Selenian Boondocks

I just read today that Selenian Boondocks coblogger, Kirk Sorensen, just stepped down as Chief Nuclear Technologist at Teledyne Brown Engineering to start his own company, Flibe Energy, focused on commercializing his LFTR (Liquid Fluoride Thorium Reactor) technology. Way to go Kirk!

I like the angle he’s taking. While this reactor is nominally a power-generator, he’s looking at the medical isotope and RTG plutonium production markets as additional niches that LFTRs can fill much better than the competitors. I think that’s pretty clever (in some ways like what we lucked into at Altius with Sticky Boom): focus first on markets that your competitors are at a distinct relative disadvantage, use that to get a toehold, and then jump back in to the real fray.

And I thought I had my work cut out for me starting an aerospace company! Good luck Kirk! Here’s to hoping that 20 years from now people look back on Boiling Water Reactors in the same way the look at using leaches for curing diseases in the Middle Ages.

It probably won’t happen too soon, but I give a little heads up on this Altius Space Machines blog post about some depot orbital dynamics work I’m working with a friend on. Hope I have time to talk about it soon.

Nothing to do with space policy or technology, but this has to be one of the most brilliant music videos I’ve ever seen:

Someone actually made a rap video that I not only watched all the way through, but watched again. Alas, the ending seems all too close to reality.

I gave a talk at the Calgary session of TEDx on April 1, 2011 and lunar exploration formed an aspect of my talk, I hope you enjoy it.

…to that other blog I run.

In today’s blog post, I just opened the kimono a bit about our new rendezvous and docking product (the tractor beam I’ve hinted at) and committed to try and do at least one short blog post per day for the next month while we push through a major product development sprint. Should be a wild ride.

I forgot to throw the link up over here, but I put my presentation for the Space Show Classroom up on my Altius Blog. Here’s a link.

[Update: I had a glaring error on one of the slides pointed out. It turns out that an inclined plane in LEO will only line up with an arbitrary departure asymptote once every 360 degree revolution of the ascending node. This means departure opportunities happen once every 50-70 days. Option #1 gets hurt the worst (requiring 4-6 depots to get the coverage needed instead of 2-3), but the other two still have merits. More details later. And I'll eventually update the presentation (or flesh it out on Selenian Boondocks in corrected form)]

Sorry things have been so quiet on my end. With how busy work has been keeping me lately, I have had very little time for blogging, but wanted to let people know that I’ll be joining Dan Adamo (former FIDO for NASA JSC) and Drs. John Jurist and Jim Logan to discuss propellant depots. The show starts at 7pm PDT, and should go for 1.5-2hrs. I’m going to be putting up either a blog post or presentation with some thoughts and notes later today, but for now here’s the link to the Space Show Classroom page for tonight, and for the Listen Live link.

Keith Cowing just posted a link to a fascinating new pro-Propellant Depot analysis. I was impressed to see who the second coauthor was… When you have one of the leaders of ESAS coming out in favor of propellant depots and commercial launch, that says a ton.

Very much looking forward to reading the article. Thanks for the link, Keith!

I’ve been too busy to do much blogging lately, but I just saw this on twitter a bit over an hour ago: XCOR and ULA Demonstrate Revolutionary Rocket Engine Nozzle Technology, and wanted to make some comments.

First off, I wanted to congratulate my friends at XCOR and ULA. This engine work that ULA and XCOR have been doing is something I’ve been watching from the sidelines for some time now, and it’s cool to see them making progress. As Jeff Greason pointed out during and after the Augustine Committee’s work, the US rocket industrial base is in bad shape, and getting new blood and new ideas injected into it is critical.

Second off, I’ve been an advocate of aluminum rocket engine fabrication for several years now. It’s worth noting that while I was still at Masten we ended up doing almost every one of our successful Xombie/Xoie flights using aluminum chambered engines (and I think we’re still the only company to ever fly a reusable rocket engine made of aluminum). Aluminum has a ton of advantages especially for cryogenic engines (ie Methane or LH2 fueled ones), but even for non-cryo ones as well. A quick list includes:

• Low density and high strength-to-weight allows you to get a very lightweight engine without having to push margins or analysis anywhere near as far as with more traditional materials.
• Low-cost and easy availability of many alloys with good mechanical and thermal properties. Once you’ve tried to source a high-strength copper alloy for a medium-ish sized rocket engine you’ll know why this matters.
• Easy, quick, and cheap to machine, even if you want to do tricksy things with the cooling groove geometries.
• There are a ton of manufacturing process options that are semi-unique to aluminum that give you a lot of tools for optimization of the design without excessive costs. Some of these knobs allow you to optimize either for maximum heat flux into the coolant (for expander cycle engines) or minimum heat flux into the coolant while still keeping the wall cool.
• High thermoconductivity (about 50-60% of pure copper’s thermal conductivity) allows you to keep walls cooler–which is kind of necessary with it’s low softening temperature.
• If you can keep it cool enough for long-duration operations (which you usually can for low-moderate pressure engines), thermal stresses can be much lower making it easier to make engines that can stand hundreds or even thousands of cycles

The list definitely goes on from there (like making feasible an alternative engine cycle that I was supposed to have blogged about months ago), but that gives you an idea. The manufacturability/availability issues were enough to get me an opportunity to try them out at Masten, and the work we did for the Xombie/Xoie engines vindicated the choice. For an upper stage engine, the benefits are even more compelling. One of the things I’ve always looked for are manufacturing technologies/choices that allow you to cheat on the cost vs. performance curve. With a small alt.space company, you’re not going to be able to spend the same amount of engine optimization as a bigger aerospace company, so any technologies that allow you to approach “big boy” performance while still being something that a 1-3 person propulsion team can do is worth pursuing.

I think this technology is especially relevant to RL-10 follow-on type efforts like what ULA and XCOR mention they are collaborating on in this announcement. Using the right combinations of manufacturing processes (and there are probably several ways of skinning the cat), you can increase heat flux into the coolant (which allows you to get more power out of the engine or higher chamber pressure), lower the weight of the engine assembly, substantially reduce the manufacturing/inspection/rework cost and complexity compared to a tube-wall nozzle, improve the reusability of the engine, and at the same time allow robust enough margins that a small team can have a realistic shot of delivering a world-class engine.

While I am very happy for XCOR and ULA, I do have to admit to being somewhat jealous that I haven’t had a chance to be involved in this aluminum nozzle technology effort. I spent a lot of time at Masten working on coming up with approaches for making scalable, low-cost, high-performance manufacturing approaches for aluminum nozzles, with just this sort of application in mind, but we were never able to get the sort of outside traction ($$$) it would take to actually validate our concepts (past what we did for the Xombie/Xoie/Xaero/Xogdor engines). Since leaving and starting Altius I’ve been trying to push the ideas even further. In fact, this past month I came up with a completely new approach that if it works (I’d give it about a 75-80% chance of working) could be amazing, not only for rocket engines but also for 3D printing, and many other applications as well. Imagine a process that would make a full-density part with lithium-aluminum strengths, where minimum hole size for internal channels was small enough that you could basically make metal foams, that would allow you to build-in electronic components and sensors, but without the size limitations of most other additive manufacturing processes, which could be scaled up for large thin structures (on the scale of an F-1 rocket engine or an Apollo CSM-sized transpiration-cooled heat-shield).

Anyhow, I hope that some day we’ll get to see some more details on what exactly XCOR/ULA doing for the manufacturing process, and I also hope that we’ll see an RL10-class engine flying some day with an aluminum nozzle (and maybe even chamber). Congrats guys!

occasional blogger john hare

I have listened to some doomsday energy crap (gas $5.00 gallon and more forever, Japanese nuclear devastation, etc) in the last few weeks that started me thinking of alternatives again. It may be possible that one of the solar thermal generating concepts could find funding for terrestrial applications in the current mood. It may even be worth something later on out there.

A turbine engine intakes air and compresses it, heats it, and runs the expanded air through a turbine to extract the energy and run some sort of machine, often a generator. One of the solar thermal schemes has a fairly low pressure gas as a working fluid to do this job. I don’t have references for the original concept. The cool gas runs through a low tech compressor (possibly fiberglass or other in situ material) and then through an enormous solar heat collector before expanding through the (low tech of in situ materials) turbine to generate power. The exhaust heats the compressed gas in a heat exchanger before the compressed gas enters the solar collector proper. The somewhat cooled exhaust then  is sub cooled in shadow or heat sink before repeating the cycle. I think the original was lunar based.

I was unable to insert a cartoon sketch of the concept this time. In raw form, the same sysem using ambient air could be used here on Earth, and could possibly generate some investment or even revenue fairly rapidly in the current energy hysteria. The heat exchanger could be clear visqueen on a roof or hillside with a dark material under it, like shingles or dark rocks. A few leaks would cost energy, but not sleep. The turbine and compressor equipment could be  built from cheap fiberglass, or even wood.  The idea is to build so extremely cheap that efficiency is very secondary in importance.

While this is a bit off topic, it could create some in situ class experience with other peoples’ money, and might even generate a bit of solid rocket fuel of the green folding type for the right company.