Engines Over 100%

[Corona688]

I have an ancient memory from a televised space shuttle launch where I overheard them set main engines to over 100% and someone explained how the engines were rated for that for a short period of time.  I also noticed the KSP throttle has markings over 100%, potentially up to 125%.

Is it possible to have engines that go up to 125%, or is this purely decorative?  Or has this been made redundant now by the 'thrust limiter' setting on engines?

[Van Disaster]

The shuttle's main engines went to 104% of the original certified max thrust thanks to upgrades & whathaveyou. Presumably they just didn't want to fully recertify it... someone will probably be along with the details of that.

I'm kinda interested in the redzone for throttle too, hadn't really looked at that before - maybe it was intended for afterburning engines.

[Gaarst]

Engines are designed for a given thrust. The SSMEs were designed to give out 2090kN of thrust in vaccuum, that's 100% of the nominal power.

Now, after quite a few flights, the engineers had collected enough data to realise that the SSMEs were strong enough to get pushed further, to 2170kN, without any risk for the duration of a flight, and that this enabled greater payloads. The launch sequence was modified so that the SSME now used the 2170kN of thrust, of 104.5% of their original maximal thrust. Instead of setting the 2170kN to be 100% and confuse everyone and probably cause one or two shuttle losses (space disasters often happen for pretty stupid reasons), they kept the original 100% and wrote down 104.5% for the launch sequence.

Throttling the SSMEs to 104.5% became part of the nominal launch procedure because it was safe. The engines could be pushed even further (remember that to increase the thrust of the rocket engine, you just need to increase the propellant flow), up to 2280kN, or 109% of the nominal thrust. But this was dangerous: as the engines were not designed to sustain that much thrust, it could damage them and cause the loss of a mission, so the 109% throttle was not used for nominal flights, but kept for emergency procedures.

Back to KSP: having more than 100% throttle in KSP would make no sense. Since engines are essentially perfect and never fail, adding a failure possibility when going past 100% would feel a little strange. If KSP had part failures, then this would be great but just having engines failing when pushed too hard, meh.

A mod increasing the maximal throttle limit past 100% and adding a failure probability should not be to hard to make.

Edited July 18, 2016 by Gaarst