Space Shuttle Main Engine (SSME) Startup Sequence

[nightwriterou812]

One badass video. Thanks!

[berndpfe]

Fascinating is the startup phase of the main engines. Those function very alike to a bunsen-burner, supplied by hydrogen and oxygen. First, there is an 'amorphous' flame (thicker mix phase for safe startup of the engine to ensure safe ignition), then slowly transitioning to the final thinner mix for optimal burning characteristics while increasing the supply pressures to its maximum. This phase is visible when the white corecone comes out of the center of the nozzles.

[oomblikkies]

Lovely!

[partipilo]

Very nice video. Great audio, thanks for not drowning it out with music.

[astronomicalguy]

Hi, bond10112.

If you're referring to the "big white halo", it is actually created by the exhaust (steam) from the three Space Shuttle Main Engines (SSME). The halo disappears rapidly when the engines are shut down at Main Engine Cut Off (MECO). All of the flashes that you see after MECO are from the aft thrusters positioning the Orbiter for proper separation from the External Tank (ET).

[bond1011]

Whats all the lights around the ET and the shuttle? Tempature reactions?

[hagfelsh]

I love that you have original audio--what a difference!

[astronomicalguy]

Hi, idan4411.

While I have the unique privilege of knowing the astronauts' email addresses, I'm unfortunately not at liberty to share them with the general public. I can, however, provide you with the following address where you can send any of the astronauts a snail mail:

Astronaut Office/CB

NASA

Johnson Space Center

Houston, TX 77058

[astronomicalguy]

Hi, idan4411.

Truth be known, foam has shed from the external tanks on every flight from day one, so no ... the early Hypalon paint did little, if anything, to prevent foam loss. And, it might be a moot point for the Shuttle Program, but the lessons learned in this area of technology will be applied to future systems that use it.

[idan4411]

...eliminating the TPS tile strikes? this, of course, might just be a moot point since there's only one shuttle mission left.

2. if i have no media credentials, but i have a question to ask a specific astronaut (Greg Chamitoff), how do I pose my question to him?

now that i'm actually thinking about my questions, i can't remember more of them. i'll post them as i recall them.

[BrainHemorrhage91]

@idan4411 Hi, as far is I know, the composition of the foam was changed in 1997 (they stopped using a chemical called "Freon"), which made the foam breaking off more easily...

[idan4411]

thanks! i'll just throw out some questions and check back occasionally to see if you've answered.

1. the first couple of shuttle launches had a painted ET but it was determined that the paint wasn't necessary and added unnecessary weight. is it possible that the paint was helping to keep the insulating foam in place, rather than breaking off and possibly hitting the TPS tiles? wouldn't it make sense to paint only the shuttle-side of the ET, sacrificing a little bit of weight, but perhaps...

[astronomicalguy]

Hi, idan4411.

Well, time permitting, I'd be happy to answer more questions that you have. I'm sure that others benefit from the questions that I answer here.

[matrix49A]

@astronomicalguy Maybe silly question but was there any thought given to embedding netting on the outer surface of the tank while applying the foam to provide physical strength to critical sections?

[astronomicalguy]

Hi, matrix49A.

The foam separating from the surface of the ET was rarely the problem. Most of the time, the foam failed in its cross section due to pressure-sensitive voids and a phenomenon known as cryopumping (which I won't explain here). We always cleaned and primed the ETs prior to applying foam, and that was more than sufficient to keep the foam adhered to the aluminum.

[idan4411]

thank you! geez, if i could sit you down and pick your brain, i have about a million questions about the shuttle!

[astronomicalguy]

Hi, idan4411.

It's good to hear that you are pursuing a career that you will love. Best of luck to you in your transition.

Indeed, the orbiter "hangs" off of the ET. It is attached at the forward end of the tank at the bipod fitting and at the aft end of the tank at the LOX and LH2 fittings. The entire stack, of course, is then held to the Mobile Launch Platform (MLP) by eight explosive nuts at the bases of the SRBs.

[idan4411]

i'm going to school to become an auto mechanic, which is something i love doing. While i have you, maybe you could answer this: when the shuttle is on the launch platform, is there anything supporting the orbiter besides the struts on the ET, or is it just "hanging" there?

[astronomicalguy]

Hi, idan4411.

It's never too late to change professions. If you want to be an engineer, then make it happen. I will be be leaving a sixteen-year engineering career next year to embark upon a new career as an anesthetist.

[idan4411]

The spark igniters look like basic hand-held sparklers. And I'm jealous that you got to be a part of the shuttle program. I wanted to go into engineering but "settled" on computer science, which I ended up not liking.

[astronomicalguy]

Hi, idan4411.

Indeed, it is an amazing piece of hardware on which I had the unique privilege of working for many of my years at NASA. I, for one, will miss this program dearly.

[idan4411]

Those are some of the most interesting angles that i've ever seen of a shuttle launch. I've read all about the liftoff sequence, but since so much happens in mere milliseconds that it's difficult to be able to see each component. This video shows exactly that! One thing I especially enjoyed seeing is the water jets of the Sound Suppression System.

[astronomicalguy]

Hi, serialkissersband.

Those devices are called spark igniters. We throw sparks out just prior to engine start to burn off any excess hydrogen that may have accumulated beneath the engine bells during tanking (i.e. filling the big orange tank with propellants) and chill-down. If we didn't do this, we could suffer a hydrogen explosion (bad thing) when the initial burning oxygen/hydrogen mixture exits the nozzle.

[astronomicalguy]

Hi, pesciro.

Your assessment is spot on ... the SRBs carry the weight of the entire Shuttle stack and the hold-down bolts/nuts prevent the vehicle from tipping over -- not only during transport and quiescent pad operations, but during SSME start-up!! The hold-down bolts are 28 inches long and 3.5 inches in diameter. The frangible (explosive) nuts, then, have a threaded (internal) diameter of 3.5 inches.

[astronomicalguy]

The umbilical that you see detach from the ET at 1:47 is the ground umbilical carrier panel (GUCP, pronounced "gup"), attached to the intertank (the empty space between the LO2 and LH2 tanks). This assembly provides ground power and inert gasses during ground operations. It also, most importantly, draws gaseous hydrogen (GH2) off of the top of the LH2 tank as it is being filled. We have to vent this "boil off" or the tank would over-pressurize as it is filling.

[astronomicalguy]

Once the LH2 and LO2 T-0 umbilicals separate, they are pulled into their respective tail-service masts (attached to the MLP), and the tail-service mast doors close to protect the hardware from the pending heat, smoke, and fire as the stack ascends.

[astronomicalguy]

The external tank (ET) is filled from the bottom up through T-0 umbilicals. The umbilical that you see detach at 1:39 into the video is the liquid-hydrogen (LH2) umbilical, and the umbilical that you see detach at 1:43 into the video is the liquid-oxygen (LO2) umbilical. Both of these umbilicals detach at the same time -- T-0!! The fact that they seem staggered in the video is 100% due to video editing (dramatization).

[astronomicalguy]

Hi, tinus80.

Ah ... you're referring to the umbilicals. I'll post separate responses due to the character limitation.

[astronomicalguy]

Hi, tinus80.

The entire Shuttle stack is held to the Mobile Launch Platform (MLP) at the base of each of the two Solid Rocket Boosters (SRB) by eight explosive nuts (four per booster). In my previous post, I referred to these as bolts, but the explosive parts are actually nuts ... really big nuts. They explode just prior to ignition of the SRBs to allow the stack to lift off of the MLP.

[tinus80]

@astronomicalguy, Thanks for the quick reply. I am reffering also to 1:38 till 1:49 of the video. These things, which are quickly released and hidden behind some closing doors... and a hose, which is connected to the fueltank. :)

[pesciro]

@astronomicalguy

So the SRB's carry the weight of the whole stack when on the ground, and what gives extra stability to prevent the vehicle from tipping over are the explosive nuts. Am I right? How big are those nuts?

[tinus80]

What are these clambs for which are releasing?

[astronomicalguy]

Hi, LonghornPhysicist.

Indeed, we are so confident that the Solid Rocket Boosters (SRB) are going to ignite on demand that we release the hold-down bolts prior to 'lighting the candles'. The process of the explosive decomposition of ammonium perchlorate (SRB fuel) is so predictable, and the manufacturing process is so tightly controlled, that we know without a doubt that they will perform as needed every time.

[LonghornPhysicist]

Do they release the hold down clamps before the SRB's start? In this video it looks like they do. If thats so it looks like the whole shuttle stack is just literally sitting on the pad for a few microseconds before those bad boys fire up! Awesome! Yay engineering.

[astronomicalguy]

Hi, pesciro.

That's good thinking, however, there are a couple of different things occurring. The "big white halo" is actually created by the exhaust (steam) from the three Space Shuttle Main Engines (SSME). The halo disappears rapidly when the engines are shut down at Main Engine Cut Off (MECO). All of the flashes that you see after MECO are from the aft thrusters positioning the Orbiter for proper separation from the External Tank (ET).

[pesciro]

@astronomicalguy

Awesome! Thanks a lot!

[pesciro]

Do you know what's that white halo around the vehicle when it pitches to detach from the tank? Is that an aerodynamic effect produced by whatever little atmosphere is up there?

[astronomicalguy]

Hi, McChuugy.

Those devices are called spark igniters. We throw sparks out just prior to engine start to burn off any excess hydrogen that may have accumulated beneath the engine bells during tanking (i.e. filling the big orange tank with propellants) and chill-down. If we didn't do this, we could suffer a hydrogen explosion (bad thing) when the initial burning oxygen/hydrogen mixture exits the nozzle.

[McChuugy]

What are those spark things shooting out?!?!

[EpiDemic117]

to 01z06 guy the dumbass who was smart enough to copy my link and paste it in the address bar. I understand your retardation :D but put forth and simple enough to learn. Space shuttle > your POS Z06.

[24s157]

my god this is amazing

[epicuniversal]

Three minutes and thirty-eight seconds of awesome power :D.

I'm sure going to miss the space shuttle program :(

[astronomicalguy]

It's actually eight and a half minutes of awesome power!!

It's going to suck when she's gone, especially if we don't replace her.

[Jan07191]

Lord, I'm going to miss the Space Shutle. :*(

[Rob260259]

Awesome!

[fyrodimi]

Very nice!!! first time with sound.

[crazybastard82]

that was cool. you don't get to see many vids of the twang. it's amazing the only things keeping the whole stack from tipping over at main engine start are the explosive bolts on the srb skirts.

[markzzxx]

That was wicked bro..

[allcanitbe]

wow!!

[locomike1219]

this really is the coolest compilation video i have yet to see!

[iamhere12345678]

All I can say is "wow". These two videos (see channel) are by far the most detailed and high quality seen here on youtube. I have seen the same old shots now for 19 years that show the liftoff but these camera angles give the viewer the best perspective and show the real power of this spaceship. I wish the live scenes on TV would show this view (perhaps these cameras are not set up for live scenes now). Anyway, a few other videos on youtube show some of this but this is the best of all.