Space Shuttle Main Engine (SSME) Startup Sequence

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Science & Technology

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• SSMESequence

[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).

[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.

[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.

[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.

[locomike1219]

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

[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.

[bond1011]

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