Space Things

[Dadhawk]

It's too bad we didn't continue to use and modernize the Saturn V over time, in conjunction with the Shuttle program. To rebuild it now you would basically have to start over since the personnel, rigs, group knowledge, are long gone.

Here's one thing I didn't know until I was reading this article about NASA refiring one of the Saturn V main engines. Just the fuel pump on a main engine produced 31,000 lbs of thrust.

Instead, the team decided to start with a series of firings on F-6049's gas generator. An engine like the F-1 is sort of like two separate rocket engines: one small, one large. The smaller one consumes the same fuel as the larger, but its rocket exhaust is not used to lift the vehicle; instead, it drives the enormous turbopump that draws fuel and oxidizer from the tanks and forces them through the injector plate into the main thrust chamber to be burned.

As with everything else about the F-1, even the gas generator boasts impressive specs. It churns out about 31,000 pounds of thrust (138 kilonewtons), more than an F-16 fighter's engine running at full afterburner, and it was used to drive a turbine that produced 55,000 shaft horsepower. (That's 55,000 horsepower just to run the F-1's fuel and oxidizer pumps—the F-1 itself produced the equivalent of something like 32 million horsepower, though accurately measuring a rocket's thrust at that scale is complicated.)

[shiumai]

It's not the first time older thrusters have been repurposed - here's more insight:


https://www.wired.com/story/nasas-sp...-new-vehicles/

[Dadhawk]

Originally Posted by shiumai

It's not the first time older thrusters have been repurposed - here's more insight:

It doesn't bother me they are repurposing the parts, but taking them from a multi-mission platform to a one and done doesn't make much fiscal sense to me, even if they were mothballed.

[shiumai]

Originally Posted by Dadhawk

It doesn't bother me they are repurposing the parts, but taking them from a multi-mission platform to a one and done doesn't make much fiscal sense to me, even if they were mothballed.

It's a thruster, so there's not much of a difference between one used on a multi-mission platform and a 'one and done'. The R40b has been through multiple space shuttle missions already, so we've got our money's worth out of it. Rather than let it sit unused, it makes fiscal sense to clean it up and put it to good use. I'd be more concerned if they ordered a brand new thruster costing us taxpayers more, when they had some that met the mission requirements in storage.

[Ohio Enthusiast]

Originally Posted by Dadhawk

multi-mission platform

Which required extensive overhaul. It might actually make more economic sense to use them once in the SLS case.

[Spuds]

Originally Posted by shiumai

It's a thruster, so there's not much of a difference between one used on a multi-mission platform and a 'one and done'. The R40b has been through multiple space shuttle missions already, so we've got our money's worth out of it. Rather than let it sit unused, it makes fiscal sense to clean it up and put it to good use. I'd be more concerned if they ordered a brand new thruster costing us taxpayers more, when they had some that met the mission requirements in storage.

Integration of some sub-system into a new super-system can actually cost more than just building a whole new system from scratch. It all depends on how the original system for which that subsystem developed was documented. I can't speak to this case directly, but in general I have found a lot of "tribal knowledge" in legacy systems.

[shiumai]

Originally Posted by Spuds

Integration of some sub-system into a new super-system can actually cost more than just building a whole new system from scratch. It all depends on how the original system for which that subsystem developed was documented. I can't speak to this case directly, but in general I have found a lot of "tribal knowledge" in legacy systems.

Understood and point taken. Here's some info on the particular thruster in the article:
http://www.astronautix.com/r/r-40b.html

A thruster itself (not an entire propulsion system) is a relatively simple component (nozzle with some valves) that isn't difficult to integrate. Thrusters are made by a host of different manufacturers and it's common to select different ones even in the same platform product line, as long as performance requirements are met.

It ain't rocket science. Oh wait, it is, lol.

[Dadhawk]

Originally Posted by shiumai

...I'd be more concerned if they ordered a brand new thruster costing us taxpayers more, when they had some that met the mission requirements in storage.

That's exactly what they are doing (see article above). They have 24 new multi-mission/one shot engines on order.

[shiumai]

Originally Posted by Dadhawk

That's exactly what they are doing (see article above). They have 24 new multi-mission/one shot engines on order.

If there are none in storage that meet existing requirements, then that's what they have to do. Sounds logical to me. Or, are you saying that they have existing thrusters in storage that would work, but they're not using?

[Spuds]

Originally Posted by shiumai

Understood and point taken. Here's some info on the particular thruster in the article:
http://www.astronautix.com/r/r-40b.html

A thruster itself (not an entire propulsion system) is a relatively simple component (nozzle with some valves) that isn't difficult to integrate. Thrusters are made by a host of different manufacturers and it's common to select different ones even in the same platform product line, as long as performance requirements are met.

It ain't rocket science. Oh wait, it is, lol.

I've heard that before lol.

[Dadhawk]

Originally Posted by shiumai

If there are none in storage that meet existing requirements, then that's what they have to do. Sounds logical to me. Or, are you saying that they have existing thrusters in storage that would work, but they're not using?

No, I'm saying they are spending money on overbuilt thrusters for a single use. Whether they have to be overhauled between launches they are still more expensive than they need to be for a "throw away"

[Ohio Enthusiast]

Originally Posted by Dadhawk

Whether they have to be overhauled between launches they are still more expensive than they need to be for a "throw away"

We don't know how (or if) NASA did the cost analysis, but it might be that the R&D needed for a new design or for reusing some other engine would have made a per-launch cost greater than reusing RS-25s (which hopefully required minimal investment to repurpose for SLS).

Also, according to Wikipedia the first 4 SLS flights use existing Shuttle engines, while the newly manufactured ones are "simplified RS-25E variant". Although this does fall into the typical government thinking of "lets use these spare parts now for cheap, even though they'll cost us a lot more in the long run - that's a problem for the next person to hold office".

[Ultramaroon]

Originally Posted by Dadhawk

That's exactly what they are doing (see article above). They have 24 new multi-mission/one shot engines on order.

Minimum order for price break on alibaba

[shiumai]

Originally Posted by Dadhawk

No, I'm saying they are spending money on overbuilt thrusters for a single use. Whether they have to be overhauled between launches they are still more expensive than they need to be for a "throw away"

I guess the point is they've already been built and (mostly) paid for, vs. designing and manufacturing brand new expendable rocket engines. 'Overbuilt' can also mean a greater factor of safety and reliability. Either way, it's over budget and late - I'm disappointed as well.