Author Topic: Falcon Heavy Demo Mission Payload Discussion  (Read 141068 times)

Offline acsawdey

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Re: Falcon Heavy Demo Mission Payload Discussion
« Reply #660 on: 03/13/2018 06:41 pm »
Teslas use electric brakes:

Solenoid, not hydraulic.  (Granted, not 100% sure this is was the case for 1st Gen roadster, but likely.)
Those still have a hydraulic piston. The "electric" part is a pump and a solenoid valve that pressurize and control the hydraulic circuit.

However, brake hydraulics are built to take hundred of atmospheres of pressure. They wouldn't even notice a little vacuum, nevermind explode or leak brake fluid.
Not sure I get you. The problem I'd expect would be vacuum causing brake fluid to boil, forcing the pistons out if the rotors were missing. That would take almost no pressure.
I don't see hydraulic brake fluid boiling just because of vacuum.  Its not like blood or any similar fluid.

I found a vapor pressure plot for diethylene glycol (component of some brake fluid) here:

The vapor pressure at room temperature is off-the-chart low (less than 1mm Hg) so I think "boiling" is the wrong word for what would be happening --- "offgassing" is more like it. Especially as the roadster ventured out into interplanetary space and started to cool off. But if I was doing it, I would remove the whole brake system just so as not to have to worry about it while processing/encapsulating the roadster on the ground -- brake fluid is messy noxious stuff. Any gearhead worth their salt ought to be able to pull the master cylinder, lines, and calipers in a couple hours at the most.

Offline deruch

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Re: Falcon Heavy Demo Mission Payload Discussion
« Reply #661 on: 03/13/2018 10:13 pm »
While all this is somewhat interesting in a peripheral sense, I feel that the ongoing conversation on how brakes might work in space has reached the point where it can very faithfully be described as "Polishing the Brass on the Titanic".
Shouldn't reality posts be in "Advanced concepts"?  --Nomadd

Offline Lar

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Re: Falcon Heavy Demo Mission Payload Discussion
« Reply #662 on: 03/13/2018 10:33 pm »
Not the right analogy as this thread isn't sinking. Not even an iceberg in sight...

But can we bring this side thread convo to a full stop?
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY