Friday, January 19, 2007

Hello? NASA PR?

I finally found the video shot by the WB-57 chase plane of the ST-114 "Return to Flight" launch. It's fabulous. Keep watching, and near the end you'll see the SRB seperation. The plumes from the seperation rockets are huge!

NASA article on the development of the WB-57 camera system


I think this is really compelling imagery, but it's grainy and shaky. Still, it's way more interesting that the view of the three white dots of the engines during ascent. A little postproduction work could stabilize the imagery on this video, and yield something even more fun to watch.

Saturday, January 06, 2007

Tyrannosaurus Regina

My daughter Anya is 4.5 years old. She likes to have me make line drawings of things and then paint them. Today she wanted a dinosaur.


"No, Tyrannosaurus Rex."

I'm no artist, but I did my best, and I was fairly pleased with the result. You know, the strong nose ridge, the gaping jaw filled with long sharp teeth, the massive tail, and the huge talons at the points of the rear feet.

Anya added a crown. "A princess Tyrannosaurus Rex!"

Then she insisted that I add glass slippers.

These things weighed what, ten tons? A great deal of that was the neck and torso musculature necessary to thrash car-sized animals to death. It's hard to overstate how dangerous these things would have been around princes and princesses and folks with chain mail and so forth. The talons on these things could probably punch through an unreinforced driveway.

And then, the glass slipper. The most impractical possible footwear. Like clogs, inflexible. But also prone to shattering, possessing little traction, and probably heavy once made thick enough to be safe. I'm personally certain that the glass slipper concept is due to some sort of mistranslation. But still, how do you apply glass slippers to a Tyrannosaurus?

Monday, January 01, 2007

Organic Photochemistry

Some of you may know that I've been carrying around a wacky hunch about the operation of the brain for several years. Here's the start of the thread in August 2000, and here is my summary of the idea. Ever since then I occasionally grope around for some way to design an experiment to refine or reject the idea.

Yesterday I had a very interesting conversation with a pair of physical chemists. While he didn't get me to an experiment design, he did provide a lot of insight.

First, I had assumed that if the gated ion channels were exchanging photons, there would be a glow that could be measured. Not so. AJ gave me the impression that some photons get produced and consumed in a way that can't be interrupted: remove the consumer and the producer does not emit. As a result, you'd never see a glow. I've read that magnets and charged particles transmit force through photons... somehow those photons must not be observable either.

Next was the biochemistry of light emission and absorption. Apparently absorbing and emitting light requires violent chemical reactions that tend to destroy the molecules involved. AJ said that much of what retinal cells do is regenerate the rhodopsin as it gets smashed. He would expect to see a lot of biochemical infrastructure to handle free radicals and so forth if the brain was producing and consuming lots of photons. And he figures that people would have seen all that chemistry already if it were there (although maybe they weren't looking for it).

And then there was the issue of wavelength. For best efficiency, a long straight radio antenna typically should be one quarter of the wavelength of the signal being sent or received. For instance, a cell phone uses 1.9 GHz signals, about 6 inches long. Most cell phones have antennas about 1.5 inches long, most of which is buried in the cellphone. So I had assumed that rhodopsin, which receives photons from 400 to 600 nm, would be around 100 to 150 nm long. Not so. As this link shows (look at the third figure down), rhodopsin is at most 9nm long. Apparently the coupling of photons to such small structures is via a completely different mechanism. That's a good thing, because I was expecting 12 micron photons, or thereabouts, and cell membranes are three orders of magnitude smaller. This throws a significant wrench into my hunch that the membranes are acting like waveguides.

I had previously computed that the energy from one ion dropping across a gated ion channel was equivalent to a 12 micron photon, which is very deep in the infrared. So, if you wildly assume (in the spirit of this whole thing) that one ion generates one photon, you'd expect to see 12 micron or longer photons. AJ points out that this is a portion of the spectrum to which most organic molecules (and water too, if I understand correctly) are quite opaque. But of course, that might be a good thing. If the ion channels are exchanging photons through waveguides, it's probably best if the photons propagate well only in those waveguides and not elsewhere, otherwise there could be a fair bit of crosstalk.

None of this gets me closer to an experimental design, of course. If anyone has a suggestion for a book that discusses organic photochemistry, I'd love to hear about it.

Combat resupply and rescue

I'm not a military guy, I don't know much about how they do things. But I have read Blackhawk Down, and I have some sense that a casualty is a much bigger problem than one guy getting shot. If there is no well-linked rear to which to send a casualty, a fire team has a huge liability. I think the usual rule is that one casualty effectively soaks up four people. It reduces the fire team's mobility and effectiveness, and can rapidly send a mission down a cascade of further problems. So, I got to thinking about how you could improve combat rescue.

Let's assume you control the airspace about the battlefield, or at least the portion of it above small-arms range. Helicopters work pretty well when you want to insert your fire teams, because folks near the target can often be taken by surprise and the choppers can dump their loads and be off before serious resistance is organized. But helicopters are not a good way to get people back out, because they move slowly near the landing zone and are thus pretty easy targets. What you need, getting out, is a lot of acceleration and altitude, right away. You want a rocket.

The wounded guy goes into a stretcher. I'm imagining something like a full-body inflatable splint: it squeezes the hell out of him, totally immobilizing him, and insulating him from cold and wind. You'd design the thing so that it could be popped in a couple of places and still work fine. The stretcher gets attached to a rope attached to a reel at the bottom of the rocket.

The rocket fires a very short exhaust pulse, which sends the thing up 50 feet or so. At this point the rope is entirely unreeled. When the rope goes taut, the main burn starts, accelerating the stretcher at, say, 5G straight up. The exhaust plume is directed out two symmetrical nozzles slightly away from straight down so that the poor guy at the bottom doesn't get burned. Acceleration drops to 1G for ten seconds or so once the guy is at a few hundred miles per hour, and then cuts out. The rocket coasts to a stop at 10,000 feet or so, at which point a parasail pops out.

At this point an autopilot yanking on the control lines can fly the guy ten miles away to get picked up on the ground, or a helicopter or C-130 can grab him out of midair. A midair grab sounds ridiculous but apparently they already use this technique for recovering deorbited film capsules and they haven't dropped any yet. A midair pickup at 2000 feet would have 8 minutes to snatch a guy falling from 10,000 feet at 16 feet/second, which seems plausible with good communication.

[Update: apparently they already use midair grabs for picking up people, too. They use a helium balloon and snag that. The trouble is that when they winch the guy in, he generally spins around in the vortex behind the airplane, and when he gets to the tail of the airplane he can get bashed against the fuselage a fair bit before they get him inside.]

A rocket sufficient to boost 300 lbs of payload to 3200 meters needs about 300 m/s delta-V. With a mass ratio of 80% and an Ve of 2600 m/s, the rocket will weigh 120 pounds. That's not something you want to be carrying around with you, but it is something that one guy can manhandle into an upright position. So you have to deliver this heavy, bulky thing to a fire team in the middle of a combat zone which is already distracted by tending to some casualties. Luckily, you can make the rocket pretty tough.

I suggest dropping the recovery package (ascent rocket, stretcher, medical kit, ammunition) on the fire team as you might drop a smart bomb. Instead of exploding a warhead, this munition pops a parachute or fires a retrorocket right before impact to minimize the damage to whatever it hits and cushion the blow to the medical kit. Someone on the fire team might use a laser designator to pick the landing spot, so that they have good control over the difficulty of recovering the thing. You'd want to be careful: bomb there, recovery kit here.

I posted about this three years ago in this thread:
Back then I thought you needed the robot paraglider to deliver the recovery package. Now I suspect something more like the smart bombs we already have would be okay.