Quote from: andrewsdanj on 05/10/2018 09:43 pmVery interesting - constant thrust of 190klb all the way up rather than constant chamber pressure. Commentator says first stage Merlins will be throttled to maintain 190,000 lbs of thrust as the atmospheric pressure decreases with altitude.This seems like half an explanation. Why would that help?
Very interesting - constant thrust of 190klb all the way up rather than constant chamber pressure.
So, the SpaceX down the side of the first stage is not iced over. Is there a coating or something they could use to keep it from frosting over? (I don't know what a superhydrophobic coating would do on the outside of a subcooled LOX tank.)
Note the SpaceX down the side of S1 is not obscured by frost.edit: beat me to it...Quote from: ClayJar on 05/10/2018 09:55 pmSo, the SpaceX down the side of the first stage is not iced over. Is there a coating or something they could use to keep it from frosting over? (I don't know what a superhydrophobic coating would do on the outside of a subcooled LOX tank.)Might be a bit more than that. Some chatter in earlier threads as to whether there is additional thermal control (beyond superficial). My guess is there is something more than skin deep contributing.
Did he say "review reason why telemerty loss?"
Note that now with more extensive venting (down from above) we are now seeing more frosting-obscuring.
Might be a bit more than that. Some chatter in earlier threads as to whether there is additional thermal control (beyond superficial). My guess is there is something more than skin deep contributing.
Maybe the less frosting was due to the faster LOX load, and given enough time it frosts over just as much as before?
It was interesting to see the Rainbirds come on for a little bit after the abort. Possibly part of the abort process?
Quote from: joek on 05/10/2018 09:56 pmMight be a bit more than that. Some chatter in earlier threads as to whether there is additional thermal control (beyond superficial). My guess is there is something more than skin deep contributing.A frost-resistant coating seems like it would likely be easy enough, and I don' t imagine active frost prevention would be desirable (since it would increase propellant heating). Whatever it is, it's only frost-resistant, as this long hold has given it sufficient time to get pretty icy. Worked well through the original cryogen-loading-to-launch span, at least.Quote from: abaddon on 05/10/2018 10:06 pmMaybe the less frosting was due to the faster LOX load, and given enough time it frosts over just as much as before?The "SpaceX" was on a distinctly different-looking patch, even early in LOX loading. It appeared that the stage overall was icing as usual, but that a rectangle was treated somehow.
If I remember right, when SpaceX went to subcooled LOX, temperature issues meant they were basically committed to a window of a few seconds (basically, no chance for a hold, so a hold would be a scrubd). But that does not appear to be the case today - they appear to at least have the capability to hold.And I too am intrigued by the lack of frost. There should be plenty over the LOX tank. My guess is Clayjar's guess is right, some sort of coating. And dang, a scrub!
Quote from: CJ on 05/10/2018 10:14 pmIf I remember right, when SpaceX went to subcooled LOX, temperature issues meant they were basically committed to a window of a few seconds (basically, no chance for a hold, so a hold would be a scrubd). But that does not appear to be the case today - they appear to at least have the capability to hold.And I too am intrigued by the lack of frost. There should be plenty over the LOX tank. My guess is Clayjar's guess is right, some sort of coating. And dang, a scrub!One thing to keep in mind is that may have been true at the time (although I think it was speculation), but 39A has at least the capacity to fill a FH and as such should be able to keep subcooled props topped off considerably longer.
