Thursday, December 05, 2002

NPRM 02-230

Hollywood is in the process of buying congress and the FCC (as well as other bits of the government). They want rules and laws passed which will give the small existing content cartel control over what people see, so that they can tax and shape the flow of information in our society. Here's the EE Times article. And here's my letter to the FCC:

I oppose NPRM 02-230.

It is unreasonable for the FCC to put restrictions on signals that I can receive. It is unreasonable for the FCC to put restrictions on how I may process a signal.

If content providers wish to deny me the ability to process their signal in any manner I please, they can choose not to transmit, or they can only transmit once we have entered a mutually beneficial contract. If this choice obliterates their business model, that is their problem, not mine, and especially not the FCC's.

The FCC does not have a mandate to sustain the existing business of existing transmitters. The FCC does have a mandate to encourage the development of new technology. Placing broad restrictions on entire classes of processing technology is a subversion of the FCC's reason for existence.

Thank you for your attention to this matter.

Tuesday, December 03, 2002

Hi Def isn't trying hard enough

George Lucas apparently shot most of Star Wars II on a 1920 x 1080 x 3 CCDs x 24 frames/sec. He's been arguing that Hi Def is just as good as film. If you look at 35mm DSLR vs 35mm SLR comparisons, it seems that Hi Def is almost as good as 35mm movie film. But I don't think that's the right thing to compare against.

The DSLR folks like to compare their digital pictures to 35mm film. The consensus: 6 megapixels is close to the resolution achievable with 35mm film, 11 megapixels is maybe a little better. Film has somewhat better dynamic range than the best CCDs.

The Sony F900 (that's George's $80,000 camcorder) has 3 CCDs, so it takes 3 color samples at each pixel location. So does the Foveon sensor in the Sigma SD9 digital SLR, except the Foveon sensor has 3 megapixels. DPreview says the Foveon 3 megapixel is about as high resolution as Canon's 6 megapizel D60. Apply the same scale factor to the F900 and you get a sensor equivalent to 4 megapixels -- about what you have in $700 prosumer digicams today..

35mm SLR film has images which are about 36mm x 24mm, with the short axis aligned to the width of the film strip. 35mm movie film has images which are about 24mm x 16mm, with the longer axis aligned to the width of the film strip. So 35mm movie film has about half the resolution of 35mm SLR film.

Put the two bits together, and the Sony F900 should capture about as much detail as 35mm movie film. But the best movies are shot and printed on 70mm film, with four times that much resolution. Digital sensors with that resolution exist -- the Canon 1Ds has 11 megapixels. The trick, of course, is to get the high-speed readout necessary to take 24 (or more) pictures every second. That requires a differently designed imaging chip.

I think the right spec for Hi Def should be 3840 x 2400 resolution, at 36 frames per second. This will look like 70mm film, and the higher frame rate will eliminate the irritating artifacts that make pans almost unwatchable in American movies. It will downsample to HDTV nicely, but the really interesting display is the PC monitor. 1920 x 1200 resolution 23" CRTs are available today for the price of a modest TV. 3840 x 2400 resolution 24" LCDs are available today for the price of a large HDTV. 36 frames/sec will look good on an LCD, and you can double it to match a CRT's refresh rate.

Curiously, the distribution format for such movies already exists. The pixel stream is about 40 times as fast as broadcast American TV, which MPEG-4 can currently compress into about 1 mb/s. Assuming no improvement in compression, 15 minutes of 3840x2400x36/s would fit on a DVD, and would be playable with an 8x DVD player.

But larger pictures generally compress better, even with no improvement in compression technology. If we suppose that for every factor of 4 pixels we increase the information by 3, then this big stream is about 20 times broadcast American TV, and a standard 4x DVD will supply 30 minutes of it.

Saturday, November 02, 2002


Remember model rockets when you were in middle school? The biggest engines I ever launched were Es. These guys started with Is and ended up using Os.

What strikes me as odd about this stuff, though, is why all these rockets are mainly subsonic. They go transonic or slightly supersonic at the end of the boost stage, but they really aren't getting into the many thousands of feet per second that even suborbital stuff would. And why not? These engines deliver around 200 seconds of impulse, which is a pretty serious amount of bang. If they could get their rockets down to less than the weight of the engine, they should be good for 4500 ft/sec in a vacuum. Surely a few seconds of air drag wouldn't wipe out 70% of this delta V?

What I'd really like to build would be a solid fuel ignited propane ramjet. The idea is to use Kelly Johnson's design for the back end of the Blackbird engine, but with gas pressurized propane for the afterburner and a solid rocket motor instead of the turbojet as an ignitor. Getting proper mixing of the exhaust, air, and fuel might be tough... I think it's significant that those SR-71 motors are so long.

...and you gotta love the web. Georgia Tech has a web-based design tool for just this kind of thing. They call what I want to do a Supercharged Ejector Ramjet. Can't handle a solid-fuel core, but what the hell, let's try a O2-JP5 engine instead.

Work the specs:

C3H8 tank: 5cm dia 100cm long - 1900cc
Energy: 48 MJ
Fuel Mass: 1.1 kg
Solids: 200 seconds impulse, 2 kg fuel
Burn time: 10 sec
Thrust: 392 N (4 G acceleration off the pad)
Delta-V: 294 m/s
Rocket: 6.9 kg mass

Required thrust? 1000 N (about 10 G acceleration)
Inlet area? 45 cm^2
Cowl height? 3 cm
Nose to cowl? 100 cm
Compression angle? 10 degrees
Forebody friction? 0 (uh oh)

Primary Area ratio? 15
Chamber pressure? 6000 KPa (Can't be as high as the swoopy stuff)
Fan pres ratio? 1 (no fan)

Defaults after this...

Thursday, October 24, 2002


One of things that makes HPC (High Performance Computing, i.e. weather, aerodynamic, vehicle crash and nuclear bomb simulation) so expensive is the huge memory systems on these machines. There is an old saying in the field that latency is hard, bandwidth you just pay for. Anyway, the cost of a memory system isn't the memory itself -- Pricewatch puts a stick of 512MB of 200 MHz DDR memory at $137, or $274K for a terabyte. The cost has generally been in the plumbing necessary to connect that memory to the CPU(s)*. You need lots of very fast wires, which has historically required exotic packaging.

Things change. I just read that half of all cellphones are made on circuit boards with enough density to make an HPC architect drool. Chuck the unobtainium and use ALIVH -- this stuff is cheap! It makes me want to design a hobby HPC.

* Well, actually, the prices mostly come from market dynamics. You have consumers (big companies and government labs) with deep pockets and little ability or incentive to ensure they get real value for their money, and producers who try hard to lock their consumers into proprietary hardware and software to avoid real competition. The HPC money well is drying up as (a) defense budgets have been slashed and (b) many customers have realized that racks of commodity PCs will do the job just as well.

Tuesday, October 15, 2002

National Missile Defense

I watched a Frontline program on the National Missile Defense program recently, while waiting to feel tired enough to go to bed.

When Reagan started the Strategic Defense Initiative, the idea was to build a defense against nuclear missiles coming from the USSR. Frontline went over the history of SDI and NMD, but totally missed the fact that the insights and policy turnarounds during those two programs had all happened before. Summary: we've been trying to build ABMs ever since the 1950s. Every time we have a system ready to deploy, either the Congress or the President kills it, and then funds yet another system design. We actually had a working defense from 02-Oct-1975 to Feb-1976, about five months, before that last one, Safeguard, got killed.

Once again, after a few years everyone has realized that defending against incoming missiles is so hard that stopping thousands reliably, the first time, is impossible. Also, the USSR has evaporated. Russia still has the missiles, but we're buying their warheads from them slowly, and they seem less of a strategic threat somehow. So the folks in Washington have changed the emphasis, just as the Johnson administration did in the late 60s. SDI is now NMD, and the idea is to shoot down just a few incoming missiles from "rogue states". They're still trying to do it with "hit to kill" vehicles, basically, hit a warhead travelling 15,000 MPH with another missile travelling 15,000 MPH in the other direction.

Progress so far: since the mid-80s, they've spend $50 billion, they've decided they want to take out incoming warheads by smacking straight into them, but they can't quite hit the target, and they have no idea how to select the warhead from a cloud of decoys bursting from the same missile.

What bugs me most about all this waste is that now that the program goal has been changed, we could achieve that goal by redeploying the Safeguard system we had in 1975! Why screw around with entirely new research and development? I think we should do a cost reduction pass on the Sentinel system design, and then deploy the damn thing and be done with it. Yes, this means I think we should build more nuclear bombs. (The warheads on the Sprint and Nike Zeus missiles are thermonuclear, which gets rid of most of the accuracy and decoy selection problem.)

It would appear that policymakers in Washington have consistently concluded that it is important to do R&D on ABMs, but not important to actually have ABMs. Which makes you wonder if ABMs are supposed to shoot down warheads or keep a bunch of middle class voters in important districts employed.

If you want to find out how nuclear weapons actually work, check the Nuclear Weapons FAQ. It scared the piss out of me. I had previously assumed that nuclear weapons were a bit like a little piece of the Sun, but here. Nope. The Sun is a great big lazy ball of hydrogen with the odd thermal fusion reaction happening here or there. Nuclear weapons operate with an intensity that puts our Sun to shame. I find the notion of forcing reality so far away from it's normal course terrifying to read about.

Wednesday, September 25, 2002

Gas Guzzling

I just got back from a trip to the UK to show my new baby off to all the relatives. The highlight, perhaps, was driving around Northern Ireland with my parents, wife, and daughter, and having my parents point out where they got married, had their honeymoon, etc. I'm entering a stage in my life which is very analagous to the stage my parents were at when I first entered the world. Somehow I can relate better to their experiences of the late 1960s as newlyweds and new parents than I can to their experiences as children. And though getting older does have it's downsides (getting fatter, slower, and creakier), I'm enjoying my relationships with family even more than I did when I was young.

I got a ride in my uncle's new BMW 525d. My wife drives an older 525i, so it's interesting to compare the gasoline and diesel variants. Bottom line: that diesel rocks. Colin says he gets 34 MPG, equivalent to 27 MPG here (their gallons are bigger). Martha gets maybe 22 MPG, and I seriously doubt a new 525i does any better (probably worse: EPA says 18 / 26 MPG).

What I have wanted for a long time is a better minivan: The powertrain should be a 25 MPG front drive hybrid diesel, with electric low-speed RWD for getting around on steep, slippery roads that snowplows haven't visited recently. All I need is 10 HP on each wheel, but I need that at 5MPH. I'd like a suspension and transmission more like the 525i's automatic and decidedly less like that of the Dodge Caravan I have now. The rear seats should stow like the Odyssey, the roof rack should lever over the side so my wife can get skis off the roof, and a dog fence behind the middle seats that doesn't tear up the interior should be a dealer option. Oh, and that roof rack should be good for more than 200 pounds -- I tried putting four kayaks on the Caravan's rack and the thing just sagged down onto the roof!

(For my other car, I want an S2000R. :-))