Blue Origin's BE-4 Engine

[DrHeywoodFloyd]

Just dropped a hint they will be testing production BE-4 engines at the MSFC Test Stand 5670 soon!

I hate to dash your hopes, but the "This is BE-4" video that came from is several months old:

No you are not, with respect to your youtube video... I am just reporting the fact of their statement made by their what the commutator just stated during their June 7 Live Broadcast: Vulcan Cert-1 Flight Readiness Firing (FRF) broadcast.... they would not make that statement unless there is clear intent to make it happen...

[DrHeywoodFloyd]

Tory's Happy with the FRF...

https://twitter.com/torybruno/status/1666617678025596928?s=20

Although I am confused, as I thought the test would run longer....but if Tory and Jeff are happy, then so am I!

[Robert_the_Doll]

Replay of the engines firing off, huge win for ULA, Blue Origin, Vulcan, and by extension, New Glenn:
https://twitter.com/ulalaunch/status/1666619621724794881

[Robotbeat]

Presumably for the same reason Starship’s static fire was so short. It’s being tested on its launch mount, not a specialized test stand built for >minute-long firings.

[Robert_the_Doll]

And this from spaceflightnow.com earlier today...
it was a planned six second test....

https://spaceflightnow.com/2023/06/07/vulcan-centaur-frf-coverage/#:~:text=The%20twin%20engines%20will%20flash,flame%20trench%20at%20pad%2041

Yet, why was the test so short [six seconds, I thought something had failed], any ideas?

There is no mystery as originally Tory Bruno said it would last 3.5 seconds and then later it was moved up to 6.5 seconds, presumably to test the BECO throttle down and cutoff test objective rather than do just a straight up pad abort cutoff. All seems to have happened in the latter plan.

Also, the pad was not designed for sustained firing and it could be damaged, even when the engines were throttled down.

The longest such test on a launch pad I know of is the Antares 100 and 200 tests of ~30 seconds duration. But those were much smaller rockets and less powerful engines.

[Robotbeat]

And this from spaceflightnow.com earlier today...
it was a planned six second test....

https://spaceflightnow.com/2023/06/07/vulcan-centaur-frf-coverage/#:~:text=The%20twin%20engines%20will%20flash,flame%20trench%20at%20pad%2041

Yet, why was the test so short [six seconds, I thought something had failed], any ideas?

There is no mystery as originally Tory Bruno said it would last 3.5 seconds and then later it was moved up to 6.5 seconds, presumably to test the BECO throttle down and cutoff test objective rather than do just a straight up pad abort cutoff. All seems to have happened in the latter plan.

Also, the pad was not designed for sustained firing and it could be damaged, even when the engines were throttled down.

The longest such test on a launch pad I know of is the Antares 100 and 200 tests of ~30 seconds duration. But those were much smaller rockets and less powerful engines.

I wouldn't say the were MUCH smaller and less powerful. Vulcan uses 2 BE-4s, Antares used 2 NK-33s or 2 RD-181s.

BE-4 has 550lbf thrust each, RD-181 432lbf thrust, and NK-33 367lbf of thrust. Pretty comparable. (And I think people often under-estimate Antares for some reason. Having ~80% of the thrust of single stick Vulcan and about the same as Atlas V is not so bad. It's a pretty big rocket given there are so many truly small rockets recently developed, from LauncherOne, Electron, Astra's rockets, Terran-R, Firefly, ABL's RS1, etc.)

[FutureSpaceTourist]

[JCRM]

Sparklers? Does this mean Vulcan won't set fire to itself before launch?

Shame.

[Zed_Noir]

Sparklers? Does this mean Vulcan won't set fire to itself before launch?

Shame.

There wasn't any Hydrogen involved. So no self-immolation. 

[catdlr]

Sparklers? Does this mean Vulcan won't set fire to itself before launch?

Shame.

That's why they painted a flame on the stage.  (They should have done that to Delta IV Heavy).

[JCRM]

Sparklers? Does this mean Vulcan won't set fire to itself before launch?

Shame.

There wasn't any Hydrogen involved. So no self-immolation. 

I'm pretty sure methane can catch fire too

[lightleviathan]

ULA probably saw Starship and didn't want to repeat that.

[Jim]

Sparklers? Does this mean Vulcan won't set fire to itself before launch?

Shame.

Delta IV used ROFIs too

[Jim]

There wasn't any Hydrogen involved. So no self-immolation. 

Methane is also lighter than air

[Zed_Noir]

There wasn't any Hydrogen involved. So no self-immolation. 

Methane is also lighter than air

Was thinking of the cloud of Hydrogen that seeps out and halo Delta IV CBC during propellant loading. Presuming the Vulcan Centaur will have a more control release of Methane to drastically reduces the chances of a Delta IV style self-immolation spectacle during lift off.

[Jim]

There wasn't any Hydrogen involved. So no self-immolation. 

Methane is also lighter than air

Was thinking of the cloud of Hydrogen that seeps out and halo Delta IV CBC during propellant loading.

the hydrogen comes from engine start sequence

[lrk]

Note that the large pre-ignition fuel bleed is something specific to the RS-68; this isn't seen even with other LH2-burning engines like RS-25 on the shuttle/SLS.  Generally dumping a lot of fuel prior to engine start is something preferable to avoid - there were some studies done on eliminating the fireball entirely if Delta was to be human-rated.

In general it is better to start a rocket engine fuel-rich to avoid damage during startup transients, but I've never got a clear answer on why RS-68 releases so much more fuel on startup than other engines. 

[edzieba]

IIRC, the RS-68 generates a 'fireball' because it's a gas-gen engine (unusual for hydrolox) with a conservative start sequence. That means plenty of Hydrogen-rich exhaust is dumped outboard before the MCC really starts getting going (after which any GG exhaust is entraining along with the surrounding air down into the flame duct), and Hydrogen has a very wide range of flammability (4-75% in air) so you can either burn it in a controlled manner, or it will burn itself in an uncontrolled manner.
The BE-4 is a full-flow engine so has no fuel-rich (or oxidiser-rich) gas gen exhaust to dump, Methane has a relatively narrow range of flammability in air (5-17% in air), and BE-4 appears to have a relatively rapid startup sequence (maybe even sub-second from main valves opening).
The ROFIs for Vulcan seem more a "we've always done it, we have then on hand, so why risk the tiny chance of an issue with a Methane leak?" belt & braces approach rather than the necessity of them for normal operation as on Delta IV.

[Robert_the_Doll]

ULA probably saw Starship and didn't want to repeat that.

Very unlikely. Methane's flammability is well-understood and there was considerable work done with the PTT core and the BE-4 engines mounted on it that would have allowed them to understand how much of the gas builds up under the pad during a typical countdown.

[Jim]

The ROFIs for Vulcan seem more a "we've always done it, we have then on hand, so why risk the tiny chance of an issue with a Methane leak?" belt & braces approach rather than the necessity of them for normal operation as on Delta IV.

or it could be more for a shutdown sequence