How The Space Shuttle Started Its Engines And Launched

During the last 10 seconds before launch the Space Shuttle performed thousands to operations to turn on the engines, safely bring them to speed and leave the launch pad. There's dozens of engineering cameras which tracked these operations, and they make for amazing viewing. I used this footage to lay out the operations and explain everything that's happening during this amazingly complex choreographed set of operations that are needed to get the Shuttle off the pad and on its way to space.

Based on Footage from this video produced by NASA

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Intro & Outro by Concodroid

[ThitutUhthalye]

These launch videos are such eyes candies. It’s interesting to see all those exhaust plume and smoke travelling in slow motion — to see it travels in orderly way as opposed to the powerful chaotic turbulence we would see in the real time footages.

[nikolamarko]

The fact that only ten seconds of launch it-self can be expanded in information packed eleven minutes and STILL be highly simplified, is testament of complexity of this whole situation :D

[RCAvhstape]

That shot of the engine bell wiggling back and forth between oval shape and round at 6:55 always amazed me; the pure power and fury of what was happening to that big piece of metal was astonishing. Watching live shuttle launches was a thrill that never got old. The engine startup was like a shot of adrenaline.

[rzero]

11 minutes to explain 10 seconds. This is quality content.
Also, Space Shuttle is still the coolest spacecraft ever.

[armyto]

Great explanation of the startup process, Scott. I was the Quality Assurance Manager for the Solid Rocket Boosters and External Tank processing as well as processing of the entire vehicle once rolled out to the Pad. I started as an inspector working on all those systems with operations and engineering. I spent 29 years out there and loved every minute of it. Keep up the great work!

[CatmanFS]

Explaining the white pressure threshold with the ambient air was outstanding. It's comforting to know that there are people out there that actually understand these things and can explain them so clearly for the rest of us. Thanks Scott!

[Stephan]

I always loved watching it launch. It looked so powerful. Especially in slow motion. And the sounds!! Never been to a launch but there are a few great videos with awesome sounds here on YouTube.

[artysanmobile]

Scott, you have simply outdone yourself with this one. I have watched this astounding sequence at least a dozen times in complete awe that such a document can even exist, never mind be of impeccable photographic quality. No living thing could survive a millisecond of the conditions extant at any point past ignition, yet our eyes are present, focused, and aperture-adapted to perfection in multiple locations for the entire process. As the hold-down bolts’ charges explode and 6 million pounds literally leaps off the stand with flawless alignment, I am reminded that essentially, I am witnessing the impossible.

[msudawg]

The first SSME live firing I saw was on my first day working for Rocketdyne at Stennis. I remember being in awe of the power as I watched the test from only 1/4 mile away. I witnessed (and eventually ran) a lot of SSME tests in the years following that day. By far the most fun I've had in my 25 year career.

[dandeprop]

Hi Scott--Very nicely done. I'd like to add a few things that I hope you might find helpful--Regarding the preburner oxidizer valve opening profiles (OPOV and FPOV) the 'dipsy-doodle' nature of these is because of the nature of the initial hydrogen flow into the preburners (especially the Fuel Preburner). When the Start begins, the Main Fuel Valve is ramped open at (essentially) max rate. This causes the downstream fuel lines (the 'steer horns' on the nozzle extension) as well as the nozzle tubes to be 'filled' with hydrogen. The nozzle extension is made from 1080 stainless steel tubes of about 1/4 inch basic diameter each. A VERY high quality heat exchanger! For the next 2 - 2.5 seconds, the fuel system feeding the preburners 'chugs' at its first natural frequency (about 2 Hertz) as that system tries to achieve thermal equilibrium. The hydrogen supply pressure to the preburners oscillates during this period at something like 80 psi 'peak-to-peak'. The 2 high pressure turbines have very strict temperature limits, therefore the mixture ratio going into each preburner has to be 'controlled' (quotes because it isn't really 'controlled'--all of this stuff is open-loop) to keep temperatures from getting out of hand. The opening profile on the FPOV (especially) does what it does to attempt to keep the incoming LOX flow 'in sync' with the oscillating fuel flow. We should make note that it doesn't always work--the start of an SSME is not 'deterministic' as such. We still get temperature spikes in the fuel preburner--we've had some as high as 4000 deg R. Some occur in the Oxidizer Preburner also--STS-68 was an example of such. It takes about 2-and-a-half seconds for this situation to sort itself out. Also note that in some cases (around 5% of the time) the oscillating fuel pressure just doesn't happen--no one knows why. The preburner valve profiles then had to be modified again so that the engine would start acceptably well in either case. Note that the Fuel Preburner is intended to 'start' at Start Command + 1.4 seconds. The Main Combustion Chamber is intended to 'start' at Start Command + 1.5 seconds. This brings up fuel pump turbine 'back pressure' and prevents overspeed. The Oxidizer Preburner is intended to 'start' at Start Command + 1.6 seconds, although that is not as critical as the relation of Fuel Preburner-to-Main Chamber 'start'. This sequencing changed a bit with incorporation of the Pratt & Whitney turbopumps, but for the configuration of the engine you show, and the start sequence plot you show, those are the numbers. Thank you very much.

[FranLab]

Well done Scott. I do wish that SpaceX and NASA would use photochemical high speed cameras on their future launches, but I doubt that will ever happen.

[MoonWeasel]

And those beautiful RS-25s will now be on a one way trip to the bottom of the Atlantic. Hopefully they get the coverage they deserve with 4K video during the launch and start up.

[mcspikes]

This video answered a ton of questions I have always had regarding different aspects of a launch. Thank You.

[genelomas]

That is SO cool..

I've seen snippets of this footage for many years.. but to have your expert analysis commentary over the top makes it all the more awesome.. :)

Thanks Scott 👍

[damienknapman]

I always liked the description of the SRBs as "when those ignited, the question wasn't whether you were going to space, but how much of Florida you were taking with you"

[blckmesa]

The sound of the space shuttle starting is amazing, and those blue cones forming in the exhaust seem almost magical.

[normkirkland]

I'm 70 years old and had just graduated from HS when we first landed on the moon. The Space Shuttle program that followed was a fascinating extension of our space-going program. This video answers some questions I had about the Shuttle launch technology. In particular, the ROFIs. I had assumed all these years that they were what actually ignited the Shuttle engines on launch. Interesting to learn they actually combusted stray hydrogen molecules for safety reasons. Never too old to learn (and appreciate), I guess.

[hoghogwild]

The engines are splayed into the "start" position not only to prevent the engine bells from colliding, but also as a thrust alleviation as the twang loads are applied to the stack. Engine 2 and 3 are gimballed away from each other in the start position, then move together for the liftoff position. If the engines started in their liftoff position, yes the engine bells would be in more danger of collision during startup, while at the same time increasing the twang loads applied to the stack during startup prior to launch. We have to remember that all these off center thrust loads are translated via the SRB field joints. SLS will not have to deal with these "twang" loads that STS did. A few days before launch, the SLS stack will be unbolted from the Mobile Launcher. Since there are no twang loads from the SLS stack, no T minus Zero pyros are need to release the stack from the ML/MLP. In STS days there were 4 frangible nuts that held each SRB to the ML/MLP(Mobile Launcher Apollo and Space Launch System/Mobile Launcher Platform=Shuttle=Space Transportation system. These nuts were detonated via 2 redundant NSD's(NASA Standard Detonators) per nut, 4 nuts per SRB 8 nuts per stack. These charges were initiated along with the SRB T minus Zero signals which lit the starting charges at the top of each SRB. These charges cause a flame front along the entire inner surface of the SRB propellant face. Varying the exact inner shape of the solid propellant allows a certain amount of "throttling" to occur. When the 3 Space Shuttle Main Engines which supply just 1.2 million pounds of thrust at liftoff while the 2 SRBs provide 6.4 million pounds of thrust at liftoff throttle down from just over 6 million pounds thrust down to 4.4 million pounds thrust just before entering the area of maximum dynamic pressure(MAXQ), the SSMEs reduce from 104.5% rated power level down to 67-72%RPL, while at the same time the SRBs thrust decreases thus allowing the Shuttle stack to not crush itself like an aluminum can as it accelerates into the supersonic regime of flight. Following MaxQ, the 3 SSMEs go throttle back up to 104.5% and the SRBs thrust increases up to 5 million pounds thrust. The RSRMV(Redesigned Solid Rocket Motor V=five for 5 segment motor) will have 4 RS25 engines that have actually flown on many Shuttle missions already. The quartet will thrust at 109% RPL, while the new 5 segment RSRMV's will thrust with approx. 4 million x 2 pounds force thrust off the pad. While there have been 5-6 tests of a 5 segment RSRM or FSB Five Segment Booster, they have all been horizontal and have never been fired in the vertical launch position.

[joelongjr.]

I always love to watch a Shuttle launch sequence, especially starting at T-9:00. The call at T-0:31 go for auto sequence start still puts shivers down my spine.

[gafoot]

About the covers over the thrusters, neat story- they originally wanted to use Teflon plugs to cover them in order to prevent rainwater accumulation that could freeze during ascent. They decided to use butcher paper instead since it was lightweight, commercially available (ask your local butcher!), it would easily dislodge during the first thruster firing, and above all, it stopped water from entering the thruster nozzles. After STS-107 they switched to Tyvek covers, since I guess they were finding chunks of paper in the window seals (which probably gave the engineers nightmares!). The newer nose thruster seals had parachutes which caused them to detach in a more predictable manner during ascent (usually as the Shuttle cleared the tower).

(Watching those bursting thruster covers during this video also gives me a clear indication of what would happen to your eardrums if you were there during SSME ignition...). Thanks for posting this video, Scott!