SpaceX Falcon Heavy Discussion (Thread 6)

[envy887]

I wouldn't dismiss the Falcon family so soon. Plans change to accommodate changing conditions all the time. I know Musk is promoting Starship, as he should, but I believe there will continue to be a market for Falcon and Dragon for some time to come. Especially now that they are both reusable I'd be willing to bet that he'll keep an assembly/refurb line going, even if it's slow paced, just to support that market , which will continue to grow. He's not going to cede that market to someone else, especially since it will continue to generate much needed cash for the Starship HSF program. Colonizing Mars is going to be really expensive and the Falcon-9 and Falcon-H have a long term role to play in contributing to that funding need.

Remember, Elon signed a 20-year lease for Launch Complex 39A and there has been a *LOT* of SpaceX money sunk into it. He'll be wanting to make a really good ROI from that.

Starship will fly, but its OML is not well suited to satellite delivery, which are designed to ride at and be inserted from the top. I know there are designs out there like Chomper, but that's a long way off imo. He's got too much else on his plate at the moment. Falcon will be the SpaceX satellite delivery system of record for some time to come.

Falcon will be around until Starship is cheaper to operate and more reliable and Falcon's customers move onto it. That might take 5, 10 or 20 years, but it will happen.

[meekGee]

If there is one thing we know about Elon? That he doesn't subscribe to the sunk cost fallacy.

It depends entirely on whether or not he is making or losing money while getting the ROI.
If he is then he subscribes - until he's not. Then he doesn't.
He know when to hold 'em and when to fold 'em.

FWIW Musk was very explicit about the planb

Stop making new F9 S1s1, stock up on F9 S2s, turn fully to SS/SH, and complete the switch before F9 fleet reaches end of life.

[meekGee]

I wouldn't dismiss the Falcon family so soon. Plans change to accommodate changing conditions all the time. I know Musk is promoting Starship, as he should, but I believe there will continue to be a market for Falcon and Dragon for some time to come. Especially now that they are both reusable I'd be willing to bet that he'll keep an assembly/refurb line going, even if it's slow paced, just to support that market , which will continue to grow. He's not going to cede that market to someone else, especially since it will continue to generate much needed cash for the Starship HSF program. Colonizing Mars is going to be really expensive and the Falcon-9 and Falcon-H have a long term role to play in contributing to that funding need.

Remember, Elon signed a 20-year lease for Launch Complex 39A and there has been a *LOT* of SpaceX money sunk into it. He'll be wanting to make a really good ROI from that.

Starship will fly, but its OML is not well suited to satellite delivery, which are designed to ride at and be inserted from the top. I know there are designs out there like Chomper, but that's a long way off imo. He's got too much else on his plate at the moment. Falcon will be the SpaceX satellite delivery system of record for some time to come.

Falcon will be around until Starship is cheaper to operate and more reliable and Falcon's customers move onto it. That might take 5, 10 or 20 years, but it will happen.

My guess is less than 5.  Remember the whole entirety of F9 life is 10 years so far, and SpaceX today is able to move a lot faster than it could 10-15 years ago.

Once SS/SH flies, the reusable nature of the vehicle will accelerate progress.

[clongton]

Stop making new F9 S1s1, stock up on F9 S2s, turn fully to SS/SH, and complete the switch before F9 fleet reaches end of life.

Yes - That's the plan. But like I said above "Plans change to accommodate changing conditions all the time".
I expect to see an emerging market that F9 & FH will fill long before SS is ready for commercial markets.

My guess is less than 5.

Too soon. Falcon speed of deployment does not apply. The early starships are slated for Mars, not commerce, and their shakedown flights will last months, not minutes.

[meekGee]

Stop making new F9 S1s1, stock up on F9 S2s, turn fully to SS/SH, and complete the switch before F9 fleet reaches end of life.

Yes - That's the plan. But like I said above "Plans change to accommodate changing conditions all the time".
I expect to see an emerging market that F9 & FH will fill long before SS is ready for commercial markets.

Curious - what market are you thinking of, and what time frame?

Remember that even under the current plan, the F9 fleet will launch Starlink v1, so hundreds of launches.

What or who can add a significant amount to that?

[clongton]

Curious - what market are you thinking of, and what time frame?

Remember that even under the current plan, the F9 fleet will launch Starlink v1, so hundreds of launches.
What or who can add a significant amount to that?

DoD, NASA (ISS will be replaced and need building and then servicing), Commercial stations leased to universities, NGOs and nations wanting a space program.

[envy887]

My guess is less than 5.

Too soon. Falcon speed of deployment does not apply. The early starships are slated for Mars, not commerce, and their shakedown flights will last months, not minutes.

I agree with that conclusion, but not the reasoning. If anything, SpaceX is developing Starship faster than Falcon, and for every flight to Mars or the Moon (recall that dearmoon is the only paying customer on the manifest so far) they need lots of refueling flights in rapid succession. Shakedown won't be a problem.

But Falcon is a reliable architecture with risk-averse customers like DoD and NASA. They are only now starting to launch of Falcon Heavy, and are both inherently slow and very cautious about adopting new vehicles. SpaceX isn't going to have as easy a time shutting down F9 and FH as they did Falcon 1.

[meekGee]

Curious - what market are you thinking of, and what time frame?

Remember that even under the current plan, the F9 fleet will launch Starlink v1, so hundreds of launches.
What or who can add a significant amount to that?

DoD, NASA (ISS will be replaced and need building and then servicing), Commercial stations leased to universities, NGOs and nations wanting a space program.

I believe none of these, in the next 5 years, will do anything but talk.

DoD maybe, but not in enough volume to matter.

ISS replacement, at full NASA/ESA speed, nah.

Commercial stations - who, Bigelow?  Come on.

Universities and NGOs will become starship customers.  It's a lot more interesting to do research on Mars (or moon or whatever) then in LEO.

[meekGee]

My guess is less than 5.

Too soon. Falcon speed of deployment does not apply. The early starships are slated for Mars, not commerce, and their shakedown flights will last months, not minutes.

I agree with that conclusion, but not the reasoning. If anything, SpaceX is developing Starship faster than Falcon, and for every flight to Mars or the Moon (recall that dearmoon is the only paying customer on the manifest so far) they need lots of refueling flights in rapid succession. Shakedown won't be a problem.

But Falcon is a reliable architecture with risk-averse customers like DoD and NASA. They are only now starting to launch of Falcon Heavy, and are both inherently slow and very cautious about adopting new vehicles. SpaceX isn't going to have as easy a time shutting down F9 and FH as they did Falcon 1.

You're forgetting that for every SS that goes to Mars, there's SH capacity left on earth, plus a bunch of tankers...

Tankers can be used as deployers, or, given the capacity to build multiple SSs, a couple of deployers is all you need since they come back a day or two later.

[Proponent]

Finally, I put this in a spreadsheet where you enter the apogee of the injection burn (166 km for the NASA numbers)....

Nice work.  How do you know the injection altitude is 166 km?

[yokem55]

https://twitter.com/elonmusk/status/1111805464797302784

I'm wondering what he means by direct GEO requiring a fully expended falcon heavy? Just to outperform Delta Heavy? Or for any payload direct to GEO? Just core expended should get them a pretty decent payload to GEO...

[cppetrie]

https://twitter.com/elonmusk/status/1111805464797302784

I'm wondering what he means by direct GEO requiring a fully expended falcon heavy? Just to outperform Delta Heavy? Or for any payload direct to GEO? Just core expended should get them a pretty decent payload to GEO...

I think he meant for payloads exceeding DIV and A5 max capacity to GEO it needs to go expendable.

[whitelancer64]

I'm wondering what he means by direct GEO requiring a fully expended falcon heavy? Just to outperform Delta Heavy? Or for any payload direct to GEO? Just core expended should get them a pretty decent payload to GEO...

Falcon family currently does GTO launches, meaning the satellite has to do part of the work to put itself into GEO.

Direct to GEO means the rocket does all the work to put the satellite into orbit.

[rpapo]

Direct to GEO means the rocket does all the work to put the satellite into orbit.

Meaning that apart from providing the boost to lift the apogee to 35786km, the second stage must then stay alive for some six hours plus in order to ignite again, raise the perigee to the same altitude, release the satellite in its orbit, and then ignite twice more to raise its own orbit to the "graveyard" area.

Or, if it has enough fuel left, escape to a solar orbit.

All of which explains some of the long duration experiments they did with the first Falcon Heavy launch, and on some other launches since.

[speedevil]

Direct to GEO means the rocket does all the work to put the satellite into orbit.

Meaning that apart from providing the boost to lift the apogee to 35786km, the second stage must then stay alive for some six hours plus in order to ignite again, raise the perigee to the same altitude, release the satellite in its orbit, and then ignite twice more to raise its own orbit to the "graveyard" area.

Or, if it has enough fuel left, escape to a solar orbit.

All of which explains some of the long duration experiments they did with the first Falcon Heavy launch, and on some other launches since.

Does this put (possibly weak) constraints on lifetime of the stage?
Is there enough data to guess at what the maximum boiloff might be in this situation for 6 hours, and to extrapolate for 80 hours?

[rpapo]

Does this put (possibly weak) constraints on lifetime of the stage?

On the minimum lifetime, certainly.  Only SpaceX (and NASA, and the DOD) know for sure, but at this point I'd say the stage can last at least to the perigee raising maneuver.  How much longer I cannot say.  The maneuver to raise the orbit to the graveyard region, done by the book, would require the stage to stay alive at least another twelve hours.  There may be some shortcuts, more costly in fuel, to get that done quicker.

Is there enough data to guess at what the maximum boiloff might be in this situation for 6 hours, and to extrapolate for 80 hours?

I have no idea myself.  But I would think it more complicated than just boil-off of the LOX.  You almost must consider the possible cooling/thickening/freezing of the RP-1, the formation of crystals blocking critical valves, the battery life for the controls and so on.  Oh, and ullage thrusters must continue to function too.  There are many things that go into how long the stage will survive in a functional state.

[speedevil]

Does this put (possibly weak) constraints on lifetime of the stage?

On the minimum lifetime, certainly.  Only SpaceX (and NASA, and the DOD) know for sure, but at this point I'd say the stage can last at least to the perigee raising maneuver.  How much longer I cannot say.  The maneuver to raise the orbit to the graveyard region, done by the book, would require the stage to stay alive at least another twelve hours.  There may be some shortcuts, more costly in fuel, to get that done quicker.

I guess there is a constraint there - if boiloff is more than ~1.5 tons/12 hours, you may as well just burn for lunar aided escape/impact.

[LouScheffer]

Finally, I put this in a spreadsheet where you enter the apogee of the injection burn (166 km for the NASA numbers)....

Nice work.  How do you know the injection altitude is 166 km?

A reasonable question.  I thought I saw a document stating that the high energy LSP predictions used a 90 nmi (166.7 km) parking orbit, but I can't find it by searching now.   It is the value used in the Atlas 5 user's guide, though, so maybe I assumed the value for Atlas was used by everyone.

The Falcon 9 user manual (early 2019 edition) does not specify a parking orbit for high energy missions.   It does specify a baseline parking orbit for GTO, however, which is 185 km (100 miles).  If you assume this value for high energy missions as well, then re-optimize for the other parameters, you get just as good of a fit, with a final mass that only differs by 10 kg.  In fact it's slightly more realistic fit - we now know that that the second stage fuel is 105,700 kg from the environmental impact statement for the SpaceX launch abort.  Add the roughly 4.5t empty mass of the second stage, and the mass of the stage+fuel (but not payload) should be about 110,200 kg.  The 185 km parking orbit fit is closer to this value than the 166 km version.

[groundbound]

LouScheffer: can you explain something above? (I won't quote in interests of brevity)

How do you come up with 185 km = 100 miles? Is there something I am missing in the unit conversion? I get 115 miles. Is using nautical miles standard for orbit calculations?

[docmordrid]

>
How do you come up with 185 km = 100 miles? Is there something I am missing in the unit conversion? I get 115 miles. Is using nautical miles standard for orbit calculations?

185km = 99.9 nautical miles