In article ,
says...

On 2018-05-25 20:46, Fred J. McCall wrote:

I don't consider it a risk any more than doing it the other way.

From a performance point of view, isn't SpaceX concerned about having
the kerosene fuel as cold as possible? (aka: loaded only at last minute)

Doesn't LOX remain cold naturally once loaded and the only concern to
have it constantly refilled as some of it boils out?

No. SpaceX cools the LOX almost to the point where it would start to
become solid. They call it "sub-cooled". So if you load it and let it
sit, it warms up to the point that it's at the boiling point of LOX
instead of the much colder "sub-cooled" temperature. As you know from
physics, the colder it gets the more dense it gets. So, they can load
more LOX into the vehicle when it's sub-cooled than when it's at its
boiling point.

They also cool the kerosene for the same reasons. But I'd imagine the
LOX is going to heat up faster because conduction of heat depends on the
difference in temperature between the fluid and the outside ambient
temperature, which is far greater for the LOX than for the kerosene.

Seems to me that loading the He2 under pressure and LOX that surrounds
it is the higher risk part and could be done before they board, and then
load the kerosene at last minute so it is as cold as possible.

Can't do it that way and keep the LOX sub-cooled.

Note: comemrcial aircraft have various restrictions on fueling aircraft
when there are passengers on-board vs boarding/deplaning vs empty. (and
these vary depending on fuel being used).

Cite?

Jeff
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