On 2020-05-23 9:06 PM, JF Mezei wrote:
On 2020-05-23 16:46, David Spain wrote:

https://i.stack.imgur.com/H4RtH.png

Which doesn't really show the pressurization plumbing as far as I can
see.


Nor does it show a dome to terminate the lower end of the O2 tank above
engines.

I was told here quite forcefully here that the Starship/SuperHeavy won't
have helium pressurization.

That is correct. It's autogenous not helium pressurized.

I was also told here that there may be smaller tanks to run the
thrusters. And those round tanks might be those instead of fuel for landing.


No I doubt that. I've seen other diagrams that show a different tank
arrangement for RCS. Some diagrams show it just venting GOX for RCS
control. Here's Elon's take on it:

https://twitter.com/elonmusk/status/1091159618263298048

So cold gas thrusters. That gas can come from anywhere. I could be
wrong, but I suspect the LOX tank. This site also suggests a move
perhaps to a methane based thruster in the future, so who knows?:

https://www.elonx.net/super-heavy-st...ndium/#general

See the penultimate paragraph to the section "Super Heavy Starship System".

Especially for Super Heavy, one would think you'd want as large a single
tank as you could to add versatility (more fuel for launch in a
disposable launcher mode vs use some of that fuel to land after
launching lesser load).

If you dedicate a tank to landing, it's fixed size removes some of that
flexibility.

Yes but you don't need to deal with ullage for restarts in a very nearly
empty tank either.

In the case of super heavy, would it be correct to state that thrusters
would only be used after MECO to turn the rocket around to orient it for
re-entry ? During re-entry per say, are they used or does it rely solely
on the fins for orientation ?


See above link.

Just curiuous to on why thsoe round tanks would be so big.


As I said, for return from orbit. You *are* firing one or more Raptors
for this.

You could have a small tank that is replenished from big tank via a
small pump and heaters to make it gaseous since thrusters wouldn't
typically be use continously for long periods, you'd have time to refill
the small tanks by moving some liquid from big tanks, heat it into gas
into small tank.


Why bother when you can launch with full tanks? All that pumping needed
to get home? No thanks.

Dave