The T+4 event was the paper covers on the RCS thrusters blowing off of the vehicle. These covers were changed in the RTF process, from simple butcher paper covers attached with rubber cement to an origami-like design that opened a pocket of folded paper into the oncoming airflow as the stack picked up speed.

The new covers were expected to pull off at much slower speeds than the old covers, and did in fact pull off just as the stack was clearing the tower. I believe the vehicle was going something like 60 miles per hour (or roughly 100 kph for our European friends) as it cleared the tower, and the covers were supposed to come off at between 50 and 80 mph.

The old covers didn't come off until the vehicle was going *much* faster, several hundred miles per hour, and a few of them had flown back and bounced off the forward windows and their windowframes, causing some minor damage. This fix was intended to put an end to that.

-the other Doug

Today, July 26, is the 34th anniversary of the launch of Apollo 15.

-the other Doug

Reply to Bruce:

The technologies required for the types of life-support systems you'll need for deep space exploration is *already* being developed on Earth, at far less expense than testing it out on an orbital space station. It doesn't make sense to start flying such systems in space until you've developed one that works well in simulations on the ground. And the tests have been underway for years, now.

As for ISS being so unlike a deep space mission technologically (i.e., it needs resupply, it has no closed-loop life support system, etc.), that's not the point. Consider Gemini -- it contributed almost *nothing* to Apollo in terms of technology. Apollo was designed before Gemini -- and if you think NASA has a bad NIH problem in regards the Russians, you should have seen NAA in regards to McDonnell-Douglas when it came to taking advice from Gemini experience.

Gemini was absolutely essential to the success of Apollo because it taught NASA how to fly the missions. It taught NASA how to train the crews, how to train the misson controllers, and how to manage a real-time mission that lasted up to two weeks.

There was *absolutely* no other reason to fly Gemini than to provide the kind of real-world experience to the appropriate NASA centers and agencies that was required before they could even *think* about attempting the Apollo flight profiles.

I think that NASA could not have effectively *flown* a long-duration mission (of 6 months or longer) to deep space without having done it in LEO several times. Many, many times -- enough times to have encountered all of the various problems that can possibly come up due to the length of flight and the inevitable breakdown and servicing of the equipment.

The details of the equipment do not matter as much as the processes you develop, both in the crews and on the ground, to manage all of the contingencies. I simply do not believe that NASA could have transitioned straight from two-week shuttle missions into 9-month to 3-year deep space missions without flying some intermediate step, like a LEO station.

And face it, international or not, you have the same problems justifying *any* LEO station from a scientific standpoint. LEO stations are just not really justifiable from a scientific standpoint -- almost everything you can do on a manned LEO station can be done far more cheaply (and usually just as well) on an unmanned platform.

In my opinion, ISS is justified by providing the operational experience you need to consider mounting long-duration deep space missions. That is its only justification, just as operational preparation for Apollo was the only justification for the Gemini program.

And I do understand that long-duration mission management experience *did* exist, it was just all Russian. But I still insist that it is unreasonable to expect NASA to be able to learn the real operational lessons they needed to learn from Russia's operational experiences. When it comes to operational experience, it is almost impossible to learn from other programs, and especially from other cultures. You can codify that experience, turn it into management theory, create process specifications from it, and then teach it -- but even then, you don't really learn it unless you *do* it.

-the other Doug

I'm in complete agreement with the IAA. I think that manned expeditions to near-Earth asteroids are the logical next step in manned solar system exploration, and that Mars is better left to robots for the next 20 to 30 years.

But I'd like to see manned exploration and engineering evaluation of near-Earth asteroids starting in about 10 years. (At that rate, I may yet see another human being "set foot" on another world before I die...)

As for lunar exploration -- there is only one good reason for it, and that's because exploring new vistas is good for the soul. But I don't expect that argument to carry any weight on Capitol Hill, much less with the scientific rationalists that tend to populate this board...

-the other Doug

It *may* be karstic -- but I think the simpler answer is that the jumbled bedrock under this sand is the ejecta from Erebus and Terra Nova. They are craters, so they had to have emplaced ejecta blankets when they formed. And we're approaching their rims.

Why posit karsts to account for the uneven base of bedrock when we *know* the terrain must have been jumbled by the impacts?

-the other Doug

Oh, and for mini-TES' question -- Bruce was referring to a comment made by President Dwight Eisenhower late in his term. He gave a speech in which he sounded a warning against simply giving what he called the "military-industrial complex" everything it wanted simply because it wanted it. He pointed out that the large aerospace companies (they were mostly just airplane manufacturers back then), and all the companies that built tanks and guns and ships, had a very narrow world-view that *required* you to believe you were going to fight one major war and several smaller skirmishes every generation. That belief was their reason for existence, so they believed it very strongly.

They still do.

-the other Doug

I disagree with the postulate that the ISS is entirely useless.

ISS is not all that useful (especially in its present configuration) for scientific research. Most of the research that can be done on the ISS can be done better and more cheaply on science STS flights such as Columbia's last flight. Or on unmanned satellites.

But, in my humble opinion, the ISS is absolutely required *experience* for anyone who wants to travel beyond the Earth/Moon system and out into the greater solar system.

ISS is a learning laboratory on how to mount multi-year missions. Once you have figured out how to keep a crew alive and well on the ISS for a good fraction of a year, you've figured out how to send people to other planets on trips that will last from months to years.

NASA engineers had a belief about the Russian space station program -- that the Russians used crude and unreliable technology that constantly exposed their crews to needless danger. That the Russian stations broke down because Russian engineering was inherently inferior to American engineering.

ISS is proving the NASA engineers wrong -- equipment breaks down, be it in space or on the ground. Even bulkheads and other structural elements that are given a full reliability factor of 1.0 (never, ever expected to fail) can indeed fail given extraordinary circumstances.

The Russians found this out early on, and developed systems that can be serviced on-orbit. They even came up with techniques for servicing equipment that was never meant to be serviced. But us Americans, we wouldn't allow ourselves to learn those lessons, because it was *easier* to believe that the Russians were simply semi-competent entrants into the space game.

It is my belief that if the U.S. had decided to mount a manned Mars expedition without going through the learning curve of operating an ISS-style station for several years, the expedition would end in abort at best, and loss of vehicle and crew at worst. That this would have been inherent in the engineering mindset that believed you can design and build each and every system on such a complex spacecraft with *no* potential for disastrous failure.

Granted, such a station doesn't serve many other purposes beyond teaching us how to keep people alive and well, and keeping their spacecraft working properly, over months and years of flight time. Which is why the ISS *seems* to be such a waste. But unless we want to give up on the idea of manned solar system exploration, we *have* to gain this kind of experience before we can move on.

So, give the ISS a break. Everyone needs to spend some time in grade school before we can think about graduating into high school, much less attending university...

-the other Doug

Back in April of 1997, I flew from Chicago to London overnight. This was back when comet Hale-Bopp was reaching its brightest, with its most extensive tail.

I happened to be on the left side of the cabin, looking to the north as we traveled east towards Europe. The cabin lights were down low (it being the middle of the night), and my eyes became dark-adapted.

A glowing display of northern lights, green at the base with red and gold streamers, carpeted the planet, and Hale-Bopp hung near the top of the streamers, its tail beaconing upwards like a ghostly watchtower's lonely beam, guiding lost ships to safe harbor.

I don't think I'll ever, ever forget that view.

Oh, yes -- I love to fly. Especially with a window seat.

-the other Doug

The way you phrased that is interesting, since my argument is about heat.

If life exists on Titan, it would have to be adapted to very, very low temperatures. To the extent that any probe or rover we send to the surface of Titan would be considered "superheated" and would pump a not-insignificant amount of heat into the local area around the probe.

Thus, I think you could expect any terrestrial probe searching for Titanian life would kill any such life before it could get close enough to even look at it. Not only kill it, but possibly force it into such rapid decay that nothing recognizable as ever having been alive would ever be observable.

So -- for the sake of this thread, I offer the hypothesis that we cannot settle the question of Titanian life, because looking for it will destroy it utterly -- and that this raises serious ethical concerns over any such attempt.

-the other Doug

That was my first theory -- that the Hills were the original brecciated floor of Gusev, uplifted (either tectonically or by impact) over the water level from the time when Gusev held a lake and uplifted (obviously) over the embayment of basaltic lava flows that later occupied the crater.

But it's the MER science team itself that refutes this conclusion, and states categorically that the rocks in the Hills are in fact pyroclastic and volcanoclastic in origin -- i.e., emplaced by both ashfall and pyroclastic flow. The rocks were later altered by water, to greater or lesser degrees, most of them to a degree consistent with the upward migration of groundwater.

So, we're left with a sequence that covers the floor of Gusev with pyroclastic and volcanoclastic material prior to the uplift of the Hills, prior to major water alteration and prior to the most recent basalt fill. A really deep core of the floor of Gusev ought to yield, from the bottom up, the shocked, breccia-and-impact-melt original crater floor, volcanoclastic and pyroclastic layering, lacustrine materials (these last two perhaps interleaved in cyclic sequences), and finally a basaltic cap emplaced during the building of the adjacent Tharsis Dome.

-the other Doug

Here is an image returned by Opportunity on July 20:

Navcam image

That *has* to be an impact crater in the center of the image. It even has ejecta aligned circumferentially in the crater walls.

I'm no expert as to the focal length of the navcams, but this thing looks like it might be three or four feet across -- while not "tiny," it's also a rather inconvenient size for a primary impact crater on Mars

Even disregarding size, this thing looks very, very much like a secondary crater to me -- the impact wasn't energetic enough to push the largest pieces of ejecta out of the crater. Although I admit that the rest of the ejecta may be covered up by the drifting.

Isn't it interesting, too, that the ejecta arranged circumferentially around the inside of the crater looks a lot like the small, dark rocks we see littering the ground in between drifts?

I'm starting to think that this whole area has been showered with relatively low-velocity debris. A number of times. And if the freshness of some of the smaller craters is any clue, it seems to happen regularly, the latest perhaps quite recently.

So, the next question is: Where is this debris coming from? Impact? Volcanic expulsion? Other? And how can *any* of these processes account for the relatively large number of small craters seen, in varying stages of degradation (and, therefore, of varying ages)?

-the other Doug

I know that the MER science team (in various interviews) has characterized much of the "poorly sorted clastic rock" they have found in Husband Hill as either volcanoclastic or pyroclastic, preferring those models over impactoclastic (i.e., brecciated) mult-clastic rock. I'm assuming they've decided upon this interpretation based on both the appearance of the rocks and the elemental analyses performed by the APXS, Mossbauer and mini-TES instruments.

-the other Doug

Jibsheet looked like a conglomerate, too, but of rounded pebbles. Though either could be brecciated rocks -- but they look more like terrestrial congolmerates.

-the other Doug

The lunar regolith compacts very, very quickly into a material with some cohesiveness and pretty good bearing strength. The surface is only "soft" for the first inch or two (a little more on crater rims).

Yes, that first inch or so gives you a tiny advantage -- but not that much.

-the other Doug

I have the (in)famous Ranger issue of National Geographic, but it's somewhere in storage right now and I don't have it at hand.

What I don't recall is how the hard-lander "ball" was to be controlled in attitude during the retro-rocket firing. Was it spin stabilized? I sure don't remember it having anything like a sophisticated RCS. Perhaps a control-moment gyro system? A CMG wouldn't have to be all that heavy, since the ball was fairly light.

But I do recall that the lander only really had the one-axis seismometer, a transmitter and a battery. No camera, no other particles and fields sensors that I recall off the top of my head.

-the other Doug

It's not necessarily linear -- the easiest way to increase payload is to use a bigger booster. The MERs pretty well maxed out the capabilities of the Delta IIs used to launch them, and as of 2003, there really were no larger boosters available.

Delta IIs are proven technology, relatively inexpensive (compared to most of the rest of the options), and let you send something about the size of the MERs to the Martian surface.

Heavier-lift booster configurations (like some variations of the Delta IV and the Atlas V) are just starting to come on line, and will probably be used to launch MSL. But they're new, the companies that produced them spent a *lot* of money to develop them, and they're going to be quite a bit more expensive than the Delta IIs, especially at first. Whether that's $100 million or less, it's still significant.

Also, increasing the size of your lander package by a few kg isn't just a matter of adding a little more fuel to your rocket. Every pound you land on Mars costs in increased mass of *all* of the previous stages -- in MSL's case, the Skycrane would have to carry a little more fuel, the wheel suspension will have to be rated to survive touchdown with 5 kg of increased mass, the TMI stage will have to be a little more powerful, and since it will have to carry more fuel, the stage(s) of the booster will have to be more powerful and therefore heavier -- as you backtrack to the rocket sitting on the pad, every pound of extra payload you want to land on Mars can add hundreds and even thousands of pounds of additional fuel required to get it there. (To land less than 20,000 pounds on the Moon, Apollo had to launch a rocket that weighed nearly seven *million* pounds at lift-off. And it takes less overall energy to get a pound of mass to the lunar surface than it does to get it to the Martian surface.)

And on top of all of that, when you increase your lander mass and move to a new, bigger booster, you have to design all of the interfaces from scratch, you have to redesign your cruise stage, you have to validate and possibly redesign your parachute, you have to validate your heat shield configuration -- all of those things can make moving from a Delta II up to a Delta IV or an Atlas V more expensive than the simple increased cost of the booster.

So, maybe an extra $100 million would cover it. Maybe it wouldn't. We'll eventually transition to heavier-lift boosters, but y'all have to understand that this will inevitably lead to increased development and mission costs.

-the other Doug

Besides, while each of these classic ring segments share some gross characteristics, they all show a certain amount of differentiation within the ring (especially in the large rings) and are made up of thousands of "ringlets." After having seen how many thousands of ringlets exist, it seems rather silly to speak of Saturn having "seven rings" (A through G). Maybe we should come up with another nomenclature -- something like "ring domains."

After all, there is precedent for changing nomenclature when we get higher resolution images of planets. Just look at Mars -- while some of the current naming conventions pay homage to the old names based on telescopic observations of the albedo patterns, the modern names are all rather different and now refer to the landforms we've only discovered in the last 30 or so years. If Sinus Meridiani can be transformed into two regions, Meridiani Terra and Meridiani Planum, then why can't Saturn's A ring be redesignated "Ring Domain A" with sub-domains reflecting variations in structure and composition?

And, just remember, for those who wax lovingly over the "olden days," we'll always have the Encke and Cassini Gaps...

-the other Doug

OK -- just so long as they're not circling Uranus...



-the other Doug

A "windscreen wiper" (or "windshield wiper," as we Americans call it) woud end up, over time, scratching the coatings of the solar cells so badly that they would lose effectiveness. (Try tossing fine rock dust on your windscreen and clearing it with the wipers -- you end up with thousands of tiny scratches in the glass. And that's glass, which is more resistant to such scratching than the materials from which solar cells are made.)

You would also have to design your solar cell surfaces so that they have no cracks or crevices, and nothing that protrudes up above them -- they would have to be very flat, smooth surfaces. Ever seen a solar cell array? They're not all that smooth -- and making them smooth would probably add weight, too.

I think the best dust-clearing device you could come up with would be a small compressor that takes in Martian air, compresses it into a bottle, and (when you need a cleaning) is commanded to blow the air out through vents positioned to duct it across the arrays. Or perhaps just a bottle of compressed CO2 instead of the compressor. A compressor would let you clean your arrays as many times as you want over the lifetime of the vehicle, while a pre-loaded CO2 bottle would only be good for "X" number of cleanings.

But Doug is right -- such a system would likely weigh as much as one of the major sensor packages you want to put on your probe. So you either have to 1) accept the sacrifice of one of your sensors, or 2) increase the mass you can land on the surface by *just* enough to include your cleaning system. Since the second option makes the whole mission more expensive, you'll probably end up getting stuck with the first.

And while you're deliberating on solar cell array cleaning systems, you have to face up to the fact that any solar-powered Martian lander could have its power cut down to below-survival levels by a planet-wide dust storm, whether or not you can clean the arrays. If a really energetic global dust storm occurs and the atmospheric opacity increases beyond a given level for too many sols, a solar-powered probe may simply die. And you've sacrificed your sensor for nothing.

So I'm inclined to agree with Doug -- for longer-duration missions, RTGs are the way to go. For shorter-duration missions, solar power without array cleaning is acceptable, since you're going to get your primary science return very early on. Besides, it seems like Mars is willing to provide enough wind to clean off solar arrays at frequent enough intervals to make extended missions for even these short-duration probes more likely.

There are ways of "tweaking" solar-powered probes, though, to try and get the longest life out them. For example, I believe the MERs use tiny radioisotopic heaters within their main "boxes" to keep the electronics and batteries comfortably warm. Those provide heat without using electricty, thus reducing power consumption needs. The MERs only have electric heaters in places where you can't easily use a passive heating system, like on the IDD. I'm sure there are other ways tweak solar-powered landers to enhance their lifetimes that are both easier to implement and weigh a lot less than solar array cleaning systems.

-the other Doug

No, not impossible -- but such life would have to have developed protections against the radiation environment that would make it vanishingly close to impossible that any terrestrial life form *not* adapted to the radiation environment would be capable of competing with it. Or even capable of surviving.

I always liked the way Mike Collins referred to the extra-terrestrial contamination issue. Of course, he was referring to the remote possibility that lunar materials might pose a threat to the Earth's biosphere, but his remarks apply here, as well.

Collins said that if you take the possibility of a profound threat from contamination by extra-terrestrial organisms (very, very small) and multiply it by the potential damage such contamination can cause (very, very large), you come up with a reasonable number that defines how much attention you give to the problem.

Now, when we start sending probes to dig more than a foot or two into the Martian soil, I think we need to take special care to sterilize any part of the spacecraft that reaches into a realm where terrestrial organisms could survive. But until then, I think the present sterilization procedures (which make the possibility of carrying significant amounts of terrestrial life to Mars very, very unlikely) makes the first part of Collins' equation a very small number. As long as that number remains very, very small, I think the risks of continuing to explore the surface of Mars are acceptable.

Besides, unless we're willing to take the risk, we'll never know whether or not there is any Martian life that needs protecting. Like I said, observing something affects it. And human technology is not infallible, so it is impossible to guarantee that all Mars landers will be *completely* free of terrestrial organisms. You *must* risk some small contamination possibility just to find out if there is any Martian life out there that could be at risk. If you insist on the presence of Martian life, and if you further insist that even a single bacteria carried to the surface will *definitely* contaminate or even destroy that life, then you're forced into the position that we must immediately cease *all* exploration of Mars. Including orbital exploration (since orbiters eventually crash). And you have to admit that your worst fears must already have been realized, since we've already landed and crashed imperfectly-sterilized craft on Mars.

Since we can't even *guess* at where life might presently exist on Mars, or under what conditions it may flourish, we have to do a lot more exploring there, including many more landings and even sample-return missions, to *ever* expect to find it. If it exists. Insisting that even the *possibility* of life on Mars means that we must stop *all* possibility of contaminating it means that we'll never, ever know if that life exists or not.

The most important thing about finding life on other worlds is to see if it organizes in different forms and with different chemical compositions than life does on Earth. If we dare not even go look for it, we'll never have the opportunity to even ask those questions, much less expect to get answers.

-the other Doug

Well, yes -- introducing strains of bacteria that are more successful than native Martian bacteria, up until the point where you've learned as much as you can from the native stuff and preserved it in laboratories and protected zones, is not a good idea.

But consider -- it is really, really unlikely that present-day Martian bacteria live anywhere near the surface of mars. Especially not near enough to the surface for any of the chicken-scratchings our probes have made to get anywhere close to it.

It's been mentioned that the real threat would be for terrestrial organisms to find nutrient-rich environments (which, I will add, must be protected from the surface radiation environment) and overcome any native forms. And I ask, with all sincerity -- just where would one find a nutrient-rich and radation-protected environment near enough the surface of Mars to allow terrestrial bacteria to move from a landed probe into them? And remember, the radiation environment at the surface is a pretty good sterilizer -- any transport mechanism you postulate would have to figure out how to get terrestrial organisms to the protected environments quickly, before the radiation environment destroyed them.

I would be fascinated to hear about any theories of such a transport mechanism that don't depend, at some point or another, on the infamous "and then a miracle occurs" step in the process...

-the other Doug

The problem is that FBC broke down well-funded multi-billion dollar missions into several quarter-billion-dollar missions. And while it may seem to be less of a PR disaster to lose a quarter-billion-dollar mission than a three-billion-dollar mission, people don't have long memories. And losing a quarter of a billion dollars worth of planetary probe sticks in the public's craw as a waste of money, regardless of the fact that the money has paid for continuing growth and expertise within the aerospace community, and is mostly spent back into the economy by the engineers, workmen and companies involved in the project.

The MERs are a good example of a mission that was well-enough funded but mounted just a little *too* fast. Most of those involved in the design, testing and fabrication of the MERs and their various systems have gone on record saying that they worked themselves into the ground getting ready for the launch date, and really could have used another year to prepare. Steve Squyres said outright that one of the most important lessons learned was that, even though they were lucky and no major problems surfaced during the flight, the MER development schedule should *not* be taken as a baseline for planning future missions.

-the other Doug

The simple act of observing something changes it, to a greater or lesser degree. That's an immutable fact of the Universe (and is inherent in the very fabric of a quantum Universe).

You know what always tickled me? The fact that several of the Apollo missions included lunar atmosphere detectors in their ALSEP packages. And what did they find? They found that 99.9% of the Moon's atmosphere, at the time the detectors were active, was composed of the exhaust gasses from the most recently landed LM, the oxygen vented from the LM cabins prior to EVAs, and the water vapor and oxygen that escaped the PLSSes and suits. (A single J mission, if I recall correctly, was said to have trebled the *entire* atmospheric content of the whole Moon.)

In other words, the only really detectable atmosphere on the Moon was what we put there.

So, yes -- take reasonable precautions. But recognize where reasonability ends and zealousness begins.

-the other Doug

Ah - AH!

Makes perfect sense...



-the other Doug

OK, so let's see, I write to Nature and ask to purchase a copy to read the early MER findings.

They write back, telling me I need to buy a year's subscription.

I try to buy a year's subscription, and they tell me that they are an industry-specific publication, and I must *prove* that I am in a field that requires a subscription to their magazine...

I don't know for sure that Nature would follow this policy, but I *do* know that AW&ST does. As do several other periodicals that publish results from NASA probes.

Tell me I'm doing something unethical trying to get access to something that *I have paid for* (with my taxes) when the publishers, when I offer them money, refuse on the grounds that I don't buy the products their advertisers are advertising... at that point, I say that the publishers are acting unethically and any distribution "behind their backs" is not only justified, they asked for it...

-the other Doug