FAILURE: Sea Launch - Intelsat 27 - February 1, 2013 (0656UTC)

[ugordan]

I was told that there was not 100% thrust of engine at rocket liftoff.

If that's the case, it's a really "nice" feature - to have the vehicle issue a launch commit command even though its propulsion system didn't satisfy nominal operation criteria. I find that a little hard to believe.

Have to agree with that. If the system allows the vehicle to lift off under these circumstances, then there's something seriously wrong with the system.

IIRC the RD-171 cannot shutdown once a preliminary thrust level is reached (I think there was some kind of a membrane that has to be broken near the fuel inlet at ignition, and there was a SL Zenit launch that was aborted just after ignition at the request of the spacecraft controller, and as the process is irreversible the whole team had to set sail back to Long Beach to replace the first stage engine - am I correct?)....

The story was that it had to be refitted after the aborted ignition, but that's an irrelevant point. A new/refitted engine required still costs less than a new engine + new rest of the vehicle + new satellite.

[Proponent]

IIRC the RD-171 cannot shutdown once a preliminary thrust level is reached (I think there was some kind of a membrane that has to be broken near the fuel inlet at ignition, and there was a SL Zenit launch that was aborted just after ignition at the request of the spacecraft controller, and as the process is irreversible the whole team had to set sail back to Long Beach to replace the first stage engine - am I correct?)....

So are you saying that it is possible to shut an RD-171 after ignition, but then the engine must be replaced?

[Proponent]

Do we know whether Zenit actually has hold-down following ignition?  I thought the usual Russian practice was to ignite at a low thrust level without hold-down, have a quick look to see whether things are OK, and then throttle up and go.

[Antares]

All rocket motors have a potential communality. So you need to go to start the trebuchet.

Ugh.  Wrong.  Don't post pointless stuff.

[ugordan]

Do we know whether Zenit actually has hold-down following ignition?  I thought the usual Russian practice was to ignite at a low thrust level without hold-down, have a quick look to see whether things are OK, and then throttle up and go.

Observe pyros firing right at start of video.

[360-180]

"Двигатель отработал абсолютно штатно, штатно произведен пуск, штатно отработал 20 секунд, штатно отключился по сигналу системы аварийного выключения двигателя. Именно штатно, без каких-либо замечаний", - сказал "Интерфаксу-АВН" в пятницу руководитель предприятия - исполнительный директор НПО "Энергомаш" Владимир Солнцев.
"К двигателю претензий нет. Это 100% гарантия", - добавил он.

'The engine is absolutely nominally worked' - said the executive director of the NGO "Energomash" Vladimir Solntsev

Edit by mod: Already quoted earlier in this thread

[Gary NASA]

I'm viewing the multi-angle launch videos in L2, including from the pad, of the Sea Launch failure with NSS-8 and and that one launched for a second or so before losing all thrust and falling through the pad.

This one must have had most of its thrust to get off there.

[Proponent]

Any chance those pyros serve the purpose of holding the rocket steady before launch (e.g., against swells), but aren't meant to hold the rocket down at full thrust?  I'm just wondering, because the Shuttle had pyros too, but once the SRBs lit up, the vehicle was going somewhere.

[Danderman]

Russian launch pads typically use a counterweight system that allows liftoff when the engine thrust can offset the counterweight.

[douglas100]

IIRC the RD-171 cannot shutdown once a preliminary thrust level is reached (I think there was some kind of a membrane that has to be broken near the fuel inlet at ignition, and there was a SL Zenit launch that was aborted just after ignition at the request of the spacecraft controller, and as the process is irreversible the whole team had to set sail back to Long Beach to replace the first stage engine - am I correct?)....

If you're talking about the XM-1 abort on January 8  2001, then it seems that the engine began its start sequence but had not actually ignited. And yes, it had to be replaced.

http://spaceflightnow.com/sealaunch/xm1/010108abort_qt.html

Still don't know if it's possible to shut down the RD-171 after ignition, but before the clamps are released for lift off.

[pippin]

IIRC the RD-171 cannot shutdown once a preliminary thrust level is reached

Um. Maybe not without the requiring some servicing, replacement, whatever. But it really looks a lot like it DID get shutdown in this case after reaching preliminary thrust level.

And saving a payload should really be worth the hassle.

[pippin]

Umm... And could some of you please stop generalizing what R7 does to "Russians typically....". They've got more than one solution, too.

[douglas100]

Russian launch pads typically use a counterweight system that allows liftoff when the engine thrust can offset the counterweight.

True for Soyuz, not sure about other vehicles.

[smoliarm]

Does [winds: 6 knots & seas: 6.5’] qualify as “rough sea” ??
6 knots translates into 3.1 m/sec – it’s almost nothing, as I understand – am I right?
seas: 6.5’ – 2 meter waves; can they make an ocean oil rig “unstable” ??

As a 20 year US Navy vet, I will state unequivocably that 6 knot winds and 6.5ft seas are nothing to a vessel the size of the Odyssey platform, particularly when it is ballasted down for launch.  In addition, such platforms usually have some form of active stabilisation.

They're not going to be able to blame this one on the local weather conditions (JMNSHO, of course).

Thanks a lot, that's exactly what I need to know.

[360-180]

Russian launch pads typically use a counterweight system that allows liftoff when the engine thrust can offset the counterweight.

LV Zenit launch pad uses explosive bolts to hold

[ugordan]

This one must have had most of its thrust to get off there.

True, but consider also that it could have gotten off of there with significantly less than full thrust, too. RD-171 provides for a T/W ratio at liftoff in excess of 1.5, similar to U.S. SRB-assisted liftoffs.

Not that this liftoff looked particularly slow or sluggish, it looked about right for a Zenit to my (untrained) eye.

[Chris Bergin]

Yeah, for the quality of the stream (not at all great), the initial ascent didn't strike me as odd.

[smoliarm]

Some basic rocketry question: since the RD-171 is a four thrust chamber engine, does it mean that if one (or lets say two) of them have developed leakage due to nozzle/thrust chamber damage, the others can still function properly? Would it have affected engine gimballing as well?

AFAIK, RD-171 is a SINGLE engine, and a failure of any thrust chamber results in shutdown of the whole thing. 

[Mapperuo]

Watching it side by side the Intelsat 21 Zenit, also a night launch, bar the pitching it's pretty similar to my eye.

[ugordan]

AFAIK, RD-171 is a SINGLE engine, and a failure of any thrust chamber results in shutdown of the whole thing. 

Failure is a broad term. GP talked about a chamber leak. If such a leak doesn't affect vehicle control authority, doesn't burn through some other critical engine component, I say leave the engine running. You gain nothing in an unmanned launch by shutting such an engine down. Last Delta IV didn't shut down its RL-10 either.