Speaking of corrections, I was surprised at how active the nitrogen thrusters were between the boostback burn and the re-entry burn.
I read somewhere that there are alot of tiny thrusts to settle the fuel in the tanks ie. reduce the sloshing so the feed is good for re-fire. I don't think that makes much difference to the overall trajectory or orientation.
I would suggest the thrusters are key to orientation prior to the boost back, and then getting the orientation stable for re-entry and maybe at the bottom when at the hover stage on windy days? I hadn't thought about the fuel and oxygen sloshing around but it would be several hundred kilos bouncing around in two almost empty tanks.
I would think if there was any rotation (pitch / yaw) when engines were started it would be bad thing if there was an atmosphere about.
I'm still amazed about the flight controls. When you think about them, each have very large variations in their performance, the paddles will generate no change in direction at low speed or low pressures but at supersonic speeds that drag would be huge, the engine's gimbolling have greater effect depending on the thrust, but the thrust profile is very limited in time and power, the drag and lift from the fuselage's flight angle etc. Then there is variable of wind and pressure on decent.
... and it's all automated. (could a human be trained to land it?)
I'm desperately trying to remember where I read it, but the implication was that there were either two strengths of thrusters, or the one thruster type with varying thrust. The word 'ullage' comes to mind.
It is an amazing craft that has three very different modes/categories of operation, for which SpaceX has successfully encompassed plus transitions. For the most part it is in unstable equilibrium ie. a pencil standing on it's end. For example get a long narrow cardboard tube and then run around with it sitting on the palm of one hand. Try to keep it pointing upwards. You will see the basic issue : it can go really wrong, really quickly. There is a precious envelope of safety.
Cheers, Mike.
Ullage is the right word followed by rocket or motor. While that rocket is in free fall so is the fuel in the tank. They can only do so much with the surface tension and internal baffles to get it do behave. They have to be sure when the fuel is called for that it is at the pickup. You don't want to vent your pressurizing gas out into the combustion chamber! So you need an ullage rocket to gently take the beast out of zero g and put a small positive g on it so the fuel is at the pickup. Once the main fires it will take that job over.
As to the relight, remember the combustion takes place out of the slipstream, in a chamber. It is just the exhaust gas you see and any excess fuel and oxidizer. Remember F=delta M * V. The more that burns inside the chamber the higher the V of the exhaust. The delta M is how wide you open the throttle valve.
Launch site: LC-39A, Kennedy Space Center, Florida
However at 6100 kg heading to GTO it's almost certainly going to toss the first stage altogether. That payload is well above the greatest ever recovered via barge. At one time it was on the Falcon Heavy manifest.
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
A lot of tension when the crew thought they were headed to Mars and, instead, discovered they were heading directly into the Sun !
(I hate it when that happens )
Also ... on that end of movie landing on the floating offshore platform. I noticed that they burned a awful lot of fuel on that landing as, they started 'hovering' way up there.
If Musk had been there to advise them, they would no doubt come in fast and THEN ramp up the engines.
thought they were headed to Mars and, instead, discovered they were heading directly into the Sun
<snip>
burned a awful lot of fuel on that landing as, they started 'hovering' way up there.
The extra delta-V required to first accidentally head directly toward the Sun, then recover from it, makes the gravity losses from a wee bit of hovering look paltry in comparison.
The one unchangeable thing in science fiction films seems to be that few even try to get the dynamics to be remotely plausible.
thought they were headed to Mars and, instead, discovered they were heading directly into the Sun
<snip>
burned a awful lot of fuel on that landing as, they started 'hovering' way up there.
The extra delta-V required to first accidentally head directly toward the Sun, then recover from it, makes the gravity losses from a wee bit of hovering look paltry in comparison.
The one unchangeable thing in science fiction films seems to be that few even try to get the dynamics to be remotely plausible.
I can forgive a 1959 movie for getting orbit stuff bad wrong. We had not even attempted to do a rendezvous in space at that time. First time NASA tried they got it backwards! It is counter intuitive. To catch up, you slow down!
Mike Hewson wrote:AgentB
)
Ullage is the right word followed by rocket or motor. While that rocket is in free fall so is the fuel in the tank. They can only do so much with the surface tension and internal baffles to get it do behave. They have to be sure when the fuel is called for that it is at the pickup. You don't want to vent your pressurizing gas out into the combustion chamber! So you need an ullage rocket to gently take the beast out of zero g and put a small positive g on it so the fuel is at the pickup. Once the main fires it will take that job over.
As to the relight, remember the combustion takes place out of the slipstream, in a chamber. It is just the exhaust gas you see and any excess fuel and oxidizer. Remember F=delta M * V. The more that burns inside the chamber the higher the V of the exhaust. The delta M is how wide you open the throttle valve.
I find myself feeling rather
)
I find myself feeling rather greedy for another great show ! ;-)
It would seem that SpaceflightNow have :
May 15 Falcon 9 • Inmarsat 5 F4
Launch window: 2320-0010 GMT (7:20-8:10 p.m. EDT)
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
Mike Hewson wrote: @Bill : I
)
I watched it ! Wow, fantastic !
A lot of tension when the crew thought they were headed to Mars and, instead, discovered they were heading directly into the Sun !
(I hate it when that happens )
Also ... on that end of movie landing on the floating offshore platform. I noticed that they burned a awful lot of fuel on that landing as, they started 'hovering' way up there.
If Musk had been there to advise them, they would no doubt come in fast and THEN ramp up the engines.
(Like Falcon 9 )
Bill
.
AgentB wrote:Ariane 5 VA236
)
When they light the solids, it leaps of the pad! No plan B.
AgentB wrote:AgentB
)
Does it what, eh ? :-)
In one minute it is 10km up. You know, if you could re-seal the ends after use the boosters would float quite nicely ..... iris diaphragm anyone ?
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
Bill592 wrote:thought they
)
The extra delta-V required to first accidentally head directly toward the Sun, then recover from it, makes the gravity losses from a wee bit of hovering look paltry in comparison.
The one unchangeable thing in science fiction films seems to be that few even try to get the dynamics to be remotely plausible.
archae86 wrote:Bill592
)
I can forgive a 1959 movie for getting orbit stuff bad wrong. We had not even attempted to do a rendezvous in space at that time. First time NASA tried they got it backwards! It is counter intuitive. To catch up, you slow down!
Per SpaceX tweet
)
Per SpaceX tweet :
BTW : it was held down by duct tape. :-)
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
Static fire for Monday's
)
Static fire for Monday's launch : no legs nor fins ....
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
Apparently this was scheduled
)
Apparently this was scheduled to go on a Falcon Heavy but with the improvements on F9 - it will be the heaviest F9 payload to GTO.
When the FH is ready the test firings will be something to see.