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Artemis I Launch Attempt Scrubbed

blogs.nasa.gov

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Re: Artemis I Launch Attempt Scrubbed

#21

Post by mabbo »

allenrb wrote: post #9

Consequences of choosing the wrong first stage fuel (hydrogen) are many. Those tiny molecules want nothing more from life than to sneak through the smallest of openings. Well, possibly second to mating violently with oxygen.

Like all engineering decisions, hydrogen is a choice with tradeoffs.

It's specific impulse ('fuel efficiency') is unbeatable. That buys you a lot more cargo capacity for the same sized rocket. And since this program is putting large items into lunar orbit, you need that badly.

But as you said, it's... complex to work with.

Hey it worked for the space shuttle.

Re: Artemis I Launch Attempt Scrubbed

#23

Post by tonetheman »

thetinguy wrote: post #17
JumpCrisscross wrote: post #16

We’ve been quoted $4bn per launch. If this pattern of delays turns out to be fundamental (a big, if plausible, if), what would the launch costs actually be?

Artemis is a federal jobs program.

Military budget for the year was 777B...

Give what you said all of the military is a jobs program also.

Re: Artemis I Launch Attempt Scrubbed

#24

Post by jmyeet »

allenrb wrote: post #9

Consequences of choosing the wrong first stage fuel (hydrogen) are many. Those tiny molecules want nothing more from life than to sneak through the smallest of openings. Well, possibly second to mating violently with oxygen.

“Wrong” by what standard? Hydrogen has the highest specific impulse but I’d much harder to work with. We have no better propellant.

A lot of other launch vehicles use RP-1, which is basically just kerosene. Lower specific impulse so lower payload capacity but it doesn’t need to be cryogenically stored and cooled with everything that entails.

That’s a fine choice for single use rockets but when you get into reusable rockets you now have a new problem: RP-1 burns and leaves a lot of carbon behind. This is costly and slow to clean.

For this reason SpaceX’s next rocket uses methane. Like hydrogen or must be cooled but not as much. Still it’s more complex engineering.

Artemis to me seems too expensive but it will be the most powerful launch vehicle ever created with the highest payload capacity.

So how is it wrong?

Re: Artemis I Launch Attempt Scrubbed

#25

Post by madaxe_again »

perihelions wrote: post #13

Likely no next attempt until October, per Eric Berger ( Ars Technica ): - "Hearing a rollback to the VAB of the SLS rocket is likely, but I don't have confirmation. If that happens, it is very likely that Artemis I does not launch before October 17, at the earliest." - "I'm told that Space Launch System program officials will recommend a rollback to the VAB to investigate the hydrogen leak. The Artemis I mission mana…

I have my doubts that it will ever launch - the way things are proceeding, they’ll miss October, push to ‘23, and will then end up with parts and systems ageing out due to wear and duty cycles - the rollback to the VAB alone incurs significant wear.

Meanwhile, starship will see its first orbital flight (likely not before a few RUDs) while SLS just grows mould.

That said, the whole purpose of SLS was to provide jobs and to retain technical expertise in the US, which it has achieved - actually launching the thing is almost besides the point.

Re: Artemis I Launch Attempt Scrubbed

#27

Post by somenameforme »

Robotbeat wrote: post #18
JumpCrisscross wrote: post #16

We’ve been quoted $4bn per launch. If this pattern of delays turns out to be fundamental (a big, if plausible, if), what would the launch costs actually be?

This is normal for any new launch vehicle. …which is why it’s often a good idea to not use a new launch vehicle on the critical path for your crewed spaceflight program. (Could have used LEO rendezvous of various types to go to the Moon.) https://spacecraft.ssl.umd.edu/akins_laws.html > 39. The three keys to keeping a new human space program affordable and on schedule: 1) No new launch vehicles. 2) No new launch vehi…

The initial SpaceX Falcon rocket was entirely privately funded, at a total cost of of ~$100 million. The first 3 launches were failures. The 4th launch was a success, and the rest is history. And that vessel would ultimately go on (through various again largely privately funded innovations) to revolutionize spaceflight.

The same is now true of the Starship, which is again being entirely privately funded. The cost is certainly going to be much more than $100 million, but also nowhere near the absurd extremes of cost that Boeing imposes on the taxpayer. At this point "we" have spent tens of billions of dollars on this catastrophe. And the icing on the cake is that if this monstrosity is ever deemed flight worthy, it will likely already be obsolete.

It's quite difficult to understand why giving a company billions of dollars a year, unless they succeed, does not seem to be leading to great outcomes. Maybe we should just give them more money. That'll fix everything.

Re: Artemis I Launch Attempt Scrubbed

#28

Post by xcskier56 »

mabbo wrote: post #21
allenrb wrote: post #9

Consequences of choosing the wrong first stage fuel (hydrogen) are many. Those tiny molecules want nothing more from life than to sneak through the smallest of openings. Well, possibly second to mating violently with oxygen.

Like all engineering decisions, hydrogen is a choice with tradeoffs. It's specific impulse ('fuel efficiency') is unbeatable. That buys you a lot more cargo capacity for the same sized rocket. And since this program is putting large items into lunar orbit, you need that badly. But as you said, it's... complex to work with. Hey it worked for the space shuttle.

Another trade off:

Liquid hydrogen is very low density, and requires extremely low temperatures.

This means that you need a much bigger tank for a given weight of fuel, and that tank needs to be insulated bc liquid hydrogen must be kept below 33 kelvin.

Both of these downsides can come close to negating the upside of increased ISP.

But the upside for SLS is that they already had engines that can run on hydrogen. Like you said, trade offs all around

Re: Artemis I Launch Attempt Scrubbed

#30

Post by numpad0 »

allenrb wrote: post #9

Consequences of choosing the wrong first stage fuel (hydrogen) are many. Those tiny molecules want nothing more from life than to sneak through the smallest of openings. Well, possibly second to mating violently with oxygen.

There are just as many hydrolox(hydrogen + liquid oxygen) as kerolox(RP-1 kerosene + LOX). Atlas, Delta, H-II, Ariane 5, Long March 5, to name a few, all use hydrolox.

I believe a part of reasons why launch attempts are called "attempts" is because of extreme scrub and failure rate of launch vehicle launches, and I think the fact that scrubs are now considered abnormal can be attributable to SpaceX and Elon Musk. I was old enough to remember watching last few of Space Shuttle launch attempts, and from my experience watching launch streams, scrubs and recycling due to hydrogen leaks, erratic sensor readings, upper atmosphere weather, and private boats and planes violating keepout areas were entirely normal events, with a global sole exception of the Soyuz launch vehicle flying from Baikonur Cosmodrome, which delayed or failed up to once in a decade or so.

Apparently it pisses off people in power, sometimes might have caused off-season human resource reallocations, but rocketeers basically never cared. That was until Falcon 9 started launching on first tries of each attempts.

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