NASA flight controllers halted the first launch attempt after they were unable to verify that one of the SLS rocket’s four main engines—engine no. 3—had been properly cooled to a temperature of -420 degrees Fahrenheit prior to ignition…During a news conference on Tuesday evening, NASA’s program manager for the SLS rocket, John Honeycutt, said his engineering team believed the engine had actually cooled down from ambient temperature to near the required level but that it was not properly measured by a faulty temperature sensor…The problem for NASA is that the sensor cannot be easily replaced and very likely would necessitate a rollback to the Vehicle Assembly Building at Kennedy Space Center in Florida, a few kilometers from the launch pad. This would delay the launch of the rocket at least into October, and the space agency is starting to get concerned about wear and tear on a rocket that has now been stacked for nearly a full year.
Ifixit gives SLS a repairability score of 2.
not really
Hopefully this one will go better.
That would be generous. This isn’t the first time this has happened. Changing the batteries on the launch escape system is also super-involved, and the current launch dates are limited by them not expiring.
Also, the Orion capsule has a broken Power & Data Unit that they’re leaving in place because it would take a year to replace it.
But hey, if you got paid based on the number of billable hours, are you really going to make repairs easy?
“You don’t need that. Also, we don’t mind the weight and delta-v budget hit of carrying dead hardware into space; we’re just that cool.”
It’s really awesome that their decision involved weighing “increased chance of failure by loss of redundancy” vs. “increased chance of failure by having to take the whole thing apart and put it back together again”.
If they did pick the latter option, I’d suggest they not fly if there are any screws left over.
I think the constraint is with the batteries in the Range Safety (self-destruct) system. Closely related, but one should remember not to trigger them in the wrong order.
Ahh, you are correct. This is one for the extended xkcd maxim. If you do not perform these things in the right order, you will not go to space today, or maybe ever.
SLS was announced in 2010.
It is flying in 2022.
Apollo was announced in 1961. Its last flight, a number including 9 manned lunar flights, was in 1972.
SLS is just a slight reboot of the Constellation program, which dates to 2004. And the Orion capsule dates from about the same time without even the courtesy of a rename.
At least there’s no equivalent to the Ares I. Fun fact: the vehicle vibrated so badly from the solid rocket booster that the astronauts wouldn’t be able to read the displays. Their intended solution was to strobe the displays at the vibration frequency to freeze the motion.
That’s a helluva workaround.
It’s clever; I’ll give them that. Clever enough that they patented it:
But stupid that it was even necessary.
The vibration environment on SLS isn’t quite as bad as the Ares I, but it’s still bad. Bad enough that it was impossible to fly the Europa Clipper spacecraft on SLS:
But on the upside, they just decided to fly it on a Falcon Heavy instead, saving a bunch of money:
Didn’t the TLI on Saturn V also cause huge vibrations?
Only in a relative sense. Liquid fueled boosters are typically extremely smooth. As you go up the stack, you have fewer engines to average out the small thrust oscillations, and a lighter stage in general, so the amount of vibration goes up (the gee loads may also increase). Some comments from Apollo 10:
Where the S-IC stage and the S-11 stage were completely smooth, the S-IVB growled, rattled, and rolled during the whole burn. But you could actually feel little vibrations. It wasn’t a pogo - we never had a real pogo throughout any part of the flight.
Astronauts riding the Falcon 9 have described the same thing. First stage was very smooth; the second stage much less so. But I don’t think it comes anywhere close to the level of the Ares I, which shakes you to the point of blurring out the displays.
Wasn’t it Apollo 6 that had some bad pogo’ing?
ETA — I’ll answer my own question. Yes it was. I just looked it up. Per wiki:
For the first two minutes, the Saturn V launch vehicle behaved normally. Then, as the Saturn V’s S-IC first stage burned, pogo oscillations shook the vehicle. The thrust variations caused the Saturn V to experience a g-force of ±0.6 g (5.9 m/s2), though it had only been designed for a maximum of 0.25 g (2.5 m/s2). The vehicle suffered no damage, other than the loss of one of the panels of the Spacecraft-Lunar Module Adapter (SLA).
Pogoing is definitely within the realm of “vibration induced by combustion stability”, but not the origin of the solid rocket booster vibration of the Ares I, and I don’t think was the origin of the third-stage vibration of the Saturn V (which was probably just the low-level instability that all engines have). Pogo is a resonant effect involving propellant flow, which doesn’t apply to SRBs.
Cool.
Getting back to this question:
This little piece of information came out recently:
Here’s what is wild about the NASA purchase of commercial crew seats. For development and operations of crew, NASA is going to pay Boeing a total of approximately $5.1 billion for six crew flights; and it is going to pay SpaceX a total of $4.9 billion for 14 flights.
Now, Boeing is not NASA, but Boeing is the prime contractor for SLS.
Furthermore, the Commercial Crew contract is fixed-price, and it appears that Boeing is to lose money on it. That’s ok for everyone that’s not Boeing. But SLS is a cost-plus contract, so if Boeing does an equally poor job with managing SLS costs as they did with Starliner, NASA and therefore the taxpayer will foot the bill. We already know that SLS has been tremendously expensive, but so far that’s mostly just been development. The actual cost of the rocket(s) is still to come.
I hope I don’t sound too negative about Artemis. I really am excited about returning to the moon. Even with all the compromises and costs that SLS is imposing, it should still represent a much more sustainable program than Apollo. It’s just hard not to rail on Boeing and the other SLS contractors for the way everything has gone. Though if I really had to pin maximum blame on one person, it would be Orrin Hatch, for essentially forcing all of NASA’s rockets to use solid rocket boosters (because they are manufactured in Utah). That one single design decision has had so many negative knock-on effects that it’s hard to count.
IKEA. Swedish for spare parts.
back on the “to the moon” topic - with a rationale I haven’t read on this thread:
wasn’t it an important (more than?) suspicion that on the southern pole of the moon ice is expected?
Ice as in frozen H20?
which you can easily - through electrolysis - break up into H and O … being H a very reactive combustible and O a very good - ahem - oxidizer? - bang/wham instant fuel (ok, somewhat oversimplifying here - but you guys/gals get the drift)
So the way I see it, the moon is highly relevant as a potential “gas-station” for “next steps” and “things to come”.