Stoke Space

[StrandedonEarth]

The problem is the imprecision of the wording. If they said “full mission duration “ or “full planned test duration”, it would save these arguments.

[tater]

19 minutes ago, StrandedonEarth said:

The problem is the imprecision of the wording. If they said “full mission duration “ or “full planned test duration”, it would save these arguments.

Their statements are fine, they know what they are doing better than randos with axes to grind.

[JoeSchmuckatelli]

1 hour ago, tater said:

randos with axes to grind

Aka 'the internet' 

[sevenperforce]

On 6/18/2024 at 1:07 PM, darthgently said:

Yep. Has there ever been a rocket engine test officially tagged a "partial duration test" for example? 

Indeed. A "partial duration" test would be a weird and confusing way of describing a test fire.

Language is descriptive, not prescriptive. But that doesn't mean anything goes. We use language because it is useful for communicating; if a particular use of language fails to communicate, then that use should be deprecated. 

Reminded of this....

Spoiler

If a usage of language is sufficient to communicate the desired information within readily available context, then that is a good use of language. "The rocket engine completed a full-duration test" could mean that the engine completed a test fire equal to the duration of a launch, but it could also mean that the engine completed the full planned duration of the test. That's where you have to look to context. If this claim is accompanied by a video of a 15-second static fire, then context has provided you with all of the necessary supporting information.

On 6/18/2024 at 1:07 PM, darthgently said:

And a "launch duration test" ™️ still doesn't test fuel icing and slosh, ambient pressure changes with altitude, and bird strikes.  For full safety we really need to be doing full bird strike tests of all rocket engines.  Until then every one of them is a ticking timebomb

On 6/18/2024 at 3:44 PM, Exoscientist said:

 If Blue Origin continually referred to their little suborbital hops by New Shepard  as “flights to orbit”, it would then be accepted in the rest of the industry they are flights to orbit. You just have to keep repeating it.

I had a dream last night that I had the chance of getting a seat on a New Shepard launch with Bezos on board, but one of my wife's high school friends ended up taking my place. Bezos had pulled a Musk and decided to launch New Shepard out of the top of a barn for "rule of cool" rather than from the existing launch mount, and the engine clipped the struts of the barn, causing the launch escape system to trigger while still in the building. I simultaneously mourned the loss of my wife's friend and rapidly shorted Amazon stock, making tons of money in the process.

This anecdote has nothing to do with the terms used by SpaceX or Stoke, of course.

On 6/18/2024 at 5:16 PM, magnemoe said:

Agree, now an rocket engine burning for minutes would get kind of dull to watch. Also starting the engine is harder than running it. 
Still why call it full duration burns if its not?

I suppose that we could say there is a difference between a "full duration test fire" and a "full duration test burn". A "test fire" can be any length, while a "test burn" suggests the length of an ascent burn.

"Full duration test" is therefore ambiguous and so reference to a full duration test should be accompanied by additional context clues.

On 6/18/2024 at 8:33 PM, JoeSchmuckatelli said:

I've always assumed that phrase meant 'duration the rocket would be lit during a launch' - so, like, a little over 2 minutes for a Falcon. 

Doesn't that allow them to make sure the engine won't eat itself before stage separation? 

For modern engines that use regenerative cooling, the thermal conditions are really quite extreme. Within a few seconds of startup, the system will reach steady-state operation: all of the heat going into the engine and all of the heat coming out of the engine is in equilibrium. As a rule, rocket engine failures don't happen slowly or gradually; if something is going to go then it goes fast. So achieving complete startup and getting 10 seconds or so of a burn is pretty good evidence that the engine won't eat itself.

[tater]

4 minutes ago, sevenperforce said:

If a usage of language is sufficient to communicate the desired information within readily available context, then that is a good use of language. "The rocket engine completed a full-duration test" could mean that the engine completed a test fire equal to the duration of a launch, but it could also mean that the engine completed the full planned duration of the test. That's where you have to look to context. If this claim is accompanied by a video of a 15-second static fire, then context has provided you with all of the necessary supporting information.

Well said.

4 minutes ago, sevenperforce said:

For modern engines that use regenerative cooling, the thermal conditions are really quite extreme. Within a few seconds of startup, the system will reach steady-state operation: all of the heat going into the engine and all of the heat coming out of the engine is in equilibrium. As a rule, rocket engine failures don't happen slowly or gradually; if something is going to go then it goes fast. So achieving complete startup and getting 10 seconds or so of a burn is pretty good evidence that the engine won't eat itself.

Musk actually addressed elements of this in the recent tour video with Dodd. What you learn from tests vs flying, and what they are interested in characterizing needs flight testing.

[Nuke]

you can never actually simulate the full operating conditions of flight on the ground. no g loads, no pressure changes, no engine next to it blowing up.