Crew Dragon
- Thread starter neosapien
- Start date
cannabineer
Ursus marijanus
BiglyAnybody else excited about the launch tomorrow? I hope the weather cooperates. I have mixed feelings about Elon Musk most days but he got people excited about space again.
neosapien
Well-Known Member
I feel like a little kid again!!! Lol, I'm so pumped.Bigly
cannabineer
Ursus marijanus
I know! I ate the space program up with a small spoon until I had the cold bucket of water realization that Mercury through Shuttle were basically political enterprises.
uh-HUHuhuh, I said ...
cannabineer
Ursus marijanus
Some say that before the first human crew was approved, there was a test flight that was uhm somewhat crewed.
cannabineer
Ursus marijanus
And the first stage comes back!
I wouldn’t buy a Tesla on a bet, but this ... this is cool.
tyler.durden
Well-Known Member
12 hours away!!! Watch it live...
cannabineer
Ursus marijanus
I draw attention to the second image.
And the first stage comes back!
I wouldn’t buy a Tesla on a bet, but this ... this is cool.
On my phone screen, the downward speed of the exhaust plume near the engine bells is roughly 5mm/sec = 300mm/min.
The rocket is moving up at a barely perceptible rate which we can calculate.
From the camera angle, the rocket is about 1 vehicle length (~70m) above launch position.
Initial vehicle weight is one million pounds, and the nine Merlin 1D engines produce 1.7 million pounds of thrust at sea level.
This gives an initial acceleration of 17 m/sec squared. We cancel ten of those, as the thrust and gravitation vectors are diametrically opposed. So net upward acceleration is 7 m/s2.
A quick over the thumb calculation shows that it takes 5 sec of flight time to reach this altitude. This places vehicle velocity at 35 m/s.
We know that the Merlin 1D has a specific impulse (Isp, a basic property of a given rocket engine design) of 275 sec (if you burn one pound of propellant to produce one pound of thrust, this takes 275 seconds). If you burn 1pound in 1 second, you get 275 pounds thrust. From freshman physics (I = mv) this implies an exhaust velocity of 2700 m/s.
Okay, 2700 m/s in this time-lapse image translates to 5 mm/s on my screen. So 35 divided by 2700 (the dimensions cancel) = 0.013 mm/s or 0.8 mm/min. That is damn close to my ballpark visual estimate of 1mm/min apparent upward velocity.
Physics in real life, bitches!
I wanna give a huge shoutout to my dad (he turns 90 this year and still has a sharp mind) for encouraging and demonstrating to me to work problems like this. It wasn’t until deep into adulthood that I realized that I love this sort of problem-solving. There is a satisfying beauty to having a method and reaching an insight into what’s going on at an engineering level.
Disclaimer. I used very approximate values in the above napkin math. If I were rigorous, I might find that error exceeds calculated value. So there’s no real confidence in the result.
And yet I find the convergence of observed-and-derived value with known and published values to be emotionally satisfying.
Corollary: 850 tons of thrust / 275 seconds = about 3 tons/second fuel consumption. Stage 1 carries about 400 tons of propellant. That calculates to about 130 seconds of burn time.
However the listed burn time is 160 s, which implies that the stage does not burn all engines at full thrust/full duration. Apollo launchers did this by shutting down the center engine at a set time. Falcon does it by keeping all engines lit, but by using a capacity for throttling propellant flow. The profile in the link verified my conclusion.
Flight Profile – Falcon 9 – SES-10
spaceflight101.com
Anyone still awake after my science-teacher siege?
Last edited:
But pchem.I draw attention to the second image.
On my phone screen, the downward speed of the exhaust plume near the engine bells is moving down at roughly 5mm/sec = 300mm/min.
The rocket is moving up at a barely perceptible rate which we can calculate.
From the camera angle, the rocket is about 1 vehicle length (~70m) above launch position.
Initial vehicle weight is one million pounds, and the nine Merlin 1D engines produce 1.7 million pounds of thrust at sea level.
This gives an initial acceleration of 17 m/sec squared. We cancel ten of those, as the thrust and gravitation vectors are diametrically opposed. So net upward acceleration is 7 m/s
A quick over the thumb calculation shows that it takes 5 sec of flight time to reach this altitude. This places vehicle velocity at 35 m/s.
We know that the Merlin 1D has a specific impulse (Isp, a basic property of a given rocket engine design) of 275 sec (if you burn one pound of propellant to produce one pound of thrust, this takes 275 seconds). If you burn 1pound in 1 second, you get 275 pounds thrust. From freshman physics (I = mvthis implies an exhaust velocity of 2700 m/s.
Okay, 2700 m/s in this time-lapse image translates to 5 mm/s on my screen. So 35 divided by 2700 (the dimensions cancel) = 0.013 mm/s or 0.8 mm/min. That is damn close to my ballpark visual estimate of 1mm/min apparent upward velocity.
Physics in real life, bitches!
I wanna give a huge shoutout to my dad (he turns 90 this year and still has a sharp mind) for encouraging and demonstrating to me to work problems like this. It wasn’t until deep into adulthood that I realized that I love this sort of problem-solving. There is a satisfying beauty to having a method and reaching an insight into what’s going on at an engineering level.
Disclaimer. I used very approximate values in the above napkin math. If I were rigorous, I might find that error exceeds calculated value. So there’s no real confidence in the result.
And yet I find the convergence of observed-and-derived value with known and published values to be emotionally satisfying.
Corollary: 850 tons of thrust / 275 seconds = about 3 tons/second fuel consumption. Stage 1 carries about 400 tons of propellant. That calculates to about 130 seconds of burn time.
However the listed burn time is 160 s, which implies that the stage does not burn all engines at full thrust/full duration. Apollo launchers did this by shutting down the center engine at a set time. Falcon does it by keeping all engines lit, but by using a capacity for throttling propellant flow. The profile in the link verified my conclusion.
Flight Profile – Falcon 9 – SES-10
Anyone still awake after my science-teacher siege?
kelly4
Well-Known Member
Yep.I draw attention to the second image.
On my phone screen, the downward speed of the exhaust plume near the engine bells is moving down at roughly 5mm/sec = 300mm/min.
The rocket is moving up at a barely perceptible rate which we can calculate.
From the camera angle, the rocket is about 1 vehicle length (~70m) above launch position.
Initial vehicle weight is one million pounds, and the nine Merlin 1D engines produce 1.7 million pounds of thrust at sea level.
This gives an initial acceleration of 17 m/sec squared. We cancel ten of those, as the thrust and gravitation vectors are diametrically opposed. So net upward acceleration is 7 m/s
A quick over the thumb calculation shows that it takes 5 sec of flight time to reach this altitude. This places vehicle velocity at 35 m/s.
We know that the Merlin 1D has a specific impulse (Isp, a basic property of a given rocket engine design) of 275 sec (if you burn one pound of propellant to produce one pound of thrust, this takes 275 seconds). If you burn 1pound in 1 second, you get 275 pounds thrust. From freshman physics (I = mvthis implies an exhaust velocity of 2700 m/s.
Okay, 2700 m/s in this time-lapse image translates to 5 mm/s on my screen. So 35 divided by 2700 (the dimensions cancel) = 0.013 mm/s or 0.8 mm/min. That is damn close to my ballpark visual estimate of 1mm/min apparent upward velocity.
Physics in real life, bitches!
I wanna give a huge shoutout to my dad (he turns 90 this year and still has a sharp mind) for encouraging and demonstrating to me to work problems like this. It wasn’t until deep into adulthood that I realized that I love this sort of problem-solving. There is a satisfying beauty to having a method and reaching an insight into what’s going on at an engineering level.
Disclaimer. I used very approximate values in the above napkin math. If I were rigorous, I might find that error exceeds calculated value. So there’s no real confidence in the result.
And yet I find the convergence of observed-and-derived value with known and published values to be emotionally satisfying.
Corollary: 850 tons of thrust / 275 seconds = about 3 tons/second fuel consumption. Stage 1 carries about 400 tons of propellant. That calculates to about 130 seconds of burn time.
However the listed burn time is 160 s, which implies that the stage does not burn all engines at full thrust/full duration. Apollo launchers did this by shutting down the center engine at a set time. Falcon does it by keeping all engines lit, but by using a capacity for throttling propellant flow. The profile in the link verified my conclusion.
Flight Profile – Falcon 9 – SES-10
Anyone still awake after my science-teacher siege?
tangerinegreen555
Well-Known Member
I'm not real happy about the weather forecast down there today.
4:33? Confidence is not high.
4:33? Confidence is not high.
cannabineer
Ursus marijanus
The wand chooses the wizard, Harry.
cannabineer
Ursus marijanus
I think the real issue is weather under the Atlantic trajectory. The capsule isn’t rated for storm seas. The recovery vessels need decent sea state as well. So local weather is meh but absence of no-go weather on the whole Atlantic leg is the decider iirc.
tangerinegreen555
Well-Known Member
Singlemalt
Well-Known Member
I don't like the suits, they look like mighty morphin power rangers
raratt
Well-Known Member
Thrust make go fast.I draw attention to the second image.
On my phone screen, the downward speed of the exhaust plume near the engine bells is moving down at roughly 5mm/sec = 300mm/min.
The rocket is moving up at a barely perceptible rate which we can calculate.
From the camera angle, the rocket is about 1 vehicle length (~70m) above launch position.
Initial vehicle weight is one million pounds, and the nine Merlin 1D engines produce 1.7 million pounds of thrust at sea level.
This gives an initial acceleration of 17 m/sec squared. We cancel ten of those, as the thrust and gravitation vectors are diametrically opposed. So net upward acceleration is 7 m/s2.
A quick over the thumb calculation shows that it takes 5 sec of flight time to reach this altitude. This places vehicle velocity at 35 m/s.
We know that the Merlin 1D has a specific impulse (Isp, a basic property of a given rocket engine design) of 275 sec (if you burn one pound of propellant to produce one pound of thrust, this takes 275 seconds). If you burn 1pound in 1 second, you get 275 pounds thrust. From freshman physics (I = mvthis implies an exhaust velocity of 2700 m/s.
Okay, 2700 m/s in this time-lapse image translates to 5 mm/s on my screen. So 35 divided by 2700 (the dimensions cancel) = 0.013 mm/s or 0.8 mm/min. That is damn close to my ballpark visual estimate of 1mm/min apparent upward velocity.
Physics in real life, bitches!
I wanna give a huge shoutout to my dad (he turns 90 this year and still has a sharp mind) for encouraging and demonstrating to me to work problems like this. It wasn’t until deep into adulthood that I realized that I love this sort of problem-solving. There is a satisfying beauty to having a method and reaching an insight into what’s going on at an engineering level.
Disclaimer. I used very approximate values in the above napkin math. If I were rigorous, I might find that error exceeds calculated value. So there’s no real confidence in the result.
And yet I find the convergence of observed-and-derived value with known and published values to be emotionally satisfying.
Corollary: 850 tons of thrust / 275 seconds = about 3 tons/second fuel consumption. Stage 1 carries about 400 tons of propellant. That calculates to about 130 seconds of burn time.
However the listed burn time is 160 s, which implies that the stage does not burn all engines at full thrust/full duration. Apollo launchers did this by shutting down the center engine at a set time. Falcon does it by keeping all engines lit, but by using a capacity for throttling propellant flow. The profile in the link verified my conclusion.
Flight Profile – Falcon 9 – SES-10
Anyone still awake after my science-teacher siege?
jerryb73
Well-Known Member
cannabineer
Ursus marijanus
Considering that a power ranger’s helmet is styled after a predator’s head with the visor as the mouth, I think SpaceX missed a trick. With just a bit of extra styling the helmets could have emulated this majestic beast.
