely bring the Hubble Space Telescope back either that or bring it to a "Space Museum".

Interesting point on starship bringing stuff back. Obviously at the moment it's marginal even bringing its own mass back, imagine that plus 12 tons, plus the extra fuel required to hover with 12t of mass on board.

I don't think returning anything is currently in their design spec. Maybe eventually.

[Beati Dogu]

They launched and landed a booster for its 22nd time earlier. A new record

[LivLL]

May sound completely stupid but as a layman would it be possible to gently thrust it out of Earth orbit and position is somewhere so that it remains forever ( bit like the Tesla Roadster in space ). Seems a shame to just burn it up in the atmosphere

[skwdenyer]

Caruso said:

Beati Dogu said:

Well that was fun and double landings will always be cool.


Unrelated, but interesting nonetheless: NASA have awarded SpaceX a ~$850 million contract to deorbit the ISS after it is retired in 2030.

https://www.nasa.gov/news-release/nasa-selects-int...

Interesting I wonder what hardware they will develop for that and how it will be done I.e. in sections or as a whole?

This will be another Starship variant, I'd imagine, refuelled in-orbit so as to be able to provide the necessary thrust. The publicly-disclosed plan is to bring it dow in one piece.

[ChocolateFrog]

skwdenyer said:

Caruso said:

Beati Dogu said:

Well that was fun and double landings will always be cool.


Unrelated, but interesting nonetheless: NASA have awarded SpaceX a ~$850 million contract to deorbit the ISS after it is retired in 2030.

https://www.nasa.gov/news-release/nasa-selects-int...

Interesting I wonder what hardware they will develop for that and how it will be done I.e. in sections or as a whole?

This will be another Starship variant, I'd imagine, refuelled in-orbit so as to be able to provide the necessary thrust. The publicly-disclosed plan is to bring it dow in one piece.

Surely the timing of the burn is much more critical than the amount of thrust.

Should only need a small amount. The atmosphere will do the rest.

[skwdenyer]

ChocolateFrog said:

skwdenyer said:

Caruso said:

Beati Dogu said:

Well that was fun and double landings will always be cool.


Unrelated, but interesting nonetheless: NASA have awarded SpaceX a ~$850 million contract to deorbit the ISS after it is retired in 2030.

https://www.nasa.gov/news-release/nasa-selects-int...

Interesting I wonder what hardware they will develop for that and how it will be done I.e. in sections or as a whole?

This will be another Starship variant, I'd imagine, refuelled in-orbit so as to be able to provide the necessary thrust. The publicly-disclosed plan is to bring it dow in one piece.

Surely the timing of the burn is much more critical than the amount of thrust.

Should only need a small amount. The atmosphere will do the rest.

According to NASA, substantial thrust is needed, because ISS is so large and it’s burn-up characteristics so relatively little-understood that a substantial burn is needed to ensure the surviving pieces hit the right point in the Pacific.

[Grey_Area]

Place it at a Lagrange point. Either L1,2,3 surely that would do.

[Dog Star]

Grey_Area said:

Place it at a Lagrange point. Either L1,2,3 surely that would do.

Which would require an unfeasible amount of energy - it’s going 17500 or so mph now and would need to get up to about 25000 mph and it weighs several hundred tons.

[SpudLink]

skwdenyer said:

ChocolateFrog said:

skwdenyer said:

Caruso said:

Beati Dogu said:

Well that was fun and double landings will always be cool.


Unrelated, but interesting nonetheless: NASA have awarded SpaceX a ~$850 million contract to deorbit the ISS after it is retired in 2030.

https://www.nasa.gov/news-release/nasa-selects-int...

Interesting I wonder what hardware they will develop for that and how it will be done I.e. in sections or as a whole?

This will be another Starship variant, I'd imagine, refuelled in-orbit so as to be able to provide the necessary thrust. The publicly-disclosed plan is to bring it dow in one piece.

Surely the timing of the burn is much more critical than the amount of thrust.

Should only need a small amount. The atmosphere will do the rest.

According to NASA, substantial thrust is needed, because ISS is so large and it’s burn-up characteristics so relatively little-understood that a substantial burn is needed to ensure the surviving pieces hit the right point in the Pacific.

If they only gave it a slight push into the upper atmosphere, I can imagine the ISS breaking off a big piece every few thousand miles, with no idea where they will end up.

[MartG]

SpudLink said:

skwdenyer said:

ChocolateFrog said:

skwdenyer said:

Caruso said:

Beati Dogu said:

Well that was fun and double landings will always be cool.


Unrelated, but interesting nonetheless: NASA have awarded SpaceX a ~$850 million contract to deorbit the ISS after it is retired in 2030.

https://www.nasa.gov/news-release/nasa-selects-int...

Interesting I wonder what hardware they will develop for that and how it will be done I.e. in sections or as a whole?

This will be another Starship variant, I'd imagine, refuelled in-orbit so as to be able to provide the necessary thrust. The publicly-disclosed plan is to bring it dow in one piece.

Surely the timing of the burn is much more critical than the amount of thrust.

Should only need a small amount. The atmosphere will do the rest.

According to NASA, substantial thrust is needed, because ISS is so large and it’s burn-up characteristics so relatively little-understood that a substantial burn is needed to ensure the surviving pieces hit the right point in the Pacific.

If they only gave it a slight push into the upper atmosphere, I can imagine the ISS breaking off a big piece every few thousand miles, with no idea where they will end up.

Yes - they need to give it a big enough push to ensure it comes down at a fairly steep angle to be sure it hits the right area aroun d Point Nemo

[xeny]

Dog Star said:

Grey_Area said:

Place it at a Lagrange point. Either L1,2,3 surely that would do.

Which would require an unfeasible amount of energy - it’s going 17500 or so mph now and would need to get up to about 25000 mph and it weighs several hundred tons.

I thought L1 at least was relatively undemanding to get to from an energy perspective?

[Solocle]

xeny said:

I thought L1 at least was relatively undemanding to get to from an energy perspective?

It's the minimal energy. But to reach Earth-Moon L1, you still basically need the same energy requirements as a trip to the Moon.

You need 3.1 km/s Δv to get from LEO to a lunar transfer orbit.

To reach escape velocity from a lunar transfer orbit, you need an extra 93 m/s.

So if you have the fuel for a lunar transfer, actually it's going to be super easy, barely an inconvenience.

Heck, A gravity assist from the moon can give you some delta-V for free.

There are neat tricks with N-body gravitation, but you basically need to get to the moon for them to have an effect.

[SpudLink]

Solocle said:

... super easy, barely an inconvenience...