Well, let's do a little back-of-the-envelope calculating, here, then.

In Carrying the Fire, Mike Collins notes the formula for acceleration G forces -- his SPS engine on Apollo 11 developed about 20,500 lbs of thrust (sorry for the Imperial units, they're what I learned all this stuff in) and when it was used to slow Columbia and Eagle into lunar orbit, it generated roughly one-fifth of a G. Collins set it up thus: 20,500 lbs of thrust is about one-fifth of the total mass of the spacecraft at ignition (something over 100,000 lbs), and so the G force of the acceleration will be about one-fifth.

So, the uprated J-2X engine generates what, about 240,000 lbs of thrust? The heaviest Apollo TLI stage massed, at ignition, something on the order of 317,000 lbs. I have no idea what the current concept is for the mass of the Constellation TLI stage at ignition, but I'd have to guess it in the range of 500,000 lbs or less.

So, at ignition, with a J-2X and a roughly 500,000 lb TLI stage, acceleration at ignition would be roughly a half a G. That would increase to something like two-thirds of a G to nearing a full G by the end of the burn, I would imagine.

It might not be quite as much of a shock as depicted in this excellent CGI animation, but still -- it's not trifling. The best analog anyone has experienced would be the Gemini flights in which the Agena main engines were ignited while docked. Those crews hung on through one-G eyeballs-out burns, plastered to their straps. And no one ever complained.

-the other Doug

At the risk of resembling the 600-lb gorilla in the room, by what mechanism do we see water ice sublimating away out of the shadowed bottoms of trenches and yet putatively accreting onto the landing leg structure? If the temperature and pressure are such that the water ice will sublime in the shadow of a trench, I would think that just being shadowed under the lander wouldn't change the conditions enough to not only prevent sublimation, but encourage deposition.

I'm more inclined to think that the two images are basically identical, the later one with a far different lighting angle that highlights every little lump and bump of dirt blown onto the structure during the landing.

-the other Doug

"Music by Evolved Gas"???

That would be a GREAT name for a band!

-the other Doug

Well, no wonder the TEGA doors won't open! You have any idea how much a cubic meter of soil weighs???



-the other Doug

I've no idea how prevalent the practice is today. The episode I related happened in the early 1990's.

-the other Doug

So... when are we going to start seeing some *deep* trenching?

I'd think that we'd need to first remove the upper regolith from a reasonably large patch and then start working on digging directly into the ice substrate. If we ever want to get ice samples into TEGA and WCL, we'll need to be working directly in the ice layer, I would think.

So far, I've not seen anything deeper than down to the very top of the ice layer -- we hit it and then we go off to the side. I grant you, it may not be easy to dig through the ice layer, but from the looks of things (and someone correct me if I'm wrong), it doesn't look like we have yet even tried.

-the other Doug

Well.. at one point, someone did conclude that, with a little modification, you could put a civilian Salyut station *inside* the Shuttle's cargo bay and launch it into orbit that way.

Gives you some perspective, doesn't it?

-the other Doug

Gee -- since when does an American facility observe holidays like Europe does? For the July 4 holiday, I get that day off, July 4. I have to be back at work the next business day, which happens to be July 7th (the holiday falling on a Friday this year).



I sometimes think it must be odd for Europeans to realize that most Americans get a meager total of two weeks of vacation (aka holiday to non Americans) time per year plus anywhere from seven to nine paid holidays (fixed single-event days off). I once worked for a consulting firm headquartered in France, and our branch of that firm lost a lot of employees the day the Big Chief president of the company came in from France, commented that the European offices would be closed for the entire month of July for "summer holiday," and that us Americans were being lazy and "dropping the ball" by not being productive enough to carry the entire company through that period... *grrrrrr*...

-the other Doug

Remember, though, Nick, that Griffin has said that we're going to see a shift away from the Mars program's seeming entitlement to a major mission every 26 months, in order to pay for other exploration initiatives (including outer planets missions).

-the other Doug

Although, you do have to admit that Acme has a very consistent track record -- and that record is, to be frank, abysmal. Therefore, you'd expect the Acme Mars Lander Wile E. Coyote would have to have used would not have gotten Canis Coyotus safely to the surface, much less anywhere near our beloved Oppy...



-the other Doug

I'll breccia anything we can't keep it going much longer, though...

-the other Doug

Oooooh -- a rousing chorus from Alexander Nevsky, anyone?

-the other Doug

I'm imagining pretty much the reverse, Fred. I'm thinking that the springs may have become very stiff in the Martian cold, and they're just not pushing the doors far enough to have them achieve the stable "open" position. In which case, we'd have best luck during the warmest part of the day.

However, if it's not the springs that are binding but the door hinges themselves, it's possible that the metal of the doors has shrunk in the cold, just enough to make the hinges bind. If that's the case, it's possible that, again at the warmest time of day, a good sharp rap on the side of the entire TEGA device might indeed jar the doors open.

Of course, the only thing you have available to produce a good sharp rap is the robotic arm...

-the other Doug

Only if you started out there in the first place.

Also, I have an image of an evolving Solar System that resembles many of the stars-with-disks that Hubble has imaged. Most of these have been in "nursery" nebulae, and the new star is in the process of clearing the smallest gas and dust particles from its vicinity. There is usually a half-spherical "bow shock" effect along the interface between the star's out-pushing solar wind and the dust and gas in the nebula, often defined by the star's trajectory through the nebula.

So -- you have a newly-formed Sol with its accretion disk forming the majority of the Solar System, and a half-sphere shell of bow shock between its solar wind and the gas and dust of the nebula in which it formed. Thus you have accretion going on in two different places, out of two different basic types of materials, one in a tightly planar disk and another along the surface of a spherical area of interaction between the star's violent outgassing and the womb of the nursery that gave it birth.

In such a genesis scenario, I can easily see population of outer system objects being created in spherical shells at various distances from the Sun, remnants of conditions throughout the first few million years after Sol formed.

Again -- I'm not running this through mathematical models. I'm just putting together what I've learned with what I've observed. And while I *do* understand that most current theories still try and keep the genesis of all SS objects as within the accretion disk and discount the possibility of non-planar accretion, I guess I'm saying that my temptation is to describe that thinking as "clinging to" a planar-only genesis concept. I've seen almost nothing in print on the concept of accretion along a bow shock wave in such curcumstances.

In my little gedanken-model, here, I see the current state of the outer System as a depleted version of a young system, which would contain a nice little set of worlds accreted out of a disk and a vast, low-density cloud of "wastage" formed roughly into a sphere around the star. Gravitic resonances from the planar System as well as perturbations by passing stars will have altered it significantly over the life of the System. But my image is still of a roughly spherical shell of only lightly assembled flotsam.

-the other Doug

Speaking of how the uneducated human mind responds to nature, and completely off-topic here, I am strongly reminded of one of the finest speeches in the history of the American theatre:

Their Moon was cardboard,
Very apt to fray.
And what seems scenic in the Moonlight
Might seem cynic in the day.
The play's not done -- oh, no, not quite,
For nothing ever ends in the Moonlit night.
And despite what pretty poets say,
The night is only half the day.
So let us truly finish
What we've so foolishly begun,
For the story's never ended
And the play is never done
Until all of us have been burned a bit --
And burnished by
The Sun!

Introduction to Act II, "The Fantasticks", music by Harvey Schmidt, book and lyrics by Tom Jones.



-the other Doug

Yep -- there are many examples of parallel development of very similar words, the foremost of which is the word for "water" which, in almost all human languages, contains a "wa" sound considered onomotapeic with the natural sound of water running or being poured.

It's fascinating to me how the human mind, in parallel and not influenced by other, similar development, seemed to find a variety of "onomotapeic" stimuli for basic things like the Sun and the Moon. There must be some basic construction in the brain that sees a blindingly bright object in the sky and thinks the sound "so" in one form or another. More specifically, a vowel following an S sound. (Maybe that's because sunlight causes things to dry out and melt, and phase changes of water tend to make sibilant noises?)

-the other Doug

Okay -- let's look at this from the back forward, rather than as a snapshot of "right now."

The Solar System accreted from an accretion disk, correct? Every body that accreted from this disk occupies a pertty narrow range of obliquities, within less than 10 degrees of one another. This covers everything from Mercury out to Neptune. It includes all but the smallest of the asteroids, as well.

Then we find a population of bodies that does *not* fall neatly into that ecliptic plane. What is the most natural conclusion to be drawn from that? The conclusion I draw is that the accretion disk had ceased to be a flat disk by the time we got out that far from the sun. Lack of tidal forces and all that.

So, matter that is still gravitationally attached to the Sun but beyond the forces that draw the matter into a disk -- in what way would it form itself? I would think physics would demand that such matter would arrange itself as a sphere around the Sun. Just as the farther-out shell of cometary debris, the Oort cloud, has.

Now, I will admit that I haven't read each survey. But from the results that get talked about (i.e., the discovery of pretty much any body large enough to have been found thus far), not only are we *not* seeing a majority of these objects in the ecliptic, my understanding is that *none* of the more massive objects have been found in anything except inclined orbits.

What does it say about the general distribution of KBO objects when none of the larger members of that population thus far discovered orbit within the ecliptic? How can that be worked back into a population that has its greatest density in the ecliptic with a population that thins out as you move away from the ecliptic (i.e., a torus)?

This is the logic chain that leads me to believe that the KBO population distribution is closer to spherical than to a toroidal "belt."

As with all things, I could, of course, be wrong...

-the other Doug

Well... some American probes have had names that are more-or-less descriptive of their functions, such as Ranger, Surveyor, Voyager, etc. But others have had far more prosaic names -- Lunar Orbiter, Lunar Prospector, Mars Reconaissance Orbiter, Mars Exploration Rover, Mars Polar Lander, etc., etc.

Yes, a few were given more poetic names (a la Spirit and Opportunity). But I just wanted to point out that we Americans have suffered from a lack of imagination at times, too...

-the other Doug

ISTR my name being on MPL, as well. Wherever it ended up.

-the other Doug

There's one phenomenon we're all forgetting, here. And it surely impacts the possibility of Phoenix's survival upon spring thaw.

You see, as has been noted, the solar panels absorb light. They're very dark. I'd bet you anything that they re-rediate in the infrared -- i.e., like most dark things, they warm up in sunlight more than light things do.

We *know* what happens in the Martian polar spring when the dry ice thins and dark soil or rock patches heat up underneath their icy coatings. The dry ice sublimates from underneath, building up pressure pockets that set up violent structural failures of the covering dry ice layers. That process creates geyser-like dust plumes that have been imaged many times.

During the spring thaw, the dry ice covering the solar panels will warm up and sublimate into gas next to the dark portions of the solar panels.

I'd say it's possible, if not probable, that Phoenix's solar panels will be the scene of local gas-escape explosions in the coming spring.

I'll be *real* interested in seeing what HiRISE shows after a full winter cycle.

-the other Doug

Honestly, if you're hung up on making differentiations, then simply call everything big enough to round itself and that primarily orbits the Sun a planet. Then subdivide into:

Rocky Dwarf Planets: Mercury, Ceres
Icy Dwarf Planets: Pluto, Eris
Terrestrial Planets: Venus, Earth, Mars
Ice Giant Planets: Uranus, Neptune
Gas Giant Planets: Jupiter, Saturn

The only subdivision that is likely to see any change in the future will be Icy Dwarves, of course. And there *is* actually a good argument to be made to remove Pluto/Charon from its subdivision and create a new one, Double Planets, for any pair of objects big enough to self-round which orbit each other around a common point not contained within the surface of either planet. Fact is, we're probably likely to find many other such double planets out in the realm of accretion-without-perturbation (i.e., away from the gravitational harmonics Jupiter and Saturn created in the "main" system).

Heck, this could be exciting -- right now, our own team, the Terrestrial Planets, are in the lead with three! Those Icy Dwarves are on our tail, though, with two and more on the way! It looks like someone's making a move to pass around the outside!

(OK -- so I'm just thinking, if you could get the average NASCAR fan interested in the Solar System, it would have to be a good thing... *grin*...)

-the other Doug

Glad I finished reading the thread before responding, 'cause that's the exact point I was going to make.

You have to remember, everybody, that the Kuiper Belt is a (likely spherical) shell of bodies, not the remains of the originally super-flat accretion disk. We're out past the disk, where accretion followed different rules, and may still be occurring.

That volume of space contains so many bodies in so many trajectories that don't cross each other for billions of years at a crack, that even a gas giant would have a hard time clearing it all out in the 4.5 billion years the Solar System has existed, much less an Earth-sized planet. It's simply a function of volume -- correct me if I'm wrong, someone, but doesn't the volume of the Kuiper Belt exceed the volume of the entire Solar System from Neptune on in? And unlike the "main" system, which occupies a pretty flat plane (thereby limiting its useful volume when discussing neighborhood-clearing), the more spherical nature of the Kuiper Belt increases the volume to be cleared -- well, literally astronomically.



-the other Doug

The only thing we need to be reasonably careful of, landing close to Tranquility Base, is to make *certain* that even if your targeting is a bit off, you don't run the risk of blasting the historic area with rocket exhaust or pelting it with dust blown by said exhaust.

From the various sources that came out of Apollo, I'd have to think that we can model the closest safe distances from the historic site that you can allow overflights (at various altitudes) and landings.

-the other Doug

Danke. In fact, in starting it, I was thinking -- now that we're within days (or weeks at most) from finding out what TEGA and the wet chemistry rigs will find on the subject, it's our last chance to speculate in absence of solid fact.

I find it useful to recap best current theory just before acquiring new empirical data, especially when it's data that we've not been able to collect before...

-the other Doug

I not only agree, I was planning on writing up a post this evening that made that same point. You beat me to it.

With Mars, the IAU decided that since we have additional data, we can make better and more illustrative placenames than were used for the low-resolution telescopically viewed features. Thus mares became plana and planitias, bright points became mons, etc. Some features retain their original names -- Hellas comes to mind.

I still think of Mars in terms of Syrtis Major, Mare Meridiani and Mare Cimmerium, though... and Nix Olympica. More a product of what I learned as a child than anything else, I'm sure.

-the other Doug