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RGClark

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From: Philadelphia, PA

Registered: 2006-07-05

Posts: 765

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A route to aircraft-like reusability for rocket engines.

A route to aircraft-like reusability for rocket engines.
https://exoscientist.blogspot.com/2024/ … ility.html

An interesting discussion on longevity of jet engines:

The question I raise is whether this could also increase the reuse capability of rocket engines.

Near the end I suggest, SpaceX is using this principle of running the engines at lowered power to increase engine life for the purpose of increasing the reliability of the Raptors. If they are, then they should explore the potential of this principle to also extend rocket engine reuse capability.

  Bob Clark

Last edited by RGClark (2024-04-18 23:45:15)

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Old Space rule of acquisition (with a nod to Star Trek - the Next Generation):

      “Anything worth doing is worth doing for a billion dollars.”

tahanson43206

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Registered: 2018-04-27

Posts: 19,408

Re: A route to aircraft-like reusability for rocket engines.

This post is reserved for an index to posts that may be contributed by NewMars members over time.

(th)

kbd512

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Registered: 2015-01-02

Posts: 7,856

Re: A route to aircraft-like reusability for rocket engines.

"On-Wing Time" is the figure of merit for power turbines aboard aircraft, or now, reusable spacecraft.  If maintenance cannot be performed with the engine still attached to the vehicle, then that typically requires major downtime in most cases.  Rocket engines are somewhat unique in that access to the engine is not typically restricted in the same way as a turbofan- there's no engine cowling, no bleed air system, no separate hot section per-se, but the major issues will be the power turbines- the turbopumps that feed gaseous propellant into the engine's main injector plate, the injector pintles, and the electro-hydraulic actuators that gimbal the engine.

Raptor 3 integrates almost all of the engine plumbing into singular 3D printed parts, so seals are limited to the turbopump assemblies.  The individual blades of a pump are what suffers the most.  RS-25s basically trashed those after every flight.  I can't fathom how an engine running at 3X more chamber pressure is any easier on the blades of its pumps.

They need seriously strong metal alloys to work with, hard oxidation resistant aerospace coatings that limit surface erosion damage to the individual turbine blades, and highly capable gas bearing seals.  The rest of the engine needs to be oxidation resistant as well.  I don't know what kind of materials and coatings they use, but they must be bleeding edge to survive in the environment they're being subjected to.

Whether or not they can be made to last as long as a typical turbofan is improbable at best.  You cannot push 100X more power through something smaller than any airliner's engine core and expect those parts to last very long.  RS-25 famously has 280,000shp coursing through a part that you can pick up.  All four screws of the aircraft carriers I served aboard delivered that much power to the water, but the propellers are the size of a house, each one weighs as much as a main battle tank, they're connected to shafts you cannot wrap your arms around, and they operate at very low speed.  Even those power transfer machines will rapidly wear and fail if they're not kept lubricated at all times.  The forces applied to a turbopump in a rocket engine are mind boggling.  They can survive, somehow, but only for a little while, and then they're scrap metal.