UKC

Artemis 1 (https://www.nasa.gov/artemis-1) is scheduled for launch on Monday 29th August. Exciting to watch.

A manned moon landing is currently planned for Artemis 3, in 2025.

In reply to Rob Parsons:

Not sure about 'back to....'

In reply to bouldery bits:

Better not to feed the idiots with oxygen.

In reply to john arran:

Not enough space to send them to the moon... Yet

In reply to Rob Parsons:

Atremis is the sister of Apollo apparently. Neat name. 

In reply to broken spectre:

Bloody clever those NASA bods!

She's also goddess of the Moon.

In reply to Rob Parsons:

Forget “SPAM in a can”, it’s “Pork in a Barrel”.

In reply to bouldery bits:

youtube.com/watch?v=YSZoqYElqVE&

In reply to morpcat:

Where's the B ship when you need one 😂

In reply to Michael Hood:

was it B Ark?

In reply to Rob Parsons:

Including some women, I gather.

In reply to Rampart:

Yes.

Better in my OP would have been to write 'A crewed moon landing is currently planned for Artemis 3, in 2025.'

No specific implications intended.

In reply to wercat:

I think you're correct - the books are on my bookshelf but they've not been opened for several years - I can't even remember which of the five books it's in although no doubt someone on UKC will just know - is that someone you?

In reply to wercat:

Both.  It was ship B of the Golgafrinchan Ark Fleet, or B Ark for short.

https://hitchhikers.fandom.com/wiki/Golgafrinchan_Ark_Fleet_Ship_B

In reply to john arran:

Currently there are five rovers supposedly on Mars, but really they're in monument valley Utah. I spotted the goose

In reply to Michael Hood:

Oh I think it's a great many of us!

In reply to Michael Hood:

Last episode of the first radio series, so presumably the first or second book?

In reply to Rob Parsons:

When is it being launched, UK time? And where can I watch it, preferably on TV?

In reply to aln:

It is scheduled to launch at 1.33, subject to weather and fuelling conditions. I don't know if there is live terrestrial TV coverage, but the NASA website is streaming the launch:

https://www.nasa.gov/content/live-coverage-of-nasas-artemis-i-mission-to-th...

In reply to aln:

1.33pm. Live coverage on BBC News channel.

In reply to nufkin:

Back half of the second book, Restaurant 

In reply to Rob Parsons:

Just got both kids down for a nap with 15 to minutes spare. Tuning in for the countdown!

In reply to morpcat:

Oh well

In reply to Rob Parsons:

Tune in again Friday, fingers crossed for then

In reply to Rob Parsons:

Thanks everyone. Unfortunately I have an appointment and I'm going out now 😟

In reply to CantClimbTom:

an engine bleed required? i wonder how many of their countless simulations involves this?

In reply to Rob Parsons:

Oh well, in the meantime let's watch this piece of ancient machinery for the umpteenth time

youtube.com/watch?v=ViNcBQ8cDA0&

In reply to mbh:

He is the very model of a modern Spectre operative

In reply to Rob Parsons:

In reply to wercat:

Yes, yes, yes, of course he is, but the best bit is after that. What an astonishing piece of machinery, especially those engines.

In reply to mbh:

That they were.  Then abandoned in favour of the space shuttle.

Moving on to the new, Artemis and SLS using refurbished Space Shuttle Main Engines (SSMEs) in expendable mode is one of the most ridiculous things about the SLS program.  One of the most amazing rocket engines to date, phenomenally expensive to the point it only made any sense with reusability, and they’re disposing then with every launch.

Speaking of insane, launching the humans with segmented, solid rocket boosters attached in the 2020s.  Wow.  How did it come to this?  Oink oink.

In reply to wintertree:

If that's an allusion to your previous 'pork-barrelling' comment, what's the background story?

In reply to Rob Parsons:

Eric Berger - who I think is one of the best space journalists out there - has a go at a balanced piece on it.

https://arstechnica.com/science/2022/08/the-sls-rocket-is-the-worst-thing-t...

NASA's SLS rocket program has been a hot mess almost from the beginning. It has been efficient at precisely one thing, spreading jobs around to large aerospace contractors in the states of key congressional committee leaders

Compare the costs to the in development SpaceX Starship program, which looks to be coming up 100x cheaper per kg to any orbit and 20x cheaper by developed costs.  Neither SLS nor Starship have orbited yet, but Starship has had a much more flight and hardware intensive test program.  

Payload to moon:

• SLS - 27 tons 
• Starship - payload to moon - 100 tons

Per launch cost

• SLS - $4.1 Bn (expendable)
• Starship - < $ 0.1 Bn (reusable)

Development and program cost:

• SLS - $41 Bn
• Starship - $ 2 Bn?

Just imagine what NASA could have done without congressmen forcing them to execute the SLS program.  

Edit: as Berger says, the worse problem is perhaps not the financial cost but the missed opportunity cost.  Just imagine what 10 years and $40 Bn could have done for reusable space flight vs expendable rockets.  Nothing new; it’s 30 years since the USAF built a prototype vertical take off and landing, reusable space rocket - https://en.wikipedia.org/wiki/McDonnell_Douglas_DC-X - NASA took that program over, crashed the flight article and shut it down…. SpaceX have now been able to achieve it for far less money in large part given the advances in commercial compute power, sensors and manufacturing technology.  

In reply to wintertree:

Thanks - that's a useful article.

In reply to mbh:

Those launches were so exciting to watch live - I remember rushing home from junior school to watch some of them (Apollos 7, first manned Apollo, 8 loop round the moon, 9 test the lunar lander docking etc in earth orbit, 10 take the lunar lander close into the moon's surface, 11 land on the moon, 12 ditto, 13 how exciting does it get when things go wrong)

In reply to wintertree:

Considering how inspired I was by Apollo, I can't quite believe how underwhelmed I am by this cobbled together amalgam of old engineering. 

In reply to wintertree:

Presumably they're approaching the end of their practical service life anyway as they run out of hours (minutes!), NOS parts and retired engines to cannibalize. IIRC at least one of the shuttle missions already came very close to disaster when accumulated engine repairs (plugged, damaged injectors) began to fail ejecting those repairs, creating hotspots and mechanically damaging the nozzle's cooling system. I'm struggling to google the story, could be misremembered but might jog someone's memory.

jk

In reply to jkarran:

Yes, they’re refurbishing the shuttle engines for the next few flights at around $50 Mn per engine.

After that, they’re building new copies of the most expensive rocket engine of all time - intended for reuse - and dumping them after one flight.  At around $ 150 Mn per engine - https://arstechnica.com/science/2020/05/nasa-will-pay-a-staggering-146-mill...

Starship’s engine is comparable power, will be reused and costs around $ 1 Mn/engine.  So we could be taking about 1500x higher costs per engine per flight for SLS.

In reply to wintertree:

Yeah, that's pretty daft. I can see the sense in burning up tired engines from a defunct program but new reproductions, not so much! I presume the reason they're not flying with Starship's Raptor engines is politics and the inertia of a huge institution?

jk

In reply to jkarran:

It’s a very different engine that needs a very different sort of rocket so the engines could never be swapped, but the development program for a raptor based rocket is looking 20x cheaper than SLS’ program with perhaps a 100x lower launch cost.  The overarching reason NASA are doing it the way they are is because a group of congressmen have pushed through legislation requiring them to do so, largely it seems because of the sheer quantity of federal money that then goes to jobs in their state.  Which is the same reason why the SRBs are segmented - because they require overland transport from their factory to the east coast shuttle launch site so have to be in parts. Which is why they have inter-part seals.  See: loss of Challenger. People pretty high up in NASA have tried and failed to have SLS cancelled.  It’s important to recognise none of this farcical waste is NASA’s fault.

Should have left it to Gromit.  But only Shaun The Sheep was onboard.

In reply to Rob Parsons:

Another launch attempt today, Saturday 3rd September.

In reply to Rob Parsons:

Scrubbed again. Leak in the fuel tank.

In reply to wintertree:

This would be funny if it wasn't so expensively wasteful.

https://www.theguardian.com/science/2022/sep/03/nasa-artemis-1-launch-calle...

In reply to Offwidth: This bodes well for hydrogen fuelled cars?

In reply to kevin stephens:

Not sure of the link there.  Rocket use/pump liquid hydrogen in massive quantities. If it's at atmospheric pressure it needs to be down to about 20Kelvin to be liquid, although rockets are under pressure but you get the idea... it is very cold! Also H2 is a really small and sneaky molecule and is unbelievably good at leaking past seals and through bearings etc.

A lot of the research for hydrogen vehicles has been on how to store hydrogen without  these kind of difficult, cold fun and games. Either people have been using tanks very much like diving cylinders (simple proven technology) and also in how some unfortunately expensive and exotic materials can store hydrogen on their surface. Don't think the rockets are super relevant  to cars?

In reply to CantClimbTom: Nasa’s problem is a leaking seal on a connection. As you say H2 is a very small molecule and much more leaky than say LPG. This leakyness is potentially a major limitation on operation and maintenance of hydrogen fuelled cars

In reply to kevin stephens:

H2 was used as a fuel in these same rocket engines for all of the Space Shuttle flights. The basic engineering must have been sorted out long ago.

In reply to Rob Parsons:

Stages 2 & 3 of Saturn V's as well so 1968 (manned launch Apollo 8) if not earlier (design/testing).

Edit: seems like the Saturn 1 launches had 2nd/3rd stages using H2 back in 1964.

In reply to Rob Parsons:

There's nothing basic about containing liquid hydrogen.  

See the wiki page on Hydrogen embrittlement [1].  It flows through solid metal, emerging as gas in the tiniest voids far, cracking them wider until the metal part fails.

I think there's an awful lot yet to be learnt about working with cryogenic liquids, and it's only learnt experimentally.  Any rocket design that strays from exact configurations that have been tested before faces unknown.  SpaceX found this with their COPVs in the liquid oxygen tank with AMOS-6.  There's a lot of materials physics still to be learnt... The difference is SpaceX (and Rocket Lab) have been rapidly iterating hardware to learn, NASA have been mandated by congress to spend 100x as much building a new rocket before flight testing.  Hardware and flight rich testing finds problems that lie beyond the bounds of our understanding.  It's the way to go...

[1] - https://en.wikipedia.org/wiki/Hydrogen_embrittlement

In reply to wintertree:

It's really unfortunate isn't it, the kinds of metals (or rather FCC/BCC structure if you're going full-bore nerd) that is good for mitigating high cycle fatigue are exactly the ones most prone to hydrogen embrittlement

To digress again back to vehicles (sorry!) there is a definite parallel with diving cylinders and vehicle hydrogen tanks. Both get routinely pressurised to the 200bar kind of pressures, and store non liquified gas (unlike say propane bottle on a forklift). With diving cylinders the service life of aluminium ones are generally capped at 4 years due to use/refill stress cycles and fatigue concerns, whereas steel ones last a long long time. But with hydrogen storage people may require aluminium due to hydrogen embrittlement stress cracking.

Imagine having to replace your car's fuel tank every 4 years regardless of mileage

In reply to CantClimbTom:

Only reason I’ve not bought my dream car - the XJ220…

In reply to wintertree:

I think this is probably a considerable example of rocket engineering being far harder than "the science".  There must be conflicting considerations here, making a good seal in a situation where you also need a wholly reliable near instant disconnection complicated by very low temperatures where structures and materials behave unexpectedly in situations hard to test in the lab

In reply to CantClimbTom:

It's really easy; just stick it to carbon. There. Fixed it for you. You're welcome

In reply to Longsufferingropeholder:

John Carmack and his outfit, Armadillo Aerospace, don’t come up on here much.  A lot of their content went offline a while ago but IMO they were the trailblazers in terms of both

• VTVL rocketry using consumer grade sensor units and consumer grade compute hardware (following on from the USAF Delta Clipper which validated VTVL rocketry 20 years before internet idiots started saying it was impossible to land rockets vertically…)
• Methalox engines

Armadillo was massively underfunded (multi millionaire’s hobby project, basically) but they were the trailblazer for what SpaceX has achieved.  Musk offered Carmack a job but he went to work for Oculus.  I was surprised at Carmack’s choice.

With reference to wercat’s post; indeed rocket science is really quite simple but rocket engineering - including materials physics - is up there with the hardest engineering problems.  Hydrogen rockets look good from a noddy rocket science perspective, move on to the engineering and it’s been clear for quite a while that methane is the future, assuming we don’t want to get in to nuclear thermal for launch…

In reply to wintertree:

Just a small point of order, anyone who's interested enough to read this far down this thread but hasn't yet read Ignition by John D Clark, read it. 

Edit: turns out you don't even have to acquire it https://library.sciencemadness.org/library/books/ignition.pdf

In reply to Longsufferingropeholder:

Thank You!

Downloaded and taken a quick look, immediately clear that I'm going to enjoy reading it!

In reply to CantClimbTom:

Same here!

In reply to Longsufferingropeholder:

Thanks for this! I started reading it immediately. For a technical book, it is very readable!

In reply to John Stainforth:

It’s amazing he lived to write it. 

Not unrelated is one of my all time favourite blog posts - https://www.science.org/content/blog-post/things-i-won-t-work-dioxygen-difl...

In reply to wintertree:

easy for space cadets who think they can set up a base on moon/mars...

In reply to CantClimbTom:

Just imagine, industry has been storing hydrogen for centuries!

200bar cylinders like the ones available at any gas supplier are spun steel and have normal cylinder life (Type 1).

Type 2 are aluminium and wrapped to increase the storage pressure.

Type 3 have a thinner aluminium liner and more wrapping and are used in trucks, buses, trains etc at 350 or 700bar.

Type 4 are plastic/composite liner and composite wrapped, that's what the cars use at 700bar as they are lighter. Expected life 20 years or vehicle life.