Saturday, August 12, 2006

More on capturing asteroids

It seems like I read something about this in the news a couple of weeks ago, but I can't find the reference now. Anyway, Centauri Dreams has a post reviewing a paper by Didier Massonnet and Benoit Meyssignac. A Novel Strategy for Asteroid Deflection

Essentially, we capture a near Earth asteroid and park it at L1 or L2. If the Earth is ever threatened by a cometary or asteroidal impact, then the captured asteroid can be maneuvered into the path of the oncoming object to either deflect it or break it up. This is one of those ideas that make perfect sense once you hear them, but it sometimes takes a rather insightful person to come up with it in the first place. It gives new meaning to the old expression "Fight fire with fire."

There are two potential drawbacks to this plan that I can see right away. The first is the propulsive requirements to first capture the shielding asteroid, and then to move it again into the path of the approaching object. Of course these requirements would likely depend on the mass and orbital elements of the shielding asteroid, but I'm sure some kind of lower bound could be computed to give us some idea of the magnitude of effort that would be involved in such a plan.

Assuming, however, that the asteroid can be suitably maneuvered, there is always the chance that introducing a second body of significant mass would just make matters worse. There is always a little bit of margin for error in orbital calculations, and that error gets more significant when massive bodies come in close contact. I'm sure that such a plan would not be put into effect unless it were clear that the intervention were necessary and the outcome, whatever it may be, preferable to doing nothing.

Anyway, the Centauri Dreams post goes on to talk about some alternative uses for a captured asteroid, namely fuel production. As long as you have a massive chunk of raw materials nearby, you might as well make some good use of it.

Personally, I think there are probably a great number of benefits that could be realized from having one or more asteroids in close proximity to the Earth, most of which we haven't even thought of yet. It will be very difficult to establish any kind of significant off-world human presence without having a large amount of material resources readily available. That is why the moon is such an important destination for the near-term future of manned space exploration. There are abundant natural resources available on the moon, the explotation of which will open up vast new possibilities for human activity off-Earth.

Thursday, August 10, 2006

Building a better rocket

Just thought I'd comment a little bit more on this bit of news that I found through a post over at RLV news. Some interesting excerpts from the article.

The NASA-funded research at Purdue focuses on liquid-fueled rockets. Specifically, the work deals with understanding how fuel and oxidizer interact inside the rocket engine's fuel injectors to cause unstable combustion. The instability results in extreme bursts of heat and pressure fluctuations that could lead to accidents and hardware damage.

a.k.a. Rapid Unscheduled Disassembly
"Combustion instability is a complex phenomenon that has hindered rocket development since the beginning of the Space Age," said Nicholas Nugent, a doctoral student in Purdue's School of Aeronautics and Astronautics. "We have to learn more about instability before future engines can be developed and used for space flight. Predicting combustion instability is one of the most difficult aspects of developing a rocket engine."

"The main purpose of the work is to generate combustion and instability data so that other researchers can develop better computational models for designing rocket engines," Nugent said. "We are generating benchmark data that will improve the design analysis of all types of rocket engines."

This work is actually just one small part of a much larger research effort aimed at improving the design and analysis tools available to rocket designers. The research is being conducted by a large consortium of university researchers which is referred to as the Constellation University Institute Program. The specific collaboration that these researchers, as well as myself and my advisor, are a part of is the Thrust Chamber Assembly (TCA) Virtual Institute. The aim of the research is to improve the state of the art in design tools and predictive simulation technology for engineers designing rocket engines.

For many engineering disciplines there exist some fairly reliable computational design tools which are employed regularly by engineers to refine their designs before being required to build and test actual physical prototypes. However due to the extreme environments and the complexity of the many coupled physical processes inside a rocket engine (fluid dynamics, chemical reactions, thermodynamics, acoustics, structural mechanics), it has been nearly impossible to develop similar tools for rocket designers. Consequently, rocket development must rely heavily on emperical models that have been developed through trial and error over the past few decades.

The part of this problem that we, and a few others, are working on is the development of a computational fluid dynamics solver capable of accurately modeling the extreme flow environment inside of a rocket engine. We're talking everything from the injection of cryrogenic propellants to the combustion of the fuel and oxidizer to the accurate simulation of unsteady turbulent high Reynolds number flows. This flow simulation will also be coupled with acoustic, thermal, and structural simulations to create the first predictive simulation tool for rocket designers. However, before we can trust the simulation, our code must be validated against the experimental results being generated by several other research groups. The researchers at Purdue are one of these groups.

In the end, we would like to provide rocket designers with a tool which they can use to determine the optimal configuration of a given thrust chamber assembly. By simulating the performance of their designs before testing them, it should be possible to eliminate many redundant or excessively over-designed features which have heretofore been necessary to ensure the engine will not fail. This could potentially allow the development of a whole new generation of lighter and more efficient rocket engines.

Back in May, I attended a workshop in Huntsville where we discussed the current state of TCA research and near term directions. I still have my notes around here somewhere. If I can find them, and a little spare time, I will try to post some highlights from the meeting.