The chosen landing site for Artemis 4 takes it close to a monument to the first efforts to explore the Moon.
Finally, after a successful touchdown, all that remains is for Janus to unfurl its solar panels and wait patiently for the mission's crew to join it on the surface.
A bit of a technical appendix, following earlier discussions on the sizes of the Saturn Multibody fairings for Artemis, e of pi and I had a few discussions, and we can now present the following summary of just how all those components fit under the hood.
With regards to that last image.
At least it's real easy for the casual observer to tell which one's which.
So NASA is using a near (if not completely) identical method of carrying the Artemis Lander and Block V Apollo that they used for the old Apollo CSM/LEM? Well they already know it works, so I assume they're using "If it ain't broke..."
At least it's real easy for the casual observer to tell which one's which.
So NASA is using a near (if not completely) identical method of carrying the Artemis Lander and Block V Apollo that they used for the old Apollo CSM/LEM? Well they already know it works, so I assume they're using "If it ain't broke..."
Interesting to see NASA have teamed up one of their most experienced astronauts with one of their least experienced. Nathalie Duncan had her first flight with Freedom Expedition 32 in September 1996. I'm sure her experience with the Apollo Block V will be very useful, and it will be good to at last see a representative of the other 50% of humanity on the Moon, but I suspect there will be a fair bit of grumbling and accusations of tokenism amongst the astronaut corps and sections of the press.
Also, I wonder if Ed Keeler's grandmother (or maybe great aunt) was active in the pacifist movement in the '30s?
How big is Pegasus? It looks to me like it would have the same diameter as a Multibody stage--that is, 3 meters. And in the picture it might be twice as long as it is wide, if I sort of stretch it. That ought to give it a volume allowing about 18 tonnes of oxygen-hydrogen propellant, if the mass ratio is 6:1 as in STS, and the densities of liquid oxygen and hydrogen are such that there is 1.2 tonnes per cubic meter of the former and 1/12 a tonne for the latter-that is, the tank volume ratios would be 1:2.4 for a total of 1.4 tonnes per 3.4 cubic meters or average density of 412 kg/cubic meter.
18 tonnes seems far too low a reaction mass. Perhaps the advanced engines operate closer to stoichiometric ratio, at 8:1 oxygen to hydrogen, which I believe would also allow a higher ISP if the engines can take considerably more heat? Then the density would be 482 kg/cu m, and that kicks the mass up to 20--not a dramatic improvement but with higher ISP it might work?
I don't think so--I seem to recall Janus would mass at least 25 tonnes before starting the landing burn, and I'd guess Pegasus's empty mass to be at least 2 tonnes, so if TLi is 3100 meters/sec that seems to require an ISP of 570, which is 100 more than the ideal theoretically attainable from hydrogen-oxygen and better than any known chemical reaction can achieve.
So--is Pegasus bigger than it looks somehow, or Janus lighter than I thought, or what? TLi could be a bit lower but not a lot; the difference between a minimal energy Hohmann orbit and Earth escape velocity is pretty small! It's got to be in between these extremes somewhere.
The highest ISP I can figure they are using, 470, would give a burnout mass just under 21 tonnes after expending 20 to achieve 3100 m/sec delta-V. Is Janus under 20 tonnes then? But the full Artemis CSM/LM stack can hardly be that small, yet a full Pegasus can push the whole lot on to L2!
I think the Pegasus has to be somewhat larger in linear dimensions to do its job, especially since the unmanned lander mission has a manned-size Pegasus that is underfueled.
18 tonnes seems far too low a reaction mass. Perhaps the advanced engines operate closer to stoichiometric ratio, at 8:1 oxygen to hydrogen, which I believe would also allow a higher ISP if the engines can take considerably more heat? Then the density would be 482 kg/cu m, and that kicks the mass up to 20--not a dramatic improvement but with higher ISP it might work?
I don't think so--I seem to recall Janus would mass at least 25 tonnes before starting the landing burn, and I'd guess Pegasus's empty mass to be at least 2 tonnes, so if TLi is 3100 meters/sec that seems to require an ISP of 570, which is 100 more than the ideal theoretically attainable from hydrogen-oxygen and better than any known chemical reaction can achieve.
So--is Pegasus bigger than it looks somehow, or Janus lighter than I thought, or what? TLi could be a bit lower but not a lot; the difference between a minimal energy Hohmann orbit and Earth escape velocity is pretty small! It's got to be in between these extremes somewhere.
The highest ISP I can figure they are using, 470, would give a burnout mass just under 21 tonnes after expending 20 to achieve 3100 m/sec delta-V. Is Janus under 20 tonnes then? But the full Artemis CSM/LM stack can hardly be that small, yet a full Pegasus can push the whole lot on to L2!
I think the Pegasus has to be somewhat larger in linear dimensions to do its job, especially since the unmanned lander mission has a manned-size Pegasus that is underfueled.
The Saturn Multibody stages are based on the old S-IVB, so 6.6m diameter - that's what I meant with the caption, sorry it could have been clearer.
According to Part III post#7, the Pegasus diameter is 5.5m and it holds about 70tonnes of propellant. Pegasus got stretched a couple of metres shortly before I first posted an image of it, but the diameter stayed at 5.5m.
Is the lander-Apollo stack fairing load bearing for Artemis like the old LM fairing adapter was?
I'm no engineer but it seems like having the load forces of the Apollo V moving outwards to the main barrel of the fairing, then down, then having the load forces move back "inwards" to the S-IV during launch would result in a prohibitively heavy/complicated fairing.
I know that there was a long and interesting conversation about how load would be distributed through the Artemis stack during TLI, but what about during launch?
(related questions: what's the burnout G-forces experienced when using the "stretched" S-IV on Saturn multibody?)
I'm no engineer but it seems like having the load forces of the Apollo V moving outwards to the main barrel of the fairing, then down, then having the load forces move back "inwards" to the S-IV during launch would result in a prohibitively heavy/complicated fairing.
I know that there was a long and interesting conversation about how load would be distributed through the Artemis stack during TLI, but what about during launch?
(related questions: what's the burnout G-forces experienced when using the "stretched" S-IV on Saturn multibody?)
The Apollo is supported by the fairing. Saturn H03 (with IIP mods) can throw 84 tons to the Artemis parking orbit. Apollo plus the crew lander mass about 62 tons. The fairing being a little heavy is thus absolutely not a problem. (Also, some bracing off the lander support truss can pick up some of the load from the barrel of the fairing.)
As a side note, the right-hand fairing is the only new one. The 20m barrel widebody on the left is the same used to launch Freedom's Columbia Habitat and Service Module, and the two main units of the truss. The middle one is a standard DoD fairing used on Multibody M02 and M22 out of Vandenberg for launching...hmm, there's a smudge on my notes. Looks like somebody highlighted this with a Sharpie by mistake. Odd. Anyway, they use that one pretty often.
Nothing particularly arduous. Core+booster burn is the big one--it takes a bit of throttle work to stop it exceeding 4G before booster sep. With that done, it drops back, rising to a little under 3Gs just as the core burns out, then drops back and rises to 2.5 Gs as the S-IVC burns out.
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The middle one is a standard DoD fairing used on Multibody M02 and M22 out of Vandenberg for launching...hmm, there's a smudge on my notes. Looks like somebody highlighted this with a Sharpie by mistake. Odd. Anyway, they use that one pretty often.
So DoD and NRO satellites are much much bigger ITTL?
I can neither confirm nor deny, pursuant to national security. However, there have been known to be leaks around the edges of stuff like this, and perhaps if you re-read recent posts carefully, you'll find some of your answers.
let's look on Payload fairing used on rocket used by NRO
volume 10 by 3 meter ø for Titan IIID
see this PDF for more detail
Space Shuttle was change on demand of USAF for NRO payload
volume 18.2 by 4.6 meter ø
for Delta IV heavy Payload fairing used on rocket used by NRO
volume 13 by 5 meter ø
See this page for more Information
so having a Saturn 1 family rocket that launch more into space in this TL, NRO is very very happy
volume 19.8 by 6.6 meter ø
For the Japanese lunar astronauts, how about "Usagi" (rabbit) for the crew lander?
Turtledove Win!
My illustrations for Eyes has been announced as the PRELIMINARY WINNER - OTHER ARTWORK in this year's Turtledove Awards! I've posted a 'Thank-you' on that thread, but just wanted to say a special thanks to everyone who follows this thread and re-iterate my gratitude to e of pi and Workable Goblin for creating such a great timeline and letting me loose in it
My illustrations for Eyes has been announced as the PRELIMINARY WINNER - OTHER ARTWORK in this year's Turtledove Awards! I've posted a 'Thank-you' on that thread, but just wanted to say a special thanks to everyone who follows this thread and re-iterate my gratitude to e of pi and Workable Goblin for creating such a great timeline and letting me loose in it
My illustrations for Eyes has been announced as the PRELIMINARY WINNER - OTHER ARTWORK in this year's Turtledove Awards! I've posted a 'Thank-you' on that thread, but just wanted to say a special thanks to everyone who follows this thread and re-iterate my gratitude to e of pi and Workable Goblin for creating such a great timeline and letting me loose in it
No matter how critical or clueless I might seem, I take pride in being the first fan to comment on ETS, and the advent of your artwork here squared its appeal which was already in the top ranges of all threads here IMHO; you take into a visual dimension the seamless union of visionary excitement and rock-solid plausibility down to nuts and bolts of the text authors.
It is only just now that I see that the same day I last posted a query as to the Artemis designs, you posted yet more pictures I did not see until today, notably the one of the three Artemis payloads "under the hood." Which would have been helpful had I noticed them early, but I guess only the TLI launch picture was actually up before I headed off to work. Then I overlooked the later images.
My warmest congratulations to you, and to Eyes for your eminently well-deserved victory in this category! Having followed Eyes for some time (over two years now!) I can say with confidence that your contributions have elevated this already fine timeline into something truly superlative (see what I did there?My illustrations for Eyes has been announced as the PRELIMINARY WINNER - OTHER ARTWORK in this year's Turtledove Awards! I've posted a 'Thank-you' on that thread, but just wanted to say a special thanks to everyone who follows this thread and re-iterate my gratitude to e of pi and Workable Goblin for creating such a great timeline and letting me loose in it
)And in turn, I'd like to thank Nixonshead for being willing to put in all the time and effort he has over the past year in making this timeline so much more than it was or could have been without him. His art has really brought this timeline to life, and it's been a pleasure working with him. This award is richly deserved for that, and all the times he's put up with me changing images at the last minute or requesting honestly crazy ideas for images that he's pulled off so well. Congratulations!My illustrations for Eyes has been announced as the PRELIMINARY WINNER - OTHER ARTWORK in this year's Turtledove Awards! I've posted a 'Thank-you' on that thread, but just wanted to say a special thanks to everyone who follows this thread and re-iterate my gratitude to e of pi and Workable Goblin for creating such a great timeline and letting me loose in it
Archibald
Banned
My illustrations for Eyes has been announced as the PRELIMINARY WINNER - OTHER ARTWORK in this year's Turtledove Awards! I've posted a 'Thank-you' on that thread, but just wanted to say a special thanks to everyone who follows this thread and re-iterate my gratitude to e of pi and Workable Goblin for creating such a great timeline and letting me loose in it
Kudos. Well earned ! Your work is just, aaaaaaaaaaaaaaaaaaawww (per lack of superlative)