NASA just weeks away from trying again with SLS Moon rocket launch NASA will attempt, for the third time now, to blast off its Space Launch System (SLS) rocket to the Moon in late September. Officials are targeting September 23 at the earliest, and September 27 as a potential backup should it have to scrub the launch yet again. Jim Free, NASA's associate administrator of Exploration Systems …
Hydrogen is used as propellant in other rockets (Ariane V comes to mind, or the "Long March" series) . It doesn't seem to be such a problem for other Nations. I'm not sure blaming the propellant is the good reason.
NASA should stop building its own rockets
I wasn't aware NASA has its own rocket factory.
== Bring us Dabbsy back! ==
There are permanent seals that are bolted tight. There are small filling connectors for when a tanker unloads into storage tank, operated by a skilled human. There is a great big connector on the quick disconnect arm. This connector has to handle a huge flow rate and disconnect quickly by remote operation just before launch. It may also have to reattach after a late scrub while it is dangerous for people to approach. It cannot be bolted as tight as the more permanent or less time critical connections.
This particular failure may be because the pressure was commanded way too high shortly before filling started. During the post scrub press briefing NASA avoided answering many related questions. The pressure was commanded too high. It was not certain that the high pressure caused the leak as at the time people could not safely inspect the quick disconnect. NASA did not say if the command came from software or a human. If it really was human error that caused the scrub then I would say that a human is still more reliable than Boeing software.
Hydrogen is tricky, but the biggest problem NASA is having is that they re-used the exact same tech they used for STS/Space Shuttle, which was known to be problematic but was somehow expecting it to work now? SLS is also a lot bigger and heavier, with a lot more propellant than rockets like Ariane V or Long March 5. Things get exponentially more difficult as you scale things up.
Take a look at last week's Rocket Report on Ars Technica.
That points out that the Shuttle averaged one scrubbed launch attempt for each successful one over its operational lifetime, with some launches having a many as 5 scrubs before a successful launch.
So, yes, hydrogen is difficult to handle anyway, and more difficult in bulk, but having Congress not only mandate that NASA build the SLS by reusing Shuttle technology, but prohibiting it from switching fuels or using more current technology certainly doesn't help the SLS to be more reliable than the Shuttle or to cost any less.
>SLS is also a lot bigger and heavier, with a lot more propellant than rockets like Ariane V or Long March 5
In addition these use Kerosene first stages and onyl uses H2 for in-space stages where you really care about performance/weight
SLS uses a H2 1st stage because of 50 years of expediency to get something working quickly and cheaply.
Hydrogen is a problem on other vehicles too. Hydrogen leaks became less of a problem for them as the operators gained experience and because their rockets are smaller. The problems come back when ground support equipment is left unused for months (last Delta IV Heavy had lots of scrubs). That is something SLS has to look forward to as Artemis 2 will be May 2024 (lies, damned lies and rocket launch schedules).
Hydrogen has other problems. The boiling point is far lower than other propellants and the low density requires enormous tanks and turbo-pumps. Try comparing to Raptor which uses methane:
Thrust: RS-25=2.279MN Raptor=2.3MN
Mass: RS-25=3177kg Raptor=1600kg
Diameter: RS-25=2.4m Raptor=1.3m
Cost: RS-25=$145M Raptor=$250K
After that, comparisons get more difficult as the use cases are so different.
Hydrogen engines (except on Delta IV Heavy) do not produce enough thrust for lift off and require solid rocket boosters (equivalent to about 8 raptors each for SLS). It takes ages for SLS to burn all its hydrogen so the main tank and engines are almost in orbit before separation. Hydrogen in a small second stage is an excellent propellant for high energy orbits or Earth departure.
The plan for Raptors is to light a large number of them so the much heavier rocket leaps off the pad really fast to reduce gravity losses. Raptors will burn through their fuel quickly and stage much lower. This makes reuse much simpler but requires a much more capable second stage. With a single launch, a fully loaded Starship can go to LEO but payload mass plummets for anything higher - even geosynchronous transfer. That massive stage two pays off with refuelling. From LEO, a refuelled Starship can take a full payload anywhere - even to the surface of the Moon and back to lunar orbit.
Yeah, words can be as slippery as H2 molecules in a sieve :-)
The plans was to launch. Something went wrong and the launch was scrubbed. They failed to reach the point of launch so could be a failed launch. Likewise, if a rocket ignites and starts going up and then explodes a mile or two up, arguably that was a successful launch but a fail in the flight, not actually a failed launch.
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Good news! NASA/Boeing have thought of this. Although Artemis 2 will carry crew on a rocket that has only flown once before the Artemis 3 crew will be on a vehicle with twice the flight heritage. For Artemis 4, the Interim Cryogenic Propulsion Stage (stage 2) will be replaced with the Exploration Upper Stage so the crew will boldly fly on a rocket that has never flown before. There is a bit of a reversion for Artemis 5 but the Booster Obsolescence and Life Extension program puts them back on track with a new booster design for Artemis 9.
>I'm not sure it was designed for any particular people;
It was totally designed around particular people
The whole point of going to the moon is to show off America Great
The original landings have faded a little, and the message of "during Vietnam and race riots at home we sent a bunch of white male fighter jocks to the moon" doesn't have quite the PR spin it had in the 60s
So NASA is going to put a women and person-of-color in the sequel. Although I suspect both will be ex-fighter jocks, unless they can find a way of not needing Navy cooperation in the recovery
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I don't understand the downvotes here. It seems pretty obvious that the only reason for Artemis is willy waving.
If you actually wanted to establish infrastructure or do science on the Moon, you'd use robots. The round-trip latency is only half a second and without the need to support life and bring it back, the deliverable payload is vastly greater and cheaper.
Actually, even if you want people on the Moon, you ought put some infrastructure there first. The current plan is just reckless.
SpaceX has been continuously denied the opportunity to test out their moon rocket Starship until SLS has a chance to go first. SLS is a 50 year old boring conventional design. Starship has the opportunity to fail in several new and amazing ways. Get the opening act over with and bring on the real entertainment!
Starship isn't ready to make its first orbital flight yet, but it's getting very close. Starship completed its first six engine static fire yesterday (which caused quite an impressive grass fire!), with the booster completing a spin prime of a load (maybe all) of its engines.
At a guess, it may be ready to try for a flight next month. It's going to be fun to watch when it does...
Where Lucy keeps pulling the ball away?
"Don't worry, we nearly got it launched last time. Just 3-4 more tries and we will definitely have it debugged.
(6 attempts later)
It seems it has been in storage for so long everything has gone a bit off, have to build another one. But don't worry! Sure she'll take right off on the first go!
(7 attempts later) SCRUB.
Bring them down? Not *take* them down?
So SpaceX is going to get Starship ready far enough ahead of the crewed Artemis to plop a lander onto the Moon and have it wait there until the crew arrive, at which point it'll go up to meet them, then bring them back as it goes down to the surface again?
Bring them down? Not *take* them down?
I love that idea. Pre-establish a surface to lunar orbit shuttle service before sending folk down. They could have a choice of flights back up depending on how long they wanted to stay. Sadly, I don't think even SpaceX are at the 'just refuel and carry on flying' level of re-use yet.
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