Hmmm... upon reading this thread last week, I went ahead and started running SETI processing again. I've got a much better system now than I did back when I ran it a few years ago, and I figured it would be more useful now.

When I went out to the SETI@Home site to download the software again, I got the BOINC client. It's been running fine for me over the past week and a half or so.

So, a lot of people are already using the BOINC client, it would seem. It's sort of a nice name, too...

-the other Doug

I can also really relate to Emily's discussion of writing technique. My natural writing style is rather like Emily describes hers -- long sentences with conversational-tone punctuation. And sentence fragments. For effect.

At least, in my case, there is some sort of switch I can throw in my brain, and I can just start cutting the sentences down as I write them. And I can go through what I just wrote, give it a short once-over, et voila, short, action-verb sentences.

My first drafts are usuallly in final draft or next-to-final-draft shape. I just have this little problem with typos -- in specific, with hitting the space bar just a fraction of a millisecond early. One of the worst examples of this is when I write the short connecting phrase "to the"... it tends to come out "tot he."

Ever tried to use a spell checker to find something like that? When the words "tot" and "he" are both perfectly valid English words? Considering the subject matter I'm usually dealing with, though, I can just do a word search on "tot" and find every instance...

-the other Doug

The only other factor I can think of that could cause geologically recent surface cracking would be isostatic rebound. I know that Mars' axis precesses badly, sometimes pointing 60 or more degrees out of perpendicular to the ecliptic -- maybe crustal deformation caused by extensive solid CO2 deposition as close as 15 or 20 degrees, either north or south (or both) from Meridiani, could have caused the soft, weak beds of evaporite to crack.

The axis precesses over fairly short periods of time, geologically speaking... maybe these cracks are an as-yet-unrecognized result of CO2 "glaciation" encroaching somewhat close to the equator?

I wouldn't think you'd get direct solid CO2 build-up on the equatorial regions themselves... otherwise, I'd suggest the possibility that direct dry ice build-up could have depressed the local surface and caused the visible cracking.

-the other Doug

I dunno -- there is only a tiny little sliver of Home Plate visible in that image, in the far upper right corner. It doesn't look all that much closer to me... we're a lot closer to its elevation, though.

I'm not sure we're getting to Home Plate all *that* soon, though -- there are a *lot* of outcrops throughout this basin area. We also haven't seen all of the Inner Basin yet, I don't think -- at least, not in great detail. I'm still wondering if, just possibly, the dark sands might not be eroding from an unusually dark set of layers that might be exposed in some of these outcrops...

-the other Doug

Aerobraking into low Earth orbit isn't a very good option, either. Effective aerobraking requires you to enter into a highly elliptical orbit and use repeated perigee passes through the upper atmosphere to lower the apogee.

It takes 10 to 20 passes to get into a roughly circular orbit, and even then you need to use some active propulsion to raise your perigee back out of the upper atmosphere.

Most of those elliptical orbits take you repeatedly through the Van Allen belts. Far more slowly than the quick trans-lunar and trans-Earth trajectories (or trajectories to and from Mars or other Solar System objects).

Aerobraking an unmanned spacecraft into Earth orbit would hard enough -- the electronics would have to be radiation-hardened *and* shielded. It would be unworkable to do the same thing with a manned spacecraft.

It might be possible to design a propulsion module -- a taxi, so to speak -- that can aerobrake into Earth orbit unmanned, that carries a CEV-like entry pod. You separate the entry pod on a re-entry trajectory and then alter the taxi's path just enough to put it into its aerobraking course. It can make the few dozen passes needed to brake into LEO, while the crew comes back down immediately. You could then refuel the taxi at a LEO "tender" station, and launch a new CEV to it for your next mission...

-the other Doug

Some of those numbers are a little off, I think. For example, the heaviest payload that a Saturn V ever put into LEO was, IIRC, the Apollo 17 TLI stage (the half-fueled S-IVB, the SLA, the LM and the CSM). That package weighed on the order of 145,000 kg (or roughly 320,000 lbs). Granted, that was a *very* low Earth orbit, a roughly circular 150-km (95 mile) orbit. But it was LEO.

I also think it would be far more helpful to give comparable metrics on each of the launchers. For example, I bet you could easily come up with kgs to LEO numbers for all of them.

-the other Doug

Remember that the air is very thick on Titan, too. Even mild winds have a much stronger erosional impact on the surface than they would if the air were thinner.

-the other Doug

Open to interpretation is right... frankly, I don't see dust devil tracks there. I see wind tails and I see compression artifacts. Note that there are two very obvious dark lines in the image on the right that don't appear on the image on the left -- a sure sign that these are being enhanced out of the noise.

There's nothing of the curly-q type of tracks you see, for example, at the Gusev site. Whatever shown in these images that's true wind effects, IMHO, is from straight-line winds.

-the other Doug

Hmmmm... if escape velocity at the surface of the NS is about .5c, and if the attraction of the BH reaches exactly 1c at the event horizon, then it stands to reason that at some point *outside* of the event horizon, the BH will pull at the NS hard enough to cause some particles to reach escape velocity.

The real question is, how far outside of the event horizon does the BH's attraction exceed the escape velocity from the NS? The curvature of space that close to a BH is extremely sharp -- it's possible that the BH doesn't exert enough force to induce the NS's disintegration until just before it touches the event horizon.

Also, as the NS disintegrates, the extremely dense mass of the stream of matter being sucked into the BH would exert its own gravitational force on the remaining mass of the NS.

What bends my brain is that there *must* be effects on the NS mass that has yet to fall within the event horizon based on the gravitational field fluctuations caused by the mass that has already fallen below the EH. But since Einsteinian physics cannot predict or describe the properties of mass or energy that has been accelerated beyond (or at least exactly to) 1c, it's very, very difficult to gain any insight into what's happening to the mass that falls within the EH, and how its gravitation affects the behavior of the remaining mass as it's swallowed.

-the other Doug

That's what I meant when I said that I didn't think a neutron star would lose its cohesiveness enough to allow significant amounts of matter to be stripped. I wasn't thinking in terms of a solid body that couldn't be broken -- I was thinking of the gravitation holding it so tightly together that the only way anything, including a black hole, could tear it apart would be for the neutron star to barrel into the black hole -- and that the neutron star would be "swallowed" before any significant amount of mass could be stripped.

I say again, I'd want to see what the process of stripping mass off of a neutron star would look like. And, for something as incredibly dense and difficult to break pieces off of as a neutron star, would the Roche limit actually occur inside the Schwartzchild radius of the black hole? My gut feeling is that it would -- the neutron star, I think, ends up getting swallowed whole no matter what you do...

-the other Doug

Well, yeah, a black hole would be the only thing that would have the raw power to strip material off of a neutron star. But I have serious questions as to what the process of such mass-stripping would look like -- it would seem to me that it would be so difficult to get fragments of a neutron star to break off of their parent body that it would tend to retain its cohesion until after it was safely within the Schwartzchild radius of the black hole...

-the other Doug

In a CEV/LSAM lunar mission, by far the majority of power and life support consumables will be in the LSAM. If an Apollo 13-style accident were to happen, there would be little real danger; the CEV/LSAM would just round the Moon and the CEV capsule (with its own power supply and life support, separate from its service module) would bring the crew home.

Of course, if such an accident were to render the CEV capsule itself unfit for atmospheric entry, or if such an accident were to happen on the way home, when they've left the LSAM behind, the crew would be dead. But that would have been the case on Apollo 13, as well.

You really have to appreciate that the CEV itself will not be the "powerful mothership" that the Apollo CSM was, at least not relative to the other modules it will be working with. In Apollo, the CSM was where the majority of your consumables were stored; that won't be the case on a CEV flight. The CEV will only fly alone for short periods; the modules with which it will dock will contain a majority of the consumables for the mission.

-the other Doug

The CEV is basically the launch/re-entry capsule for the Moon/Mars missions. As near as I can tell, even on a lunar mission, the crew will actually "live" in the LSAM (the lander) on their way to the Moon. The only time a lunar crew will have to spend solely in the CEV when they're not either launching, rendezvousing with the LSAM in LEO, or entering the atmosphere will be during the 3-day coast back to Earth.

On a Mars mission, the CEV will likely be "mothballed" for most of the trip -- placed in a powered-down mode with only those systems active that are required to maintain it in an operational state. Rather like the Russians do with their Soyuz craft when they're docked to the ISS (or earlier, when they were docked to Mir) for up to six months at a time. The Mars crews will live in hab modules that will probably look an awful lot like ISS modules -- like the Discovery lab module, in fact -- equipped with the life support, etc., needed to support the crew for the voyage to and from Mars. The CEV and hab module will be attached to a lander and a propulsion module; the whole thing will enter Mars orbit, and the hab, CEV and propulsion module will remain in orbit while the lander takes the crew down to the surface. The crew will again live in the hab module on their return. They'll only power up the CEV and "live" in it again when they approach Earth, and use it just for the entry and landing on Earth.

So, don't think of the CEV as a full spaceship in and of itself. Think of it as a taxi that gets you to and from your *real* spaceship. Except for when they're in the process of getting to and from their real spaceship, the crew won't spend a lot of time living in the CEV.

-the other Doug

Wellll..... except for Viking landers 1 and 2, you mean...



-the other Doug

I've been pondering the fact that Titan's north pole is currently pointed away from the sun. It's northern winter on Titan, and southern summer.

At its distance, does the Sun actually provide significant heating on Titan? If so, what are the phase change temperatures of liquids (mostly liquid ethane, I imagine) on Titan? And do the temperature differences between the shadowed northern pole and the sunlit southern hemisphere range across those phase change temperatures?

What I'm wondering, here (and I freely admit that my thinking is mostly influenced by how water works on Earth and how CO2 works on Mars, each of which may be entirely misleading when it comes to Titan), is whether the liquids on Titan might not migrate to the winter pole and freeze out on the surface, leaving relatively little liquid on the rest of the globe. As Titan passes through its equinoxes, the ices melt and either evaporate or are entrained in the atmosphere as "humidity" and begin to migrate to the pole moving into darkness. During this period, the liquids are more generally distributed through the atmosphere and rain out in a "hydrologic" cycle that waxes through and past the equinoxes, and then wanes as we get closer to winter at one pole or the other. Whenever it's mid-winter at either pole, you get what we're seeing now -- a relatively "dry" environment, due to the freezing-out of the liquids at the winter pole.

If much of the liquid on Titan is currently bound up in a northern polar cap of some sort, we may see indications of a much "wetter" Titan as time goes on and we approach the next equinox.

-the other Doug

First off, thanks to Phillip for his insightful review of copyrights. Don't hesitate to contribute in any way you can, Phillip -- it's great to have all kinds of people here!

Secondly, what I'd love to see in terms of a comparative size display would be something like World Wind or Google Earth -- something that zooms back to show you real, scaled images of all of the bodies we've photographed with any kind of resolution (as far away as the Kuiper Belt or as small as Itokawa). Allow the user to zoom in until they get a good balance between resolution and display, and let them rotate and manipulate each object.

You could even take Steve Albers' maps and project them onto appropriately shaped wire-frame objects -- and every time new images are received and the maps are updated, you just re-project them and, voila, you have a properly scaled Solar System model that updates itself.

I know, I know -- nice idea, but a lot of work. It's times like this I wish I was a programmer.

-the other Doug

And believe me, I was simply proposing a what-if and using the example of the size comparison chart to discuss what *could* be actionable, and under what conditions. I *wasn't* stating that spaceffm stole *anyone's* copyrighted work -- I don't know this Oner's work well enough to recognize anything spaceffm used that might have been copyrighted.

I'm just trying to point out that if you put together something that seems very similar, or almost identical, to copyrighted material, you need to be able to prove that you did the work and you did not use any of the copyrighted material, or else the holder of the copyright on the similar work *might* decide to sue you. I never said anyone wanted to sue spaceffm, and certainly didn't mean to suggest that anyone ought to try.

I would rather see spaceffm stay here in the forum, too... and if I said anything that sounded like I was accusing him of anything, I most certainly apologize.

-the other Doug

When it comes to space stuff, Dan, you're absolutely right. But for poorly-explained schedule and budget overruns on more mundane things, like for example a road construction project, people (at least Americans) are more likely to assume either incompetence or deliberate corruption than c0nspir@cies...

But when it comes to space, the loons really come out of the woodwork. There is something significant, sociologically, in how people become more and more desirous of c0nspir@cies as their world becomes more and more complex, and less and less easy to understand and predict.

-the other Doug

My understanding is that most normal stars can only "build" heavier elements up to the weight of iron. These are the stars that are only massive enough to blow up in a nova.

It takes a supernova, with its resultant temperatures and pressures, to fuse the iron and lighter elements into heavier elements than iron.

The question then becomes: how many supernovae have there been in the galaxy over its lifetime, and how much in the way of heavier-than-iron elements has been created? That would put an upper limit on the amount of high-mass matter that exists, and out of which differentiated, rocky planets may have formed...

-the other Doug

Don't dismiss the value of breaking up a large impactor.

Each year, the Earth is hit by tons and tons of asteroid and cometary material, enough that, if it were to hit all at once, it would cause an impact big enough to wipe out most life on the planet. But it hits in very tiny fragments that burn up before they reach the ground.

If you could blast a relatively small asteroid, like Itokawa, into billions of grains of sand, its impact would not be noticed. Of course, you couldn't reduce the whole thing to such small particles, larger pieces would remain and would make it through to impact -- but they would be a *lot* smaller than the original impactor, and each would have a lot less effect on the ecosystem.

The whole point is to increase the asteroid's surface area. The more of the mass that's subject to ablation, the more of the mass that will simply burn up in the upper atmosphere and filter slowly down to the surface over the following months. And since we already receive thousands of tons of such material every year, that's not really a threat. The remaining several thousand pieces large enough to make it to the ground might cause a lot of local destruction, but (if they were all kept small enough) would be no worse in overall effect than if a few hundred square km were heavily carpet-bombed.

All in all, I'd rather have a few thousand 100-meter craters and the ensuing, potentially manageable destruction casued by them, than have a single 200-km cratering event whose blast effects would wipe out most life on Earth...

-the other Doug

A copyright recognizes any significant value added to an intellectual property.

In the case here, spaceffm put together some very nice comparison murals. But *if* the work of scaling the images so that they were in proper scale to each other was done by someone else (especially by someone who took out a copyright, not on the images, but on the work he did to adjust each image to the proper scale), and *then* spaceffm claimed that he did the work to accurately scale the images, he would be making a false claim. It would be trying to take credit for someone else's work -- work that the someone else spent enough time and energy on, and added enough value to the images' presentations by doing the scaling calculations and manipulating the images accordingly, that he felt the value he added was worthy of its own copyright.

So, if spaceffm were to produce paper copies of these murals and sell them, or even if he were to insist on being credited if the murals were shown elsewhere on the Internet, the issue a copyright court would consider would be whether or not spaceffm had added any significant value to the images, as manipulated and copyrighted by Tayfun Oner. If spaceffm could prove that he did all the work to scale and manipulate all the images in his own murals, then he would win the suit. Just because Oner had made such scaled images doesn't preclude anyone else from doing it -- as long as they do the work and don't just use Oner's pre-scaled images without attribution. However, if all spaceffm did was re-arrange the elements of similar comparison murals made by Oner, without actually doing any of the scaling and image manipulation itself, then he would lose the suit.

In fact, even if spaceffm did almost all of the scaling himself, if he used even *one* pre-scaled image taken from someone else's work and deliberately passed it off as his own work, he would lose the suit.

-the other Doug

Yes, I freely admit the message they're sending may not fall on American ears the way the Japanese would understand it -- it may well be a cultural thing.

But the fact remains that the Hayabusa team is acting extremely hesitant in executing the mission plan, without giving any real details as to exactly *why* they are being so cautious.

I think the more important point is that there is really no detailed discussion out there as to why the Hayabusa team is being so cautious. The USA had the same issue with Viking 1 -- they delayed its landing for two weeks because the original landing site appeared too rough, and they needed to find and validate a new landing site. But the Viking team was very forthcoming with the reasons why the landing was delayed (which was a rather big PR thing, since the original landing was scheduled for America's Independence Day, July 4, and its delay meant a loss of public relations "points" for the Viking team).

All we're being told here is "gee, it's harder than we thought." With no real information as to *why and how* it's more difficult than they thought. And if they won't discuss *why* it's harder than they thought, they invite questions of confidence and competence... at least, in America, they do. In America, if all you say is "gee, this will take us a lot more time and money than we originally thought" without detailing why, people will generally assume that you either weren't competent to do the job in the first place, or else that you've screwed up somehow and don't want anyone to find out exactly how.

-the other Doug

I think this is one of the more telling quotes from the Planetary Society article:

"Hayabusa team is firmly determined to have their job done well to make us trustful of them, but rather because of this the possibility might be high for them not to move into sampling on 19th but try to obtain more information on landing technique to make the landing assurance double sure."

I'm sure this illustrates a big cultural gap between the Western world and Japan, but this says two things to me: 1) The Hayabusa team is far more overtly concerned with "saving face" in the event of a failure than their Western counterparts would be, and 2) because of this, they're extremely hesitant to actually execute the planned maneuvers because of the inherent risk of failure in the way the mission was designed.

If Apollo had been run like this, we *might* have seen a manned landing by Apollo 15, with all previous attempts called off prior to PDI because "we want to make sure the American people trust us to take this risk."

I know it's a cultural thing -- but if you plan a mission that has a number of risky unknowns, you judge the risks as best you can and then you execute the mission plan. As it stands, it "feels" like the Hayabusa team is so worried about the personal dishonor that failure could bring that they're making mistakes by being over-cautious. They're second-guessing themselves, and in doing so they've lost Minerva and one of the target markers. Much more of this and they're likely to lose Hayabusa itself.

-the other Doug

That's what I get for taking 15 minutes to write and edit my post -- Alan got in ahead of me.

Yeah, I thought NH was to be spin-stabilized for most of its flight, I was just not completely sure. Thanks for the confirmation, Alan!

-the other Doug

Ah, the old misunderstanding -- if there's no gravity in space, why worry about mass distribution?

Just because you're in a microgravity environment does not mean that mass goes away. Mass is a constant -- a kilogram of mass is a kilogram of mass, whether it's on Earth and weighs a kilogram or its in deep space and "weighs" nothing. (And no, I'm not inviting discussion of far-end-of-the-bell-curve theories about mass itself changing based on its distance from other large masses.)

Mass works the same way in space as it does on Earth, too -- it takes the same amount of force to overcome inertia in a microgravity environment as it does deep within a gravity field. So, balance is ultimately the same wherever you are, and it's just as important to know the mass balance on a spacecraft as it is on any piece of machinery you're going to be moving.

I hate to admit, I'm unsure whether New Horizons is planned to be spin-stabilized or three-axis stabilized. If it's to be spin-stabilized (which I'm thinking it is), then the mass balancing is even more important. It's exactly like the tire example you mentioned -- if there's a mass imbalance in a spinning object, the object will begin to wobble, and the wobble will reinforce itself until the object flies apart or until other motions couple into the wobble and the thing goes entirely out of control.

But even for three-axis-stabilized craft, you need to know your mass distribution very accurately, so you can place your thrusters in the right places, and fire them properly, to achieve both attitude and translation changes. Especially when you translate (i.e., change your overall path and speed), you have to thrust through your center of mass, and so you need to know your center of mass pretty accurately.

-the other Doug