Here's some fairly good amateur footage i.e. not bad since 10+ km away. There are two sonic booms on record. More of a cracking sound really. There is is one from the lower end and one from the upper end of the stage. The reason for two booms is that the trans-sonic turbulence disrupting a shock wave ( that a boom is the distant evidence of ) doesn't 'disconnect' simultaneously from each end of the barrel. With other, rather more aerodynamic, craft that disconnect is smoother across the airframe and is heard as a single continuous event.
It's also rather cute to see the top venting the cold thruster gas. It seems like a "Phew, I made it down !". :-))
Cheers, Mike.
( edit ) Here's an instagram nicely showing the gimballing of the center engine - a single flame wiggles side to side - indicating thrust vector adjustments right down to contact.
The landing was probably the most impressive so far, but to me it looked like coming in far too fast then slamming on the brakes at the last moment, for a soft landing. deployment of the landing legs were only just about in time as well. They would need to refine that if they intend to transfer people to and from the ISS or even a Moon base. Sticking to replacing stores is probably their real aim. But yes, credit where credit is due, they are getting there.
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now
The landing was probably the most impressive so far, but to me it looked like coming in far too fast then slamming on the brakes at the last moment, for a soft landing. deployment of the landing legs were only just about in time as well. They would need to refine that if they intend to transfer people to and from the ISS or even a Moon base. Sticking to replacing stores is probably their real aim.
There is always room for improvement but not for any reasons you have stated.
I think there is always room for innovation, which Space X are doing. In my ideal world the USA would fund NASA to build and operate a new fleet of modern shuttles. They would primarily be used to ferry people and Science experiments to and from the ISS. Also fund NASA to make a returnable trip to Mars. I would leave Space X as the commercial trucker, delivering and taking away goods. I would also fund NASA to construct Moonbase 1, and look into if Space X could supply the ISS to Moonbase transport for stores.
Space X have improved remarkably in recent times, but there is a long way to go yet. But they are streets ahead of the Europeans Ariane efforts which concentrate upon satellite launches. As I said credit where credit is due.
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now
Thanks ! What a great paper he has written, this is probably the key diagram :
'dispersions' here meaning : how wrong can you be about where you will land ? I think the clue to using a single engine for final/landing burns is hinted too ( my red emphasis ):
Quote:
Small Margin for Error
With most landings, the first attempt must be a success or the vehicle will be destroyed on impact. Moreover, additional propellant is rarely available for a second landing attempt. For large rocket engines, throttling down to a hover is technically challenging and inefficient—every second spent hovering is wasted propellant. For F9R, the rocket has to hit zero velocity at exactly zero altitude. If it reaches zero velocity too low, it will crash; if it reaches zero too high, it will start going back up, at which point cutting the engines and falling is the only option. This requires precise knowledge and control of vertical position and velocity.
Which I interpret as needing a lowest thrust option for the last bit of descent ie. better finesse on total thrust to weight. Of course that is only one strategy, which in turn would depend ( at least ) upon what are the dynamic responses of Merlin engines to throttle changes ..... plus what is worse ? A hard landing under power or a dead drop from some height ? I think it is clear that SpaceX has been exploring the 'hard landing under power' parameter space. :-)))
Cheers, Mike.
( edit ) The Dragon was given bad nav data and docking is delayed. " a 'racetrack' trajectory in front of, above and behind the station " presumably refers to a sequence of positions relative to the ISS ie. a prograde burn to go high & slow and later come in under ( nearer to Earth ).
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
Someone over at the NasaSpaceflight.com site has posted the link to this YouTube video from flight club. It appears to be an assemblage of screens, some directly using available video of the flight, while others are calculated from sources I don't know and with accuracy for which I cannot vouch.
Nevertheless I find the altitude and velocity readouts and profiles for the first stage intriguing and plausible. In particular it's worth noticing how much velocity the first stage picks up descending from the post boost back peak to the reentry burn just before meaningful atmospheric drag begins. It is also interesting to see how very quickly after the end of the reentry burn you can see the deceleration from simple aerodynamics cut in.
It looked to me more gentler
)
It looked to me more gentler than usual too ie. more hover and less slam as it were.
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
Here's some fairly good
)
Here's some fairly good amateur footage i.e. not bad since 10+ km away. There are two sonic booms on record. More of a cracking sound really. There is is one from the lower end and one from the upper end of the stage. The reason for two booms is that the trans-sonic turbulence disrupting a shock wave ( that a boom is the distant evidence of ) doesn't 'disconnect' simultaneously from each end of the barrel. With other, rather more aerodynamic, craft that disconnect is smoother across the airframe and is heard as a single continuous event.
It's also rather cute to see the top venting the cold thruster gas. It seems like a "Phew, I made it down !". :-))
Cheers, Mike.
( edit ) Here's an instagram nicely showing the gimballing of the center engine - a single flame wiggles side to side - indicating thrust vector adjustments right down to contact.
( edit ) The post-launch conference reveals :
- the overnight replacement of a second stage hydraulic actuator to solve the TVC issue.
- the Amos7 investigation is closed and not relevant to this launch.
- the FAA flight approval was not 'late' but simply timely given all variants to consider.
- pad 39A can be turned around for another flight in two weeks.
- after rehab of pad 40 pad it will be generally used for satellites, while 39A is for crewed Dragon and the Heavy.
- they intend to recover all boosters for the Heavy.
- expect another SpaceX launch in about two weeks & from 39A.
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 landing was probably the
)
The landing was probably the most impressive so far, but to me it looked like coming in far too fast then slamming on the brakes at the last moment, for a soft landing. deployment of the landing legs were only just about in time as well. They would need to refine that if they intend to transfer people to and from the ISS or even a Moon base. Sticking to replacing stores is probably their real aim. But yes, credit where credit is due, they are getting there.
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now
Chris S_2 wrote:The landing
)
There is always room for improvement but not for any reasons you have stated.
I think there is always room
)
I think there is always room for innovation, which Space X are doing. In my ideal world the USA would fund NASA to build and operate a new fleet of modern shuttles. They would primarily be used to ferry people and Science experiments to and from the ISS. Also fund NASA to make a returnable trip to Mars. I would leave Space X as the commercial trucker, delivering and taking away goods. I would also fund NASA to construct Moonbase 1, and look into if Space X could supply the ISS to Moonbase transport for stores.
Space X have improved remarkably in recent times, but there is a long way to go yet. But they are streets ahead of the Europeans Ariane efforts which concentrate upon satellite launches. As I said credit where credit is due.
Waiting for Godot & salvation :-)
Why do doctors have to practice?
You'd think they'd have got it right by now
Mike Hewson wrote:Remember
)
Are you sure? i thought SES-10 was supposed to be first re-use. (next month)
AgentB wrote:Mike Hewson
)
You're right. My bad. I misread a statement.
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:AgentB
)
I did hope they had sneakily swapped them over... lol
You wondered earlier about SpaceX landing algorithms, see SpaceX's Lars Blackmore's Research
Thanks ! What a great paper
)
Thanks ! What a great paper he has written, this is probably the key diagram :
'dispersions' here meaning : how wrong can you be about where you will land ? I think the clue to using a single engine for final/landing burns is hinted too ( my red emphasis ):
Which I interpret as needing a lowest thrust option for the last bit of descent ie. better finesse on total thrust to weight. Of course that is only one strategy, which in turn would depend ( at least ) upon what are the dynamic responses of Merlin engines to throttle changes ..... plus what is worse ? A hard landing under power or a dead drop from some height ? I think it is clear that SpaceX has been exploring the 'hard landing under power' parameter space. :-)))
Cheers, Mike.
( edit ) The Dragon was given bad nav data and docking is delayed. " a 'racetrack' trajectory in front of, above and behind the station " presumably refers to a sequence of positions relative to the ISS ie. a prograde burn to go high & slow and later come in under ( nearer to Earth ).
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
Someone over at the
)
Someone over at the NasaSpaceflight.com site has posted the link to this YouTube video from flight club. It appears to be an assemblage of screens, some directly using available video of the flight, while others are calculated from sources I don't know and with accuracy for which I cannot vouch.
Nevertheless I find the altitude and velocity readouts and profiles for the first stage intriguing and plausible. In particular it's worth noticing how much velocity the first stage picks up descending from the post boost back peak to the reentry burn just before meaningful atmospheric drag begins. It is also interesting to see how very quickly after the end of the reentry burn you can see the deceleration from simple aerodynamics cut in.