This is more or less the crucial section of the upper atmosphere phase after the payload is powering onwards and upwards :
the forward KE has been bled by sheer rocket grunt in 'thin air' and operating hot end first ie. most of the flame burn on the side of the barrel will come from this part. Imagine if you ran forwards with a flamethrower at 1.5 km/sec ! The descent through the thick stuff is about to begin, here the paddles will take up their important braking mode, literally converting KE to paddle heat and air turbulence while hypersonic. It will speed up even while this 'ablation' is occurring, and an even higher speed would result otherwise. Hence a further burn is required in the lower third of the descent 'cliff' to tame that and bring it to a 'mere' couple of hundred metres per second. Only as fast as a speeding bullet ! Then finally the terminal burn to a gentle touchdown at a handful of metres/sec. The power finesse to perform here is available across that range of conditions by choosing how many* engines of the nine to re-light and the deep throttling capacity of each. Legend ! :-)
I would emphasise that no one else is either doing or has done this. The Space Shuttle had to 'surf' across the upper atmosphere from New Zealand to California, unpowered, to bleed it's massive KE. Every manoeuvre costs something that has to be carefully accounted for in design. Even with ICBM's the pointy end only had to survive long enough to reach ignition point for the fusion device within.
Cheers, Mike.
* Indeed I would like to know which were operating during those powered portions.
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
Well done ! I've pinched the graphic to my personal hosting :
... consider plus one gee as free fall ( if I have the sense correct ), so less than that ( including negative numbers ) is due to drag and/or powered thrust. So for a vehicle that size these are serious dynamic adjustments. :-)
If you find using time points annoying, you can still estimate ( average ) acceleration a over some travelled distance s by :
v^2 - u^2 = 2 * a * s
where u is the speed at the beginning of that distance segment and v is the speed at the end. For the near vertical cliff segment - burn2 especially - you could take altitude differences as s because there's relatively not much lateral adjustment.
{ BTW : the above formula is simply derived by conservation of energy. Kinetic energy differences ( the left side multiplied by m/2 ) must equal the nett force applied over the distance s ( which is the right side multiplied by m/2 ). Of course the mass is changing .... so there is much ready reckoning happening here. }
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
Wow! There IS a whole lot going on behind the scenes. The reentry in that video looked like the meteor that burned over Russia a couple of years ago blowing out windows and sending out a pretty good "thud". Fantastic video tracking. It hard to believe that anything could survive that. I am assuming it did. Or did I miss something.
Stunning footage. Note the right side temperature scale was 2000+, probably scaled as Rankine would be about right ( that would give ~ 1200K for the engine components ).
There were two launches that month, AsiaSat-6 on the 5th and then CRS-4 on the 21st. AsiaSat was a GSTO throw so the boost stage was merely let go down range. I think this is CRS-4 which explains the NASA tracking. The boost descended intact and landed in a well controlled fashion but into the ocean ( there is a video somewhere looking down the barrel as it gently contacts the waves ). It had no legs on it and no barge to catch it anyway.
For SpaceX everything is a test. As I've said : no-one else is anywhere near their expertise at the present. These are high performance hot-rods. If they were public I'd find $20K and invest ! :-)
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
This is more or less the
)
This is more or less the crucial section of the upper atmosphere phase after the payload is powering onwards and upwards :
the forward KE has been bled by sheer rocket grunt in 'thin air' and operating hot end first ie. most of the flame burn on the side of the barrel will come from this part. Imagine if you ran forwards with a flamethrower at 1.5 km/sec ! The descent through the thick stuff is about to begin, here the paddles will take up their important braking mode, literally converting KE to paddle heat and air turbulence while hypersonic. It will speed up even while this 'ablation' is occurring, and an even higher speed would result otherwise. Hence a further burn is required in the lower third of the descent 'cliff' to tame that and bring it to a 'mere' couple of hundred metres per second. Only as fast as a speeding bullet ! Then finally the terminal burn to a gentle touchdown at a handful of metres/sec. The power finesse to perform here is available across that range of conditions by choosing how many* engines of the nine to re-light and the deep throttling capacity of each. Legend ! :-)
I would emphasise that no one else is either doing or has done this. The Space Shuttle had to 'surf' across the upper atmosphere from New Zealand to California, unpowered, to bleed it's massive KE. Every manoeuvre costs something that has to be carefully accounted for in design. Even with ICBM's the pointy end only had to survive long enough to reach ignition point for the fusion device within.
Cheers, Mike.
* Indeed I would like to know which were operating during those powered portions.
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
RE: * Indeed I would like
)
I thought i'd do some calcs (back of beer-mat stylee)
I picked some key points, 20s before First stage shutoff as that is bound to be at full throttle, the rest at start and end of burns.
V and T taken from the video
dV and dT (delta T and delta V) calculated
G = dV/dT/9.8
I haven't worked out how to do google drive and inline images.
So a link will do Calculated Forces
The red numbers are deceleration, it pulls some mighty G for a large structure on the two re-entry burns.
Well done ! I've pinched the
)
Well done ! I've pinched the graphic to my personal hosting :
... consider plus one gee as free fall ( if I have the sense correct ), so less than that ( including negative numbers ) is due to drag and/or powered thrust. So for a vehicle that size these are serious dynamic adjustments. :-)
If you find using time points annoying, you can still estimate ( average ) acceleration a over some travelled distance s by :
v^2 - u^2 = 2 * a * s
where u is the speed at the beginning of that distance segment and v is the speed at the end. For the near vertical cliff segment - burn2 especially - you could take altitude differences as s because there's relatively not much lateral adjustment.
{ BTW : the above formula is simply derived by conservation of energy. Kinetic energy differences ( the left side multiplied by m/2 ) must equal the nett force applied over the distance s ( which is the right side multiplied by m/2 ). Of course the mass is changing .... so there is much ready reckoning happening here. }
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
RE: I thought i'd do some
)
Are they more accurate than how Arthur Dent found his cave in Islington?
David
Miserable old git
Patiently waiting for the asteroid with my name on it.
RE: Are they more accurate
)
Yes, give or take a million years.
Russia launches from new
)
Russia launches from new spaceport.
I was wondering why the
)
I was wondering why the landing stopped and started the engines a couple of times high up... they've been testing stuff up there.
Arstechnica - Can SpaceX really land on Mars? with an intersting video of the Falcon 9 descent in September, 2014.
RE: I was wondering why the
)
Wow! There IS a whole lot going on behind the scenes. The reentry in that video looked like the meteor that burned over Russia a couple of years ago blowing out windows and sending out a pretty good "thud". Fantastic video tracking. It hard to believe that anything could survive that. I am assuming it did. Or did I miss something.
Stunning footage. Note the
)
Stunning footage. Note the right side temperature scale was 2000+, probably scaled as Rankine would be about right ( that would give ~ 1200K for the engine components ).
There were two launches that month, AsiaSat-6 on the 5th and then CRS-4 on the 21st. AsiaSat was a GSTO throw so the boost stage was merely let go down range. I think this is CRS-4 which explains the NASA tracking. The boost descended intact and landed in a well controlled fashion but into the ocean ( there is a video somewhere looking down the barrel as it gently contacts the waves ). It had no legs on it and no barge to catch it anyway.
For SpaceX everything is a test. As I've said : no-one else is anywhere near their expertise at the present. These are high performance hot-rods. If they were public I'd find $20K and invest ! :-)
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
RE: These are high
)
There is a lot to be said for not having stock holders. You only have to please yourself - your schedule your objectives.