NASA signs deals to put a rocket under Artemis flights until 2029 NASA has picked an engine supplier for its controversial Space Launch System (SLS) program weeks after an audit chastised the space agency for blowing its budget. The space agency said on Saturday it will plunge $1.79bn into a new order of 18 RS-25 engines from Aerojet Rocketdyne. The engine, which was originally developed for …
"The same reliable engines that launched more than 100 space shuttle missions have been modified to be even more powerful to launch the next astronauts who will set foot on the lunar surface during the Artemis missions."
I hope this is simply an oversimplification. Surely we all know that if you take a reliable engine and modify it to create more power, the reliability of said engine take a natural hit?
But then I'm not a rocket scientist.
Yes - a modified design is, by definition, not the same design.
Hence the requirement to freeze the F9 Block 5 design for human flight.
But it does inherit a significant amount of the testing of previous versions, and remember that the engines went through several iterations during the shuttle programme.
To be fair, the RS25 engine was originally designed to be re-used, albeit with refurbishment between flights, and so would have had a conservative maximum power rating. Use the engine too hard and it'll require too much refurbishment and/or may have to be retired early.
If you're only going to use the same engine once then you're already in a position to eke a bit more power out of it. According to NASA: "Engines on the shuttle ran at 491,000 pounds of thrust (104.5-percent of rated power level). After analyzing temperature and other factors on the engine, the power level was increased for SLS to 512,000 pounds of thrust (109 percent of rated power level)."
This suggests that there have been no modifications, simply a re-assessment of what is a safe maximum power level now that the engine is strictly single use (although a number of the engines being used for early launches are ex-shuttle).
But as Steve Todd says above - it's not cheap. SLS was being developed before Elon Musk even got started. I don't expect that it will last long once there's been a few flights of a re-usable super-heavy lift rocket.
it's typical for military equipment to have a design rating that is based on the thing NOT being replaced very often. In the case of a nuclear reactor, let's say, the metals will become damaged by radiation over time. But the limits are set so that you can use the thing for 30 years and not have to replace it completely during the life of the ship. Similarly, a rocket engine is probably running at certain limits according to design margins and maximum stresses based on expected material failure modes, yotta yotta yotta. Additionally, CYCLIC stress is a major factor. Think "cracks that grow". At higher power levels you're more likely to have a crack that grows to an "unrepairable" size, but without catastrohic failure, at the higher power level. Lower power levels would let you "thermal cycle" it a lot more without getting a catastrophic failure (i.e. re-use the thing).
Even though that's just a projection of what I've seen before in military equipment, it's probably close to reality. Material strength and failure modes and how to prevent catastrophic failure, and operating limits based on minimum detectable design flaws and design margins, along with periodic X ray of materials and various other kinds of maintenance. It's how you do it, yeah. But for ONE-TIME use... if you stress it up to the breaking point, you're getting the most possible use out of it!
(but for warships, you also have WAR TIME limits, which are a *bit* different)
I used to look after ratings of certain industrial gas turbines. Regular operation at 13MW could be anything up to 8000 hours a year, with refurbishment roughly at similar intervals.
The same units could be cranked up to 20MW for very brief periods in an emergency - for literally 10 to 20 hours, and require a comparable refurb to the 8000 we'd see in routine op.
In practise you'd never use the unit on that basis, unless a national emergency dictated need and the appropriate cashflow were present.
... seem to be obeying the law.
The law requires NASA to 'pick' Space Shuttle contractors where practicable. That is the exact word of the law. Being impractical is not an excuse to use another contractor. If it is possible to work with AJR engines then NASA has to make that happen - no matter what the consequences. The consequences are ARJ picking the biggest number they can get congress to pay. Congress really wants to pay so each critter can crow about how much federal expenditure he got for his state.
Bridenstein has actually squeezed a hint of sanity into NASA's plans. The Orion capsule is approximately ready but the only thing that can lift it is SLS (by design and by law). SLS+Orion cannot get to low lunar orbit so there is a threat of LOP-G orbiting a point between the Earth and the Moon (Near rectilinear HALO orbit). NASA needs a ride from NRHO to the moon and back, which is precisely what they have asked for (not from LOP-G to the Moon and back). This means Artemis can continue even if when LOP-G gets delayed.
LOP-G components can launch on commercial rockets. The transfer module, decent vehicle and ascent vehicle can all launch on commercial rockets. Because of the schedule and the limited supply of SLS launches (one per year) these things have to fly on commercial rockets because SLS will be busy launching Orions. Bridenstein has effectively limited SLS to launching only the missions that congress has required by law to launch on SLS. (Europa Clipper is supposed to go by SLS too, but it has to launch soon and Artemis has eaten all the available SLS's before the deadline.)
Perhaps AJR's enormous bill will be big enough to satisfy congress to they won't tie NASA hands even more tightly.
"What are they hunting for?"
Hopefully a place to put a MOON HOTEL, or at least a few mining camps for rare earths and things with high value, high enough to justify going to the MOON to get them.
And of course, an "interplanetary space port" hub. "Moon" becomes the new LAX [let's say].
It's my understanding that there's a LOT of Titanium on the moon. You could build long distance space ships with this. And structures. And if it's Titanium OXIDE, processing it would release OXYGEN.
But as for using 'Artemis' in the name, I think the answer is very simple: Artemis is kinda like Rosie the Riveter for Ancient Greece. And so it's (probably) just a symbol of putting the first WOMAN on the moon. Or it could mean more, maybe 'bold exploration' or similar.
[on a side note, according to Wikipedia, the Temple of Artemis at Ephesus was one of the 7 wonders of the ancient world]
We all know the SLS is just the Yanks keeping people employed - single use rockets in this day and age - really?
I expect to see more delays etc until NASA head off as supernumary on a Bezos or Musk flight to the moon.
Given Space-X impressive record they would be the front runners
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