First hand historical accounts can be fascinating. One of the joys of being at the Bell Telephone Laboratories in the day was contact with the folks who had invented much of the modern world - the stories of discovery, invention, implementation and innovation were often spellbinding. But as fantastic as these stories were, I had recently come from an even richer source.
From the late 70s through the early 80s I was doing particle physics at Brookhaven National Laboratories. The accelerator and many of the core experimental areas were run by dedicated groups. Lots of accelerator physics as well as applied physics, mechanical, electrical engineering and computer science. Some of these guys went back to Los Alamos and the first two decades of the cold war. To call the place a rich story environment was understatement.
Details of the Manhattan Project were amazing and shocking. Some of it seemed outlandish at the time, but I've seen it verified as documents have been declassified. These guys were pushing the limits of what was possible and were fueled by science, imagination, often bizarre leadership, essentially infinite budgets and a willingness to take enormous - even life-threatening - risks.
A guy I'll call Tom was a technician on the Multiple Particle Spectrometer. One of those guys who could do mechanical and electrical engineering and make almost anything work. He was bumping into retirement age and loved to talk about the old days. It seems Tom had come from General Atomics and was one of the engineers involved in one of the more unusual projects ever - the Orion Project.
If you are building a rocket, you want to get the most energy possible per unit mass from whatever fuel you are using. Chemical rockets burning a mixture of hydrogen and oxygen are close to their theoretical limit. They work well enough for orbiting stuff in low earth orbit for about $10,000 a pound. Going to the Moon is more expensive and travel through the solar system is expensive and very slow - you are limited to about 150,000 miles per hour even when you play tricks harnessing the gravity of other planets.1 150,000 miles per hour may seen fast, but the Solar System is huge and interstellar space is unimaginably big.
Space is big. You just won't believe how vastly, hugely , mind-bogglingly big it is. I mean, you may think it's a long way down the road to the drug store, but that's just peanuts to space. - Douglas Adams
There are ways around this. Specific impulse is a measure of the efficiency of a rocket. Very loosely it is the pounds of thrust produced divided by how many pounds of fuel are burned in a second. The best chemical rockets have specific impulses of about 450 seconds. Ion rockets produce tiny amounts of thrust, but over very long times and are comparatively parsimonious - they have specific impulses of 3,000 to over 20,000 seconds and would reduce travel times within the solar system.
But we can do better..
To get amazingly high specific impulses you can always use a very dense source of energy - nuclear energy for example. Atomic bombs would have not only specific impulse, but also a very high thrust ... the best of ion and chemical rockets, but with a few pesky side effects.
The Orion project came out of a most unusual paper by Ulam and Reines in 1947. Physics guys (astonishing smart ones), they worked out a "practical" spaceship that used nuclear energy. Although hybrid nuclear rockets that heated a gas were later developed, this was much more dramatic. You open a little door on the bottom of a robust shield on your rocket, toss out an atom bomb, close the door, and set off the bomb.
Freeman Dyson picked up the thread and left the Institute for Advanced Study at Princeton for awhile to work on it at General Atomics. Staggering crazy stuff, but it became a government funded project. It penciled out on the blackboard and the physics worked out just fine.
Tom worked for Dyson and was one of the people who worked on a dynamite powered vehicle that was to investigate stability - a critical piece of the transition from physics to a technology. He described it as loud and frightening - far and away the craziest thing he had ever worked on. Insane and impractical as it is, if we wanted to make it to the next star in under a few hundred years ...
A bit of searching turns up a bit of BBC footage - a must watch!2
There are a lot of things that people can do if they have the will. I'm convinced we could have tackled global warming if we really thought it important (we don't). Because we can't take the easy way out we now are facing the more difficult challenge of sorting out the repercussions - hopefully we'll make the problems for our kids and grandkids a bit more manageable. I'm not quite as optimistic on the this one. It will be enormously expensive.
The trigger for all of this was Elon Musk's Hyperloop announcement. There have been numerous proposals for making use of the right of way for roads, train tracks and even pipelines (monorails for example), and many variants on running trains suspended on air cushions or magnetic fields. Lockheed, MIT and the US Department of Commerce had a project that was to connect major East Coast cities with a levitated tube train in a partially evacuated tube at about 400 mph. It looked really good on paper, but problems cropped up as people thought about the technical issues. Robert Salter of RAND did a lot of work in the 70s on a dramatic underground version (tunneling is too expensive though) and more recently a 1000 kilometer per hour Chinese project based on a modification of an earlier American design.
Elon's need is to reduce air pressure - he talks about 100 pascals or about a thousandth of atmospheric pressure at sea level. A quick back of the envelope calculation shows you should be able to keep a vehicle like his clipping along at 700 miles per hour with about 100 kilowatts of power. That part is enticing. Making a long tube at that pressure isn't going to be inexpensive and one can think of any number of other issues. I certainly haven't studied it deeply, but have issues with some of the cost estimates.
He is a charismatic leader and that is important in getting people lined up behind a project. He is also working in areas much more interesting that helping people consume more stuff. But there are a lot of really interesting projects that can make a huge difference. Many are much more speculative than this (although I would argue his cost estimates are exceptionally speculative) that also don't violate physics , but the potential payoffs are enormous. I'm not convinced fast point-to-point ground human transit over distances of about 500 miles give or take is a central problem. There are other transportation issues much more pressing and there is still optimization to be done in most areas. But my hat is off to him for stirring the pot at bit. I'll be looking at his proposal more critically when there is time. On the surface at the physics level there isn't anything wrong with it, but it may not make sense technologically where issues like human factors, safety, cost and politics rear their heads.
One fact often lost on Silicon Valley is that things like energy an infrastructure are really expensive and slow moving. You don't see a lot of direct invention that is turned into large scale infrastructure. Even something like SpaceX is a re-envisioning of a technology that was largely stable by the end of the 1960s. The innovation is making it less expensive (and that is non-trivial), but the proof of concept existed. It is even more true for the electric car. This is not meant to diminish what Elon has done, but rather to underscore just how difficult the big problems are.
One of the things I like to do is take a January sabbatical of about two weeks to study something I know little about. Fifteen years ago it was telegraphy. I was interested in learning about its social impacts, but also found that physical transport through intranets of pneumatic tubes was a big deal in the day. It still exists in banks and hospitals and the postal service was close to considering it for general mail delivery in the US. (elaborate systems involving thousands of miles of tubing were installed in other countries). We talk about the Internet of things - we had intranets and even some connected internets that moved things more than a century ago.
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1 You can get about 40,000 miles per hour from a chemical rocket designed for this sort of exploration and pick up more using gravity assist by slingshotting off of planets along the way. Basically you transfer some of the kinetic energy of a planet, slowing it down a tiny amount, into the much less massive spacecraft, speeding it up in the process. The record holders are at about 150,000 mph and a bit more is possible.
2 Freeman's son George wrote a book on the subject Project Orion: The True Story of the Atomic Spaceship. I recommend it along with his latest book, Turing's Cathedral.
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Recipe Corner
No recipe, but something that may revolutionize your homemade pizza and flatbread. Steel is a much better heat conductor and storage medium than a pizza stone. You heat a slab for about 45 minutes in a hot (550°F) oven or covered grill and then cook away. The results are fantastic! Rather than having someone cut the steel and worrying about grades, the Baking Steel works very well. If you want to do several pizzas and have something made, you may want to go 3/8 or 1/2" thick, but remember to have the edges beveled to prevent cuts and handle it carefully these are heavy and stay hot for a long time.
These are much less expensive than a dedicated $10k outdoor brick pizza oven, although my hat is off to you if you are serious enough to go that route.
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