I'm back from the Europa Focus Group meeting... Options

[edstrick]

And of course the real story only marginally matches the old story about one of the last 2 failures retrofiring early and the other late, due to timing errors relative to the range-radar's "mark" signal.

I've never seen (should go brousing Encyclopedia Astronautica etc) pics showing the airbags. They've been completely missing in every pic and model I ever saw, and I'm surprised there's no obvious trace of them in either the Luna 9 or 13 panoramas.

[JRehling]

The Kremlin, which wasn't used to having to publicly admit so many space failures in a row, was apoplectic at this point
[...]
At this point Korolev died due to his botched surgery

Things that make you go "Hmmmm."

[Bob Shaw]

And of course the real story only marginally matches the old story about one of the last 2 failures retrofiring early and the other late, due to timing errors relative to the range-radar's "mark" signal.

I've never seen (should go brousing Encyclopedia Astronautica etc) pics showing the airbags. They've been completely missing in every pic and model I ever saw, and I'm surprised there's no obvious trace of them in either the Luna 9 or 13 panoramas.

These comments about the airbags disturb me to some extent, as they simply *don't* appear in the historical record. What *do* appear are 'sleeves' around the lander ball itself, and yes, they do appear to split into two sections. Whether or not these are 'airbags' in the sense we now use them is, I think, open to dispute. The illustrations I've seen of the landing sequence didn't have a traditional Pathfinder airbag deployment, but did go into such details as the radar, the rod which struck the ground first, and so on, so I wonder if the airbag story is a little bit of modern gloss!

Have a look at the image!

Bob Shaw

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[JRehling]

The trouble with Rehling's idea is that all the instruments on the Bowling Ball (or, to give it its correct name, the Jovian Moon Impactor) -- except for the seismometer -- are supposed to peer through ports in the outer hull. There's no way to do that if the outer layer is crushable

Something crushable could provide ports as well -- you would just have to have the inner sphere end up using whichever ports happen to end up on top, and either have big ports (like the face mask of a football helmet, but in multiple locations) and some tolerance for the orientation not being guaranteed to match precisely when everything comes to a halt. How this might play out in terms of affordable mass, I don't know.

[Guest_BruceMoomaw_*]

The Europa Ball has little teeny camera ports -- of the sort that could easily be concealed by a crushed outer layer -- and it carries 16 of them to maximize the chances that some will be pointed in the right direction for both close-up and longer range Post-landing photos. (It seems to have no provision for descent photos -- something else, I think, that needs to be changed and easily could be, even given its lack of attitude stabilization.) One could, I suppose, put the camera lenses outside the crushable layer and run optical-fiber lines to them (which do, in fact, run from the camera ports on the current version to a single CCD, with other optical-fiber lines running from the 12 sample cups to a single Raman spectrometer) -- but I'd assume that such O.F. lines would be extremely vulnerable to damage when the layer is crushed.

So the plan, to repeat, is to make the whole thing so rigid and solid-state that it can survive up to 10,000 G -- as with the most sophisticated penetrator designs. (NASA's tests in the late 1970s included repeatedly crashing penetrators even into solid boulders, with a whole variety of scientific instruments onboard, including seismometers 100 times more sensitive than Apollo's -- and the only one that suffered any problems was a CCD camera on the afterbody.)

As for the history of Luna, the JBIS article (Sept. 2000, by Asif Siddiqi et al) is extremely thorough in its sources, and cites both the most recent and detailed Russian accounts and recently declassified US tracking of the Luna probes to confirm that Lunas 5 and 7 didn't brake at all, while Luna 8, during its tumbling final descent, fired its braking engine for only 9 seconds and then in the wrong direction. There's also a lot of detail on the airbags (including Soviet documents grousing about their design problems) -- the Soviets may have kept silent about them at the time to try to make the landings look more like the more sophisticated full-fledged Surveyor soft landings. The article is co-authored by Timothy Varfolomeyev, who's done somc excellent earlier stuff for JBIS in digging up, archaeologist-style, the true space past of his own nation's former secretive tyranny -- including an earlier JBIS article on the first block of Luna missions (1958-60), which I may report on later over in our "Moon" section.

[Phil Stooke]

Here's a diagram of the Luna 9-style landers' landing sequence, showing the discarded padded shell... I'd prefer to call it that. The expression 'airbags' was never used by the Soviets until Pathfinder, when Russian sources started referring to the Luna 9 padding in the same way. I don't want to say it's intentionally misleading, it is probably a translation issue. But there was no sudden inflation as we would think of in airbags.

We have no idea how far the landed capsule rolled after being ejected from the carrier stage. The padded shell and the carrier rocket may be close by but hiddem by the tilt of the camera, or just too far away to be sen clearly. I have suggested that a big 'rock' (mapped as such by the Soviets) near Luna 13 might be its shattered carrier rocket stage.

Phil

[Guest_BruceMoomaw_*]

The article is extremely explicit that there WERE inflatable airbags, and that they were the cause of the Luna 8 failure. (The craft began tumbling at 2 rpm 13 seconds after the inflation began.) The precise cause of the leak was discovered 5 days later. One letter from a co-worker describes Korolev -- who valued this program very highly -- as seemingly teetering on the verge of slitting his own throat after the failure.

Quoting the description: "During flight to the Moon, the Automatic Landing Station [aka the lander capsule] was covered in a thermal blanket. Within the blanket, there was a second covering, this one comprising an expandable rubber chamber with a a protective Kapton shell. Compressed gas from a spherical bottle mounted on the separable Compartment #1 [one of the two side equipment pods jettisoned from the main craft during retrofire] would inflate this second covering into two independent cushioning airbags which would protect the actual lander cocoon moments before impact....

"After the Luna 8 accident... Babakin's engineers introduced changes primarily related to the sequence of operations before landing. In the Ye-6 [previous design], inflation of the shock absorbers was carried out before main engine ignition. But as two senior engineers from the Lavochkin Design Bureau later noted, the sequence was changed for the 'Babakin variant': 'It was established that it was essential to carry out the inflation of the shock absorbers after ignition of the braking engine, to prevent harmful rotating moments that arose when the shock absorbers were inflated before braking engine ignition.' This reasoning seems to be supported by at least two contemporary accounts of the Luna 9 mission from 1966 in which the authors note that the airbags 'were prepared for landing while the engine was working.' Because the compressed-gas bottle for the shock absorbers was in a container attached to Compartment #1 which separated before engine ignition, Babakin's engineers moved this bottle to the side of the I-100 control system compartment on the main bus. One source notes that another difference on Luna 9 was that the attitude control thrusters were used in a continuous mode rather than intermittently to stabilize the spacecraft after airbag inflation."

There is an accompanying diagram of the Luna 9 design from a Soviet technical magazine showing Luna 9, complete with the new position for the airbag gas bottle, and there are very extensive bibliographic notes for all of this -- including the 1966 articles that mention the airbags. The thermal cover over the entire capsule-airbag assembly was jettisoned at the very start of the landing sequence. (The I-100, by the way, was also the spacecraft control system that was the bane of the whole program from Jan. 1963 through May 1965.)

[Bob Shaw]

Here's a diagram of the Luna 9-style landers' landing sequence, showing the discarded padded shell... I'd prefer to call it that. The expression 'airbags' was never used by the Soviets until Pathfinder, when Russian sources started referring to the Luna 9 padding in the same way. I don't want to say it's intentionally misleading, it is probably a translation issue. But there was no sudden inflation as we would think of in airbags.

Phil

Phil:

Yes, that's the illustration I'd seen somewhere before, I think in one of the old Novosti Press propaganda booklets from the late 60s - with all the photos ludicrously airbrushed to death for no real reason, even the ones of cosmonauts looking really pleased at having been given lots of, er, flowers.

It's a bit like the Prop-M Mars 3 rover-on-a-string being 'remembered' once Sojourner came along. All very interesting, but indicative of a certain degree of spin...

Bob Shaw

[Guest_BruceMoomaw_*]

Additional notes:

(1) The braking engine was shut off at 250 meters altitude (actually not very much lower than the optimal but very flexible planned burnout altitude of the 1962 Ranger retromotor), and "seconds later" the lander capsule was ejected. In the case of Luna 9, it landed "halfway up the inner slope of a 25-meter crater." Luna 13, by contrast, touched down on a plain, so I suppose it's conceivable that it did see its braking stage at a distance. (One of Alexei Leonov's space paintings shows the Luna 9 braking stage lying on its side just a short distance from the capsule, but of course this is poetic license.)

(2) Luna 8's "airbags had been pierced by a plastic mounting bracket of the stabilization petals that were supposed to be opened after landing. The bracket had broken off and the sharp edges had punctured one of the rubber airbags. The entire sequence of events could be perfectly reproduced in the laboratory. In the end, the problem was traced back to one single worker who had made a mistake during the manufacturing part of the process." Lucky for him that Stalin wasn't still around.

(3) There's also a photo of a model of the Luna 9 braking stage in the Tsiolkovskiy Museum that clearly shows the inflation bottle for the airbags in its new position.

(4) The 10-cm shift in Luna 9's post-landing position occurred "possibly because the diminishing water supply in its thermal control system had changed its weight distribution."

Any further notes I have on the Luna program will be moved over to the Moon section where they properly belong.

[Guest_BruceMoomaw_*]

Getting back to Europa: the most interesting purely scientific news to come out of the Focus Group meeting was three separate reports that converge pretty well on a likely surface composition.

John Spencer reported on several years' worth of near-IR spectra taken through Keck adaptive optics which have a spatial resolution of only 200 km, but a spectral resolution fully 66 times better than Galileo's -- and which, to the researchers' shock, nevertheless showed NO new spectral features beyond those seen by Galileo. The very smoothness of the Keck spectra indicates that the salts in the ice are in flash-frozen brine (e.g., amorphous) form rather than crystalline; I wonder whether the same Jovian radiation that breaks up Europa's ice into amorphous form may have randomly redistributed the dissolved salt ions through the same process.

All three reports (including two other studies by John Dalton and T.M. Orlando) indicate a good spectral match to ice mixed with large amounts of sulfuric acid, Mg sulfate and Na sulfate. Remove any of those three substances and the spectrum doesn't match nearly as well.

[Phil Stooke]

Bruce, I hadn't known about the inflatable bladder. That's good to know. Thanks.

Phil

[Bob Shaw]

Bruce:

If you get the chance to point us at some pictures it'd be rather good; is there any hint of the volume of this bladder? I think that's a far better word than air-bag, which conjures up the wrong associations these days...

Bob Shaw

[Guest_AlexBlackwell_*]

John Spencer reported on several years' worth of near-IR spectra taken through Keck adaptive optics which have a spatial resolution of only 200 km, but a spectral resolution fully 66 times better than Galileo's -- and which, to the researchers' shock, nevertheless showed NO new spectral features beyond those seen by Galileo. The very smoothness of the Keck spectra indicates that the salts in the ice are in flash-frozen brine (e.g., amorphous) form rather than crystalline...

I'll just note the Spencer et al. paper is currently in press with Icarus.

[Guest_BruceMoomaw_*]

Correction: the spectral resolution of the Keck spectra was only 18 times better than Galileo's -- not 66 times better. That's still a lot better, and Spencer said he's abandoned his hopes that New Horizons' long-distance spectra of Europa might tell us anything new about its composition.

Nope, I have nothing on the volume of the Luna airbags.

While, we're on the subject of salt, one EGU abstract ( http://www.cosis.net/abstracts/EGU06/04537/EGU06-J-04537.pdf ) says that Cassini's dust analyzer has pegged the composition of the dust particle streams being spewed out by Io -- while they contain some sulfur and potassium compounds, they're mostly just plain old NaCl. Io is sprinkling table salt all over the Solar System.

[Guest_AlexBlackwell_*]

Correction: the spectral resolution of the Keck spectra was only 18 times better than Galileo's -- not 66 times better. That's still a lot better, and Spencer said he's abandoned his hopes that New Horizons' long-distance spectra of Europa might tell us anything new about its composition.

Since this had been one of your favorite hobby-horses, hammered into our brains with your now-familiar as-I-have-saids and I-repeats, I guess the more interesting question is have you abandoned it?