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I am amazed that the post-ignition quick disconnect for a hypergolic fluid is lighter weight than just having a larger tank on board.

I really love it when people are smarter than professionals like Tom Mueller.

Let me say it differently then.

Can someone point out the non obvious thing that makes having the post-ignition quick disconnect preferrable to a bigger tank?

For instance, deleting the quick disconnect means that, should they start the engines and then shut down on the pad, they probably can't try an engine restart without reconnecting, which requires draining the fuel tanks and so on.  Maybe that's the reason.

Your statement contained no information about rockets.

The tail service masts don't release until the hold-downs do. And fluid QD's are very light, very easy to service/replace and when they leak, it's very obvious, neither of which are true for internal fluid tanks and lines.

(DISCLAIMER: I have spec'd/designed fluid QD for crewed spaceflight applications in life-critical operations; I'm not talking out of my ass).

Actually, Herb, I believe that qualifies more as a CLAIMER than a DISCLAIMER.   :)
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I am amazed that the post-ignition quick disconnect for a hypergolic fluid is lighter weight than just having a larger tank on board.

I really love it when people are smarter than professionals like Tom Mueller.

Let me say it differently then.

Can someone point out the non obvious thing that makes having the post-ignition quick disconnect preferrable to a bigger tank?

For instance, deleting the quick disconnect means that, should they start the engines and then shut down on the pad, they probably can't try an engine restart without reconnecting, which requires draining the fuel tanks and so on.  Maybe that's the reason.

Your statement contained no information about rockets.

The tail service masts don't release until the hold-downs do. And fluid QD's are very light, very easy to service/replace and when they leak, it's very obvious, neither of which are true for internal fluid tanks and lines.

(DISCLAIMER: I have spec'd/designed fluid QD for crewed spaceflight applications in life-critical operations; I'm not talking out of my ass).
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Advanced Concepts / Re: Anti-Protons Are Going On A Road Trip
« Last post by QuantumG on Today at 12:27 AM »
So far its been an amazing achievement to make ant-protons. I'm pretty sure "anti-atoms" are not in the offing, whatever they are, or if such a thing could ever exist. So the current project is transporting the current product, for a currently planned investigation, i.e. the anti-proton.

Anti-atoms are atoms made of anti-particles. An anti-proton *is* an anti-atom, but I imagine what you mean is an anti-atom of neutral charge - the simplest of which would be anti-hydrogen, an anti-proton and an anti-electron (times 2). This has been achieved too (in 1995 at CERN). In 2010 and 2011 another project at CERN trapped low energy anti-hydrogen for up to 1000 seconds.

An anti-electron is more typically referred to as a positron.

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The BE-4 would seem to be the main risk by far... first oxygen-rich staged combustion methlox engine in the US.  First orbital engine for Blue.  Started long before Blue/ULA partnership.  I seriously doubt that this will be deemed lower risk than was M1-D and be allowed to only have six BE-4s fly before crew, compared to 70 Block 5 M1-Ds, with multiple restarts -- insight/oversight or not.

And Falcon has engine-out capability which Vulcan won't have... and post-flight inspections.

It can be deemed lower if you care more about checking boxes on the right forms than you do about actual flight performance.
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SpaceX Reusable Rockets Section / Re: Fairing reuse
« Last post by envy887 on Today at 12:16 AM »
Because the barge can't go fast enough.

I'm guessing one reason for a fast boat is because the landing area onboard is to small, so you make it up repositioning the boat.

LouScheffer seems correct: the parafoil cannot hover, so the boat needs to match its forward speed as best it can or else that energy has to be taken out by the net.  The coincidence in parafoil speed and Mr. Steven's speed seems strong. Can't tow a barge nearly fast enough to make a meaningful contribution.

If the boat also needs to sprint to a computed landing target, you can't possibly make a net-on-barge as big as the distance Mr. Steven could sprint at 32kts even in the few minutes after parachute deploy.

But it can target a fixed location to within a certain positional error. Just have t make sure the positional error is smaller than the landing area.
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I think people might be giving these prices a little too much credibility. How can expended side boosters raise the price $55 million, but an expended core only $5 million?

SpaceX can charge whatever price they want. An expended F9 could be $6 billion per flight and reused FH 3 for a nickel. Who says it has to make sense?
The people who pay the bill.

Who won't be complaining if SpaceX offers almost triple the performance for only $5 million more.
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Commercial Space Flight General / Re: Sea Launch Future
« Last post by Space Ghost 1962 on Today at 12:11 AM »
It's a symptom of large dysfunction in Russia/Ukraine. Unsurprising.

Large scale economic issues exist that have blocked various different launcher manufacturing/supply chain/operations. As things freeze up in one launcher, costs rise too much, becomes less attractive, another may become more attractive by means of a manipulation/funds passed through intermediaries, and that gets propped up to cobble together some cash flow to float a few missions. Rob Peter to pay Paul, circle back to spot some change to Peter.

Zenit was very economic for what it could do (although compromised with the BIM startup if launch couldn't proceed, reminds of Concorde not being able to stop after reaching V1, committing to Vr). Now perhaps that is once again desired, but a lot has changed in the meantime that many are in denial over.

You can never tell with all the false starts and diktats and schemes, if anything will ever happen. During the pursuit of Zenit, it might be that another choice presents itself, or one/another frustrates and its back to Zenit again. Counting on consistency at this point isn't wise.

The big men have little concern and no patience/character.
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SpaceX Reusable Rockets Section / Re: Fairing reuse
« Last post by cscott on Today at 12:07 AM »
Because the barge can't go fast enough.

I'm guessing one reason for a fast boat is because the landing area onboard is to small, so you make it up repositioning the boat.

LouScheffer seems correct: the parafoil cannot hover, so the boat needs to match its forward speed as best it can or else that energy has to be taken out by the net.  The coincidence in parafoil speed and Mr. Steven's speed seems strong. Can't tow a barge nearly fast enough to make a meaningful contribution.

If the boat also needs to sprint to a computed landing target, you can't possibly make a net-on-barge as big as the distance Mr. Steven could sprint at 32kts even in the few minutes after parachute deploy.

32 knots = 16.462 meters per second. That's almost a kilometer in a single minute of descent time.

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