Using Ed's excellent video as my reference, it looks to me like the nucleus -- the actual cometary body -- is located significantly to the upper left of the center of the apparently spherical coma around the comet.

In addition, although my eyes may be playing tricks on me, I can convince myself that I see the faintest of traces of linear features within the coma emanating from the nucleus "in" to the somewhat denser center of the coma.

I ask myself about the dynamics of such a violent eruption. I'd have to guess that such a cloud of gas and dust, which has expanded to be larger than Jupiter in physical size, would have to have quite a bit of mass entrained within it. In other words, it seems like an *awful* lot of mass shot off that comet all at once. And if the faint linear features I think I can see are really there, then the mass shot out in a pretty straight linear column, forming a center of an expanding cloud at the place where the comet *was* when the explosion occurred, not anywhere near where the comet is *now*... the energy of the release being sufficient to separate the comet from the center of the expanding cloud.

Are there models out there that allow for such an energetic release of material from a comet? Could you actually get the pressures and temperatures in the ices and dust and rocks that make up the comet for an explosion of this magnitude?

Or do we need to be thinking about impact processes, here?

Obviously, you can postulate an impactor within the Solar System both big enough and with a large enough relative speed in re the comet to have done this. Can you also postulate an endogenous process that would account for it as easily?

-the other Doug

I'm betting the ultimate response is going to be to find a compromise position in which the SARJ will be parked and from which it will never thenceforth be moved. Yeah, it'll impact power budgets a little -- but the solar cells were always designed to give good margins for running more equipment than is now being planned. I don't think ISS will have rolling brownouts.

-the other Doug

See, I've been saying that the features along the boundaries of HP looked to me like the fine laminations you get at the edges of hydrothermal vents since last Martian fall. It's be really nice to find some mineralogical support for it!

BTW, last I heard (again a while back), there was still a pretty committed contingent on the MER science teams who favored a hydrothermal vent theory. I know we have a few people from those teams who post here on occasion -- can any of you comment on the thinking of the science teams as of late?

-the other Doug

Unfortunately, no. The HTC was just a little legged device that you could pick up and haul around with you, in which you could hang a big bag to put smaller sample bags in and on which you could hang collection tools, like core tubes, a hammer, a scoop and a set of tongs.

The wheeled cart, the MET (Modularized Equipment Transporter) was only flown on Apollo 14. It would have been flown on Apollo 15, had that mission been an H mission (45 hours on the surface, two 5-hour EVAs) as originally planned. But it wasn't ready yet for even Apollo 13.

The interesting thing is that the MET seems to have slowed down the crew more than it helped. Hauling it along took more effort than just hanging all the same tools off of clips on the backpacks would have...

-the other Doug

Just a couple of quick points:

- The photo is indeed from Apollo 12. The hardware on the ground is the Apollo Hand Tool Carrier (HTC). This equipment was not carried on Apollo 11, since on the first landing, the crew was not expected to wander more than a few tens of meters from the LM.

- The positive pressure from within the suit would indeed have blown the helmet out of one's hands as soon as the neck ring was disengaged.

- The visor assembly (called the LEVVA) fitted over the actual pressure helmet. You couldn't get to the neckring to unlock it while the LEVVA was on top of the helmet. Therefore, you couldn't even take the helmet off in the configuration shown.

- A human being can retain consciousness for about 30 seconds in the absence of oxygen. After that, he/she falls unconscious, and within another 30 seconds, brain damage has begun. A couple of minutes go by like that, and you're just plain dead.

-the other Doug

In my humble opinion, the phyllosilicates are a number one priority. These clays seem to be the only things that preserve traces of a Mars which differs significantly from the current planet.

They may have been formed as early as at the very end of the LHB, but these clays were formed before sulphuric acids began pouring out of the interior and the entire outer surface of the planet was coated with sulphates. This is likely the only period in the history of Mars when conditions were truly favorable for life to develop, and as such are most interesting to me. (It has always seemed to me that we need to study extraterrestrial life before we can truly understand how life actually works. Until then, we're stuck behind assumptions that we can't see beyond.)

There seems to be precious little of this phyllosilicate material exposed on the surface. The question is, was there not much to begin with? Or was it more ubiquitous but now has been covered with lavas and/or coated with basaltic dust cemented together by sulphate salts? Investigations of the clays, and of the contact between them and the surrounding terrains, will go a long way towards painting a picture of very early conditions on Mars.

Now, if Meridiani shows significant clay exposures, I'd be all for landing there. We already know how benign the surface conditions are, and how likely it'll be that we can land MSL there safely. But the more we can place clay exposures into a geologically significant context, the more we learn. I'm not positive how much context we'll be able to derive in such a flat location -- you'd be almost totally dependent on entering medium- to large-sized craters to get your drill holes into the stratigraphy.

I'd rather find places we can land safely and then approach outcrops on cliff faces and hillsides. Seems a little more likely to show us context. Of course, I could be wrong...

-the other Doug

And my guess here is that it won't be visible to observers in the Western Hemisphere... *sigh*...

-the other Doug

Could be lighting -- there was good sunlight along the belly of the orbiter as it separated from the ET, perhaps the sun angle simply was advantageous in highlighting sparklies that are always there.

Interestingly, I thought they weren't supposed to launch into cloud decks as low as the one they launched into...? Maybe the post-Columbia launch restrictions are being eased a bit?

-the other Doug

That was a little odd, though -- at ET sep, saw a huge number of little sparklies, more than normal, and there was a continuing flow of high-velocity particles which seemed to come from the direction of flight (behind the camera). More than I can recall on prior missions, anyway.

I'd think that by the time the orbiter had backed off a ways, its RCS wouldn't be impinging on the ET. I wonder what was blowing off the nose of the tank and being propelled back along the flight vector so fast?

-the other Doug

Yep, saw that -- sort of a corner of my eye kind of thing. Looked like a small piece of something, and as you say, way too late in the profile to be of concern.

-the other Doug

Smooth launch thus far, no sign of major foam loss or anything like that... looking good!

-the other Doug

I don't know that we got any real explanation for the ball... but at least we could see that you had your live audience absolutely spellbound!

Good work! I'm looking forward to seeing this concept mature and develop.

-the other Doug

It doesn't matter, up to a certain point, how much mass you can loft. Jupiter will *always* be harder than Mars (for a lot of reasons, including its distance from the Sun and the radiation environment). Neptune will *always* take a lot longer to get to than Jupiter.

We won't see any major opening-up of outer planet options until and unless there are some revolutionary new propulsion technologies developed, I'm afraid...

-the other Doug

In addition to Jim's excellent answer, there is one major item that the Shuttle designers made manually controlled, for *very* good reason. The landing gear.

You see, when the gear are deployed, they cannot be retracted without external help. Since landing at 300+kph without one or more of the gear down would destroy the vehicle, the gear are designed with a lot of "positive deployment" features. The short version is, once they are down, they are staying down until external hydraulics are attached to retract them.

So, if the gear were ever to deploy in orbit, you would never get that orbiter back. You can't make a successful entry with the gear doors open. That's why the gear are protected with a separate arming switch and a manual circuit breaker. If the gear were capable of being automatically deployed, that would open up te potential for a short circuit or a bad line of code (or just an electrical surge) to cause the destruction of a multi-billion-dollar vehicle.

Yeah, you could always automate the landing gear for unmanned flight. But you'd degrade its capability for re-flight by a small but significant fraction -- and by NASA's rules, you'd not again be able to man the spacecraft in that configuration, since it opens up a few single-point failure modes that would result in loss of crew.

-the other Doug

There were a variety of discussions beginning in 1961 (when the Saturn family began to be designed) through 1969-70, when the Saturn assembly lines were shut down. And while many types of payloads for the Saturn series were identified, when it came down to funding programs, cheaper (though less capable) alternatives such as the Titan III family of launchers won the day.

Remember, in the 1960s, the Atlas-Agena was the Delta II of the day -- the cheapest thing available that would get a few hundred kg out of LEO. If you needed to boost more, you had the Atlas-Centaur, which was more expensive but required for larger probes. (Sort of like the basic Delta IV or Atlas V -- and about the same degree more expensive). By the late 60s, you had the Titan III family, including the Titan-Centaur, which was just about the same in lifting power as a Saturn IB. The Titan III family were even more expensive than the Atlas family, and so only very large flagship missions (with accordingly large budgets) could afford to use them.

Now, as we've gone up through the Atlas to the Titan III families, costs have ranged to be comparable (in values corrected for inflation) on the low end to what a Delta II used to cost, and on the high end what a Delta IV Medium or an Atlas V Medium would cost today.

Then came the Saturns. A Saturn IB cost more than a hundred million dollars, in 1966 dollars. A Saturn V cost a third of a billion. (I'm quoting numbers by memory, but I think I'm in the right ballpark.)

Even with economies of scale, we're talking about, in 2007 dollars, spending three to five billion dollars for your launcher alone.

Any wonder no one ever decided to spring for a Saturn for their Mars or Jupiter mission?

However, there is nothing wrong with making the most of the designs and experience that came out of the Saturns. Heck, the tools and dies for the S-IC were kept warehoused for a number of years, IIRC. Some Saturn processes could probably be improved on, of course -- the manufacture of the S-II's forward bulkhead, for example, involved detonating small bombs behind a sheet of aluminum to press it into a rigid form on the other side. (I kind you not -- and it was hailed as a brilliant solution to a tough problem in its day.)

It would seem that detailed plans and some tools and dies were also saved for the J-2 and F-1 engines, as well. The J-2X is supposed to be an upgraded J-2, based in large part on the older engine, and I know I have seen early proposals for the Ares V which involved actually building von Braun's already-designed, uprated F-1A engines (1.8 to 2 million pounds of thrust, as opposed to the 1.5 to 1.55 million-lb-thrust F-1). (Yeah, I know, it ain't Newtons. So sue me... ) So, some legacy Saturn hardware/designs could ease the development path for Ares.

I must say, though, that I'm happy with the decision against using SSME's in the Ares V. A big part of the SSME design is its throttleability, which is only required on Shuttle because of the need to manage aerodynamic stresses on the stack during ascent. The Ares V has absolutely no need for throttleable main engines -- to use them would only increase expense. And to remove the throttleability, you'd need to redesign the things so much that you're in essence creating a brand new engine.

-the other Doug

Having parts of the spacecraft framing these vistas provide us psychological referents. It vastly increases the ability to imagine yourself actually *in* the place you're looking at.

I think it says something about the human desire/need to explore that these images, which include spacecraft "framing" views, are somehow more satisfying than any others.

-the other Doug

Since there were no other reports around the world of unusual meteor activity during this period, it seems there are only a few possible explanations for this quite interesting report:

1) These meteors were a portion of a coherent body which broke up very late in its approach to Earth, such that the footprint of the activity was very limited. This would mean that the entire event would have taken place over the course of minutes and not hours -- but in this kind of circumstance, I can imagine that five minutes would seem like an hour to people in the path of the meteors.

2) The event was some kind of freak weather event. However, as much as the discussion of this possibility has been lively, I can't imagine that one could collect samples of hailstones that would last for very long in the summer -- even in the cool air that would follow such a severe storm front. And hailstones are so identifiable as ice, I can't imagine the account not making reference to this obvious compositional data. And finally, I can't imagine anyone mistaking lightning in a thunderstorm for meteors in a clear sky. Too many factors argue against this option, I'm afraid it doesn't hold up.

3) The inhabitants of this district had their summer crops decimated by drought, but knew that the Ottomon Emperor would be demanding his tribute (likely in foodstuffs) in a month or two. They looked at the food they would have to survive the winter and decided that, if they paid their taxes, they'd most all starve to death. So they pled for mercy by telling the story of a killing heat wave, and embroidered it with a mystical fall of stars from the very sky. If I had to bet, I would lay odds that this is the most correct answer.



-the other Doug

True. The problem is that there was literally no market for Saturn Vs, aside from Apollo and Skylab. I seem to recall that NASA floated the prospect around to every potential market, including planetary probe developers and commercial interests (comsats, powersats, etc.) and got no takers. Even after estimating the economies of scale that you mention.

There was, and is, simply not a paying market for huge launchers. The only reason the Ares V is being developed is to support Constellation/Orion -- heck, there have still been no buyers for the Atlas V Heavy or the Delta IV Heavy. If no one is willing to pay the costs for those vehicles, I doubt the Ares V is going to be used for much of anything beyond Orion.

-the other Doug

Actually, the Shuttle is a beast unto itself when it comes to man-rating a launch vehicle. As designed, it cannot be flown unmanned -- you would need to make several major modifications to it if you wanted to fly it unmanned, which were considered to be too expensive (and, in some cases, dangerous) to build in.

But the Shuttle is its own launch vehicle in some ways -- the main engines are integral to the manned vehicle. So you cannot actually fly any portion of a Shuttle stack unless the orbiter is manned.

So, the Shuttle flew for the first time (and has always flown) with "exception waiver" documents. The basic approach is that there are some issues, inherent in the design of the vehicle, which render it potentially unsafe -- the location of the orbiter in the stack and the inability to shut down the solid rocket boosters once ignited, among other things -- which make the vehicle impossible to man-rate. So the Shuttle flies, every single time, with signed waivers which state that the program managers and crew are willing to undertake the risks associated with the items that cannot be man-rated.

In that way, the Shuttle has never actually been man-rated.

The Ares I approach will also require a Level One waiver for the use of a solid rocket booster as its first stage, for the same reason the Shuttle requires the same waiver -- the motor, once ignited, cannot be shut down. And, in at least that one aspect, it, too, will never actually achieve the status of man-rated.

-the other Doug

99.99 percent of dust movement on the Martian surface is due to straight-line winds, not dust devils. I wish we could lose this obsession a lot of people have with "dust devils" being responsible for every cleaning event of every surface on Mars... *sigh*...

-the other Doug

Yep -- but I believe that color version is from Surveyor III. It's from one of the missions that carried the robotic scoop. You can tell because the scoop was used to dump some soil onto the footpad so the camera could study its cohesiveness, grain size/distribution, etc.

-the other Doug

There were several different missions proposed to make use of the amazing capability provided by the Saturn V -- Mars landers, outer planet flybys and orbiters, Venus orbiters... a plethora of missions that could all benefit from the incredible lifting capability of the massive Saturn.

They all ended up shelved. Mostly because a Saturn V was immense in every respect, including its cost. It became glaringly obvious that no one was willing to spend the kind of money it would cost to buy a Saturn V to launch their unmanned probe.

They became incredibly reliable vehicles, but they were never cheap.



In some ways, we need to figure out how not to *ever* have to do things like that again. But first, let me say a couple of things:

The guys at Marshall, German and not, overdesigned the vehicle such that there was enough margin to absorb potentially fatal events and keep going. Not just keep the crew alive, but keep going.

Apollo 6 seemed to have a lot of unrelated problems when it flew, that's true. But they actually boiled down to only two basic problems with the first two stages of the rocket (with one simple wiring error compounding the problem), an easily-solved problem with the in-flight ignitor system for the S-IVB, and an easily identified and fixed problem with the materials used in the SLA adapter between the S-IVB and the CSM.

The Germans built those vehicles (especially the early ones) to telemeter so much information about themselves that the problems were rather easily diagnosed and fixes readily identified. So, while the problems seemed to be nearly insurmountable, the direct way in which the problems could be diagnosed led to a lot of confidence in the performance of the next rocket.

But...

The Apollo-Saturn development philosophy of "All-Up" testing was an *extremely* risky approach. It relied on the design and, moreso, the engineering philosophy upon which the Saturn was based being *so* well done that you just had to have confidence based on the engineering. Period. It's true that independent testing of the stages incrementally would have taken too much time (and incidentally cost more money) -- but in Mueller's original concept, he was willing to man a Saturn V after only a single successful test flight.

Saturn V had a magnificent flight record, mostly due to the margin built into all of its systems by those methodical Germans. But even after the deadline had been met and the time pressure was off, we nearly lost a crew when a malfunctioning engine came within about one second of vibrating itself out of the thrust assembly and tearing into the tankage above.

The problem with a huge and expensive launcher like a Saturn V or an Ares V is that they will always be too expensive to test a little bit at a time, and so will have to be over-engineered. Problem is, aerospace engineering these days seems to be all about doing as much as you can within your power/mass envelope, to cut your margins as slim as you possibly can and still get away with it. So I have doubts that the Ares V will be as immensely successful as its predecessor.

But I have no doubts that the all-up concept, carried over from Apollo to the Shuttle, will continue to prevail and that NASA, in its arrogance, will likely plan to man the Ares I and place Orion equipment for actual manned flights on the Ares V -- both after one successful test flight.

-the other Doug

That was basically referencing the Apollo 13 discussion. The "peril" was in fact more than mild, but it's difficult to present it as such via documentary footage.

-the other Doug

This is still representative of the first and most fascinating (to me) self-portrait image I ever remember seeing -- even though it is only a very small portion of the spacecraft in the portaiture:



This is actually not the image I truly recall -- that one was taken in low-res 200-line mode, while this one here was taken in 600-line high-res mode.

-the other Doug

Well, John -- I certainly can't speak for the uninformed populace of the 21st century. But back in the early 1960s, one of the points that Kennedy hammered over and over again was that he had made *this* committment precisely because it required us to expand the envelope in engineering and materials sciences. He didn't think that anyone, much less the engineers and scientists, were going to be able to pull new technologies out of the hat simply because their President said it was possible.

One of the main reasons for going to the Moon was to develop technologies, and moreso, to develop the technologists required to do the developing. Kennedy thought (and rightly so, IMHO) that America needed the new engineers and scientists that a Moon program would create more than it needed a political victory or a few hundred kg of Moon rocks.

-the other Doug