The original hold was for some type of unauthorized surface vessel in the surrounding waters. They should give this jackass the bill for a "held launch".
They just announced a "scrub" for this flight. No official launch time known at this time.
Launch aborted on low thrust alarm. Rising oxygen temps due to hold for boat and helium bubble triggered alarm.
Originally the backup date for Sunday was Monday tomorrow. I don't have a good guess whether they can or want to recycle from the particular events of today that fast.
So I guess that's the price of deep cryo : a shorter window of opportunity.
The pressurised helium goes into the LOX tank to push it out and to the engine. The bubble in the helium tank makes the entire helium volume much more compliant/compressible - than pure liquid state - and thus lowers that pressure impetus to the LOX. You may be familiar with this effect in hydraulic lines for a car's braking system, the pedal goes squashy if there is air in the lines and a pad change often involves a bleed to remove any gas-in-liquid as well. Ditto for any liquid system that is meant to transit a pressure effect. On short times scales at least the helium and LOX are immiscible, meaning they don't mix much or if you like either doesn't dissolve in the other very well.
Interestingly at high gee the LOX feed is enhanced by that acceleration alone, but at startup you don't have that yet. That is one reason why the Helium tank is no where near the size of the LOX tank. IIRC it is the LOX feed that kicks off the turbo pump.
Cheers, Mike.
( edit ) If there was a mechanism to do it you could remove the bubble by actively re-pressurising at the higher temperature ( slide up the PV hyperbola ). But then the tank ruptures ... been there, got that T-shirt ....
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Elon Musk tweeted a few minutes ago that they are pushing the launch to Friday (presumably by USA east coast time) because of excessive high level wind for the try today.
Launch update
Unfortunately upper-level winds continue to exceed acceptable limits and are expected to get worse as we approach tonight’s launch window, so we are forgoing today’s launch attempt. Winds are forecast to exceed acceptable limits through Thursday. Our team will continue working with the Air Force’s Launch Weather Officer to evaluate the best available opportunity for flight in the coming days.
I'd interpret "upper-level winds" as jet stream ie. several hundred kilometers per hour plus shear on the way up.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
He did say shear specifically, and used language implying concern about forces on the vehicle, not orbital performance, attitude control, or such. He also included this image in his post
That peak is only about 150 miles per hour in the king's units, but it changes rather quickly with altitude at altitudes where the air density is high enough to have some real oomph, and the vehicle has picked up enough speed to ride that rough road rather harshly.
I omitted the word shear from my post, which was sloppy.
Yep, it's an integrity of the vehicle thingy. The rigidity of the frame/barrel, with much of that coming from internal pressurisation, is normally sufficient for longitudinal loads. But if there is a lateral load, or more precisely a difference in the lateral loading along the length of the rocket, then it will crumple/split etc. That makes the gradient of the change of the lateral dynamic pressure ( which we have called wind shear ) a very key point.
The other aspect is the transitioning across turbulent layers that inevitably form when considerable shear is present. I include a change in the direction of the wind as well as speed here. Recall 'virga' : you see the rain falling from the clouds high up but it doesn't appear to reach the ground. There are several causes of that, but often that is due to updrafts and turbulence around wind shear altitudes. I recall from my light flying days being told to always avoid virga, due to the bumpy ride and even occasional reports of damage. Locally I see them in advance of a cold front and you can even spot from cloud patterns the evident changes in wind direction. Cirrus/stratus/cirrostratus is the give away for the jet stream vectors.
As you say the effective momentum hit from the onrushing air is not trivial, the Falcon is supersonic by then and the air is quite 'hard'.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Misfire ? Cheers,
)
Misfire ?
Cheers, Mike.
( edit ) On the upside : in the days of yore when a rocket did that, the rocket plus the entire launch pad was toast.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
The original hold was for
)
The original hold was for some type of unauthorized surface vessel in the surrounding waters. They should give this jackass the bill for a "held launch".
They just announced a "scrub" for this flight. No official launch time known at this time.
Elon himself
)
Elon himself tweeted:
Originally the backup date for Sunday was Monday tomorrow. I don't have a good guess whether they can or want to recycle from the particular events of today that fast.
So I guess that's the price
)
So I guess that's the price of deep cryo : a shorter window of opportunity.
The pressurised helium goes into the LOX tank to push it out and to the engine. The bubble in the helium tank makes the entire helium volume much more compliant/compressible - than pure liquid state - and thus lowers that pressure impetus to the LOX. You may be familiar with this effect in hydraulic lines for a car's braking system, the pedal goes squashy if there is air in the lines and a pad change often involves a bleed to remove any gas-in-liquid as well. Ditto for any liquid system that is meant to transit a pressure effect. On short times scales at least the helium and LOX are immiscible, meaning they don't mix much or if you like either doesn't dissolve in the other very well.
Interestingly at high gee the LOX feed is enhanced by that acceleration alone, but at startup you don't have that yet. That is one reason why the Helium tank is no where near the size of the LOX tank. IIRC it is the LOX feed that kicks off the turbo pump.
Cheers, Mike.
( edit ) If there was a mechanism to do it you could remove the bubble by actively re-pressurising at the higher temperature ( slide up the PV hyperbola ). But then the tank ruptures ... been there, got that T-shirt ....
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
That site is now showing the
)
That site is now showing the time elapsed since the last launch date which was scrubbed.
https://spacexstats.com/#NextLaunch
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now
SpaceX sez : "Wed, Mar 2 2016
)
SpaceX sez : "Wed, Mar 2 2016 10:35 AM AEDT — Wed, Mar 2 2016 12:05 PM AEDT"
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Elon Musk tweeted a few
)
Elon Musk tweeted a few minutes ago that they are pushing the launch to Friday (presumably by USA east coast time) because of excessive high level wind for the try today.
RE: Launch
)
I'd interpret "upper-level winds" as jet stream ie. several hundred kilometers per hour plus shear on the way up.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
He did say shear
)
He did say shear specifically, and used language implying concern about forces on the vehicle, not orbital performance, attitude control, or such. He also included this image in his post
That peak is only about 150 miles per hour in the king's units, but it changes rather quickly with altitude at altitudes where the air density is high enough to have some real oomph, and the vehicle has picked up enough speed to ride that rough road rather harshly.
I omitted the word shear from my post, which was sloppy.
Yep, it's an integrity of the
)
Yep, it's an integrity of the vehicle thingy. The rigidity of the frame/barrel, with much of that coming from internal pressurisation, is normally sufficient for longitudinal loads. But if there is a lateral load, or more precisely a difference in the lateral loading along the length of the rocket, then it will crumple/split etc. That makes the gradient of the change of the lateral dynamic pressure ( which we have called wind shear ) a very key point.
The other aspect is the transitioning across turbulent layers that inevitably form when considerable shear is present. I include a change in the direction of the wind as well as speed here. Recall 'virga' : you see the rain falling from the clouds high up but it doesn't appear to reach the ground. There are several causes of that, but often that is due to updrafts and turbulence around wind shear altitudes. I recall from my light flying days being told to always avoid virga, due to the bumpy ride and even occasional reports of damage. Locally I see them in advance of a cold front and you can even spot from cloud patterns the evident changes in wind direction. Cirrus/stratus/cirrostratus is the give away for the jet stream vectors.
As you say the effective momentum hit from the onrushing air is not trivial, the Falcon is supersonic by then and the air is quite 'hard'.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal