Wednesday, February 17, 2010

Thoughts on NASA and the near future of space exploration

I posted the following reply in the NASA discussion group on LinkedIn. The original post was soliciting thoughts on the changes in priorities for NASA in response to the president's budget request.

The Constellation program was canceled because this administration was unwilling to continue investing many billions of dollars a year to develop a whole new launch capability that would not be ready for 7 to 10 years. For this investment, we would get two new rockets that would never have a very high flight rate, and thus would be extremely expensive to operate. That high cost of development was literally starving many innovative science and engineering efforts currently underway, or planned for the near future. The high cost of operations would mean that this situation would continue into the indefinite future. This was a bargain that this administration was no longer willing to make... not when there appeared to be a viable alternative.

This alternative has just as much of a chance of success as the Constellation program, but also requires much less investment and has the potential to offer much greater capacity and redundancy to the US spaceflight capability. NASA is getting a net increase in budget, and the freedom to spend it on actual innovative research and development projects. Some of this research will vastly improve our ability to carry out long duration spaceflight missions, while other research would dramatically improve our understanding of the Earth, and our environment.

As for science on the ISS: The president's budget actually extends the life of the station until at least 2020 - further improving the chances of doing useful science on the station. The SpaceX Dragon capsule is being designed to provide a significant amount of down mass capability for the ISS. Although the Cygnus transport will not initially be able to support this capability, Orbital has made some encouraging remarks regarding their plans to upgrade the Cygnus craft to have reentry capabilities. The ESA has also made similar comments about their ATV modules.

I agree that our backs are up against the wall with regards to the ability of the US to independently access space. But perhaps this sense of urgency will prompt more commercial providers to finally step up to the plate and start investing their own resources in developing this domestic capability - with an appropriate amount of assistance and investment from NASA. However, at the same time, NASA has to back off a little bit and let them develop these systems to the best of their abilities.

No one is suggesting that we immediately start putting astronauts on these new vehicles. (Not like they did for Mercury, Gemini, Apollo, and Shuttle, and what they were planning on doing for Orion.) From what I've heard, each new entrant and each new system will have to be proven out over a number of unmanned test flights and/or cargo flights before NASA will consider using them for human transport. This seems both fair and prudent.

Will it be dangerous? Yes. Will their be risk? Yes, of course. There always has been and their always will be. However, if it's an endeavor worth pursuing, then you do you best to mitigate the risk and to plan for all of the contingencies that you can imagine. In the end, though, you have to accept the whatever risks remain and just fly the vehicles that you have.

There will be failures, but we will learn from them. There will be deaths, but not by anyone who wasn't fully aware of the risks. They will choose to go, and when they fall, there will still be others lined up waiting to go. For them, it will be the chance to pursue a dream, and the opportunity to push back the boundaries of science and exploration. If you build it, they will most certainly come.

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Friday, February 05, 2010

Google Calendar for The Space Show

For those of you out there who happen to follow The Space Show, with Dr. David Livingston, I've set up a Google Calendar with names and dates taken directly from The Space Show newsletter. This link will take you to a navigable calendar interface. There is also a link in the lower right corner which should allow you to add the events on this calendar to your own Google Calendar view (if you have a Google Account). You can also add individual events by clicking on them and selecting 'add to my calendar'.

I'm going to try to keep up with this on a weekly basis. If anyone notices me slacking off, feel free to drop me a reminder.


Friday, January 29, 2010

The Space Show - John Powell

I made a brief call in to The Space Show with Dr. David Livingston on Tuesday night. The show's guest was John Powell of JP Aerospace. I almost missed the show, but managed to catch the last half hour. I plan on going back and listening to the show in its entirety when I have a couple of hours to spare.

I have been following the progress of JP Aerospace for about ten years now, and I have to say they have come up with some very imaginative concepts that will be amazing technological feats if they ever come to pass. For example, their stratostation concept involves lofting a huge lighter-than-air platform to about 140 thousand feet. This station will serve as a near-Earth observation platform, as well as a possible communications link, an astronomical observatory, a scientific laboratory, and probably dozens of other uses which haven't even been thought of yet.

One proposed use for this station is a point of departure - a harbor if you will - for another one of their concepts, the airship-to-orbit. This is an enormous V-shaped lighter-than-aircraft which might be able to reach orbit by gradually accelerating to orbital speeds over several days. Using primarily buoyancy and aerodynamic lift to overcome gravity losses, this mode of reaching low Earth orbit could have a profound impact on how we think about getting off this planet - at least as much as the space elevator, and potentially much sooner.

My question had to do with the propulsion systems on the proposed airship-to-orbit concept. I've been thinking about this problem for a while. The concept is simple, but the physics are hard. Let me try to explain.

In order to accelerate from approximately rest with respect to the Earth's surface (and about 100 thousand feet up), the airship must accelerate to orbital velocities, which are on the order of 7-8 km/s, and orbital altitudes which are way above 330 thousand feet (~100 km) that marks the semi-official boundary of space.

There are several physical constraints which must be overcome when trying to reach orbit with an airship. First, it must have sufficient thrust to overcome atmospheric drag during the early part of its flight. If you can't overcome the drag, then you can't accelerate. The drag increases with velocity, linearly at first, but later exponentially. Once the thrust and drag are equal, you've reached a sort of terminal velocity. The only option is to fly higher where the density of the air is less, and therefore the atmospheric drag is less.

Second, until the airship reaches orbital velocity, there must be some way of providing lift to overcome the gravity losses. In other words, to keep the ship from losing altitude. During the early part of the flight, this is mostly accomplished with buoyancy and also any aerodynamic lift which might be generated by the airship (which looks like two huge wings stuck together in a V-shape). However, as the airship climbs higher - to get out of the denser air dragging on the ship - the effects of buoyancy and lift are diminished. Mr. Powell confirmed for me that above 300 thousand feet, buoyancy and lift effects are practically negligible.

Unfortunately, by the time the ship reaches 300 thousand feet, orbital velocity has not yet been obtained. Therefore, there must be some other means of supplying the lift required to overcome gravity until orbital velocity and altitude is reached. Thus my question to Mr. Powell was something like this: What kind of propulsion techniques are you considering which will have sufficient thrust to both overcome aerodynamic drag during the early part of the flight, and also provide lift during the later part of the flight, while still being efficient enough to accelerate for days on end without requiring enormous amounts of propellant? His response was that they are working on form of hybrid ion/chemical based engine with a theoretical ISP of around 900 seconds.

I'm still not completely convinced that this approach is viable with existing propulsion technologies. However, I think I now have enough information to do a slightly more detailed analysis of the airship-to-orbit concept. If I can find some time to actually crunch the number, I'll post my findings here.

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Monday, August 10, 2009

Free at last... now what?

Now that I am finally finished with the dissertation, I find myself with considerably more free time. As my wife has recently pointed out, I have a rare opportunity now to pick up a hobby before I allow myself to get bogged down with the next project or any of life's other pressing demands on my time. So, in addition to spending more time with my kids, and possibly doing little light blogging from time to time, what else could I be doing that I would enjoy and still fell like I'm making good use of my time.

One of the things you learn while getting a PhD is just how little you know out of all that is possible to know. I feel that I've learned a great deal during my studies, but there is a great deal more that I want to know... that I need to know. So, I find that it is time for me to leave the sheltered halls of academia and to try and make my way in the real world. I'm ready to put my hard earned education to work, but I am fully prepared to have to learn more in order to do so.

Power and propulsion are two topics that I love to ponder, but I don't think I'll have the resources to start tinkering with actual hardware for some time. If I'm extremely lucky, I might be able to land a job with one of the new space startups, where I'd be able to do that kinda thing as my day job. I'd jump at the chance to work with the likes of SpaceX, Blue Origin, XCOR, Masten Space Systems, Armadillo Aerospace, Ad Astra Rocket, or Scaled Composites.

I've also been wanting to get more seriously into robotics and astronomy for long time now. I have some brief experiences with both of these, but I'd like to be able to advance my skill set to the next level if possible. I often find myself thinking about better ways to interface to tele-operated devices. If Jeff Hawkins is correct about the hierarchical organization of the brain, then it should be possible to build a robotic system which can learn some basic, low-level behavior in response to commonly encountered stimuli, but still be able to pass on unexpected or novel information to a higher cognitive level (possibly a user). Specifically, I'm thinking about robotic telescopes which will be able to scan the sky autonomously, but be able to direct their attention to more novel phenomena based on their own past experiences.

One project that I've been putting off for a long time now (because I couldn't justify spending the time on it with the dissertation hanging over my head) is to look into doing more sophisticated mission prototyping using the spaceflight simulator Orbiter. Although the development of the main program seems to have stalled, there is still an active community of third party developers generating fresh and interesting add-ons for the simulator.

I have been contemplating a building rapid prototyping tool for designing rockets, RLV's, and other spacecraft. The program would be similar to NASA's Rapid Aircraft Modeler (RAM) that I worked on a few years ago. One simply selects from of list of standard components, then resizes and repositions them to rapidly assemble a desired configuration. Then, I would have the program output the necessary files to fly the model in Orbiter. By making use of some of the advanced modeling capabilities provided by the Orbiter API, it should be possible to get a fairly reasonable approximation of the vehicle's performance for a given class of mission.

And one final thing which looks like it will have to be a hobby since I can't seem to get my supervisor interested in letting me do it for work. I've recently managed to get CUDA installed and running on my laptop. I'd like to teach myself how to program the GPU. There is a lot of potential computing power tied up in those little chips, but not all computations scale equally well on the GPU. I think this is probably something that I will not truly be able to appreciate until I learn it through trial and error. Still, there's at least one instance of someone doing discontinuous Galerkin simulations on the GPU with encouraging results. I'd like to see if I can manage to get at least part of my DG solver running on the GPU.

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Sunday, August 09, 2009

And it's official..

The day has finally come at long last. I am now officially Eric M. Collins, PhD.

It has been such a long and arduous process that I'm finding it difficult to accept that I'm actually done. From the perspective of fulfilling a life-long ambition, it was well worth it. Now we will see if it was worth the delay in getting a real job and postponing all of those other things that grown-ups with a decent income get to do.

While I've still got a lot of work to do and papers to write, I also need to focus on looking for a job. I have until the end of the year to find something. I would very much like to get on with one of the new-space companies (e.g. SpaceX, Blue Origin, etc.), but I will also be looking into NASA and some of the national labs. If there is anyone out there who wants to hire a computational engineer with an intense interest in enabling technologies for exploration and exploitation of the space environment, please feel free to contact me.

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Sunday, July 19, 2009

Turbo pump ASCII art

In a comment to a post by John Hare (Told You So - Seleneian Boondocks), I tried to post an ASCII art depiction of a turbo-pump configuration which I thought would better illuminate the point I was trying to make. Unfortunately, the reply window only allows a subset of the HTML markup and decided to severely mangle my ASCII art instead. It really was a good rendering, so I'll post it here, just in case anyone else is curious.

||^ ^||
|| __ _____ __ ||
||^|__| V |_____| V |__|^||
|| < :=======| |=======: > ||
||____| V _|^|_ V |____||
|_____| |_| |_| |_____|
V |^| V

What you are looking at is the bottom of a proposed thrust chamber analog. High pressure gas is being fed into the chamber and forced down and out ("V" in the diagram) through a turbine blade. The blades are hollow, which allow them to act as a pump (through centrifugal acceleration). Water is then pumped into the chamber through a diffuser along the paths marked by ("<", ">", and "^").

As I mentioned in the comments to the other post, the key to making this design work is minimizing the amount of drive gas which gets leaked into the pump chamber around the ends of the turbine blades. Just as the water within the blades is going to want to be thrown outward, so will the gasses escaping through the blades themselves.

Anyway, before I reveal just how much I don't know about turbopump design, I better just quit now. Feel free to comment on this here or at the original post.

Saturday, March 14, 2009

We industrialize!

Now this is the kind of space advocacy that might actually have a chance of appealing to ordinary folks.

There are none of the supposed "justifications" for the space program that NASA contrived a couple of years ago. There's simply a catchy tune, some simple graphics, and a message. That message is that space offers a tremendous opportunity for us to put our ingenuity and productivity to work towards creating a new and innovative economic niche. This niche is one that has yet to be exploited, has tremendous potential for future growth, and one that we appear to be in a rather unique position to take of advantage of at this very moment.

What will we do with this opportunity? Will we continue to throw good money after bad at sectors of the economy which have failed to generate enough wealth to sustain their own activities? Or do we take bold new steps to generate new industries and new services that will form the basis for the next century of economic growth?

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The ISS as fuel depot testbed

I've been wondering for some time if the ISS could be used to advance the technology required to perfect propellant depot technology. It seems that nearly all of the required hardware is already on board the station. The current ECLSS on the ISS electrolyze waste water and condensate to generate breathable oxygen, with the excess hydrogen being vented to space. If the hydrogen stream could be diverted into a Sabatier reactor, then CO2 could be scrubbed from the atmosphere and turned into methane fuel.

I've also been wondering for if a propellant depot infrastructure should be resupplied with pure water rather than the cryogenic fluids. The favorable density and handling properties of water as opposed to LO2/LH2 would appear to make it the better choice for transporting aboard a very simple tanker over potentially long time periods. When shipped as water, the "fuel" can be transported in a non-cryogenic, inert state, and then once delivered to the depot, it can be cracked into O2/H2, liquefied, and stored until it is needed.

Of course, this assumes that your depot has sufficient power and/or time to split water and keep the fuel properly chilled. I found this page which describes the Russian Elektron unit. This article cites a passage from a NASA training manual:


From the “NASA Familiarization Manual on Russian Segment Crew Systems”, Published in 1997.

3.1. Oxygen Supply System
The decomposition of 1 kg (2.2 lbs) of water yields 25 L (0.88 ft3) of oxygen per hour at a pressure of 760 mmHg, which is enough to support one crew member for one day. To provide the daily amount of oxygen for 3 - 4 crew members, 3 - 4 kg (6.6 - 8.8 lbs) of water must be decomposed. Power consumption of the process is ~ 1 kW.

A kilogram per hour at one kW, seems like a very reasonable rate, at that's just for one Elektron unit (if I'm reading this correctly). If necessary, this can scaled up with additional units if sufficient power is available. It may be possible to build even more power efficient electrolysis system if the work of Dr. Nocera at MIT can be turned into a practical device that will operate in zero-G conditions.

If the depot is also crewed, then a steady supply of water would be required any way. The crewed depot could also generate methane as an additional propellant option if the ECLSS included a Sabatier reactor as well as an electrolysis unit. With the exception of the Sabatier reactor and some cryogenic storage tanks, the ISS already possesses all of the hardware. The existing U.S. electrolysis units even have hardware available for connecting to a Sabatier reactor.

So, what would be the point of having the ISS generate and store propellant? Well, first of all, it is currently our only manned research outpost in zero-G. It would therefore be expedient to take advantage of these facilities to work out the basics of cryogenic fluid transfer in micro-gravity. The data obtained from ISS experiments could go along way towards reducing the techological risks associated with propellant depot development.

The ISS also needs fuel for station-keeping. Having the ability to generate it's own propellant would be a nice capability to have. This would also simplify the ISS resupply requirements. Rather than having to deliver water and propellant, each in the individual compartments, only water would be required. The water tanks could be made larger, and therefore more mass efficient. Since propellants would no longer need to be transported (I think hypergolics are currently used), the handling of the payload for resupply missions would be much less hazardous.

Finally, with the ability to produce fuel, the ISS could support a small array of space tugs and transfer vehicles which would service the station and other objects in nearby orbits. For example, imagine that SpaceX puts up a couple of Dragon lab modules in orbits which are coplanar with the ISS. Now imagine that the ISS has a slightly modified ATV docked to it. It might then be possible for an ISS astronaut to use the ATV to rendezvous with the Dragon module and perform any necessary maintenance or repairs.

I have some additional thoughts on how to convert the ATV into a crewed orbital transfer vehicle, but I think I'll save those for another post.

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Sunday, March 08, 2009

A Biological Imperative

Every few months, the debate over humans in space seems to flare up again. The motivations for human spaceflight are usually touched on briefly while reflecting on the loss of the astronauts of the Apollo I, Challenger, and Columbia spacecraft. Sometimes the discussion is sparked by the humans vs. robots debate. Other times it shows up while attempting to justify the human spaceflight budget. Depending on the context and the participants, the discussion can be anywhere from cordial to an outright flame war.

Jeff Foust recently posted a fairly innocuous summary of reactions to the new administration's budget request (Reacting to the budget proposal - Space Politics) which has somehow managed to stir up a fair amount of discussion in its comments. Unfortunately, by the time I got around to reading through it, some of the comments had already began devolving into pointless bickering.

Of course, I felt compelled to post some of my own thoughts. I am reposting them here for my own benefit, and in case anyone would like to discuss them away from the flames of the other post.

Human space exploration is not about science, or even exploration for that matter. These things are a consequence - a side effect - of having humans in space. In fact, science and exploration are a consequence of humans being just about anywhere, including the bottom of the ocean or in caves dozens of kilometers below the surface. Humans will make observations (either directly or through remote probes), form hypotheses, test them, and then find a way to exploit the results somehow. That's what humans do.

The question on everyone's mind is "Why?" Why do we go to all of these extreme places (in person and with probes)? The answer is quite simple: niche exploitation and expansion. It's a biological imperative. We do what biological organisms have always done: expand to fill an available niche, exploit resources where possible, and then search for new niches to fill. In every biological population, there are individuals or groups which make it their purpose to accomplish each of these tasks. Humans are particularly adept at this and are doing so at an unprecedented rate.

What makes humans so special is that they are the first species capable of expanding the biosphere beyond the surface of the Earth. Humans alone are capable of taking this simple biological imperative out into the universe; exploiting the resources found there, remaking the environment to sustain themselves, and always pressing forward. It is for this purpose that the robotic probes are made and sent out in advance; and that robotic machines are being created to assist humans in hostile environments. It is also for this reason that we cannot send robotic probes alone.

In a way these thoughts are complementary to those I have posted previously (Why Space? and Not Just Science). I find that my thoughts have evolved somewhat since then. I have been trying to come to a better understanding of what it is that space advocates are trying to articulate when they give the 'basic human need to explore' argument. Although most space advocates feel this in their bones, they usually fail to give an adequate explanation of this feeling to those who do not necessarily share their passion for space. I'm not saying that my comments above will go much further at bringing this point home to the average Joe. However, I do feel that if we can get past our own personal motivations and cast human spaceflight in a broader context, we may eventually be able to convince others that it is well worth the expense.

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Tuesday, January 20, 2009

Dragon as the new CRV?

In my previous post (A more gentle transition) I tossed out an idea that perhaps a Dragon capsule, launched to the station in support of ISS logistics, could be modified to serve as a crew lifeboat while it is docked to the station. I was quite surprised, then, to stumble across this post (The new X-38/CRV: SpaceX's Dragon?) by Rob Coppinger yesterday, which references this article (Race to the International Space Station begins in earnest) by John Croft over at Flight Global.

I had no idea if such a thing was possible; only that it would make sense to try and use the Dragon for ISS crew-return if dealing with the Russians proved to be problematic in the future. Using the Dragon this way would also remove one of the frequently cited reasons why the Shuttle should not be used to service the ISS beyond 2010; namely that it could not remain docked to the ISS for extended periods of time, and thus could not be used as an ISS lifeboat. But if this story is correct, then there are already studies underway to validate this concept.

The primary difference between this report and my hypothetical scenario is that they appear to be studying the prospect of delivering the Dragon capsule in the payload bay of the Space Shuttle. I guess I assumed that the Falcon 9 would have successfully flown by the time this would be needed. I cannot think of any other reason why they would rather use the Shuttle. If Falcon 9 has been successfully flown by 2010, then it would certainly be cheaper to launch the capsule to the station using a Falcon 9; not to mention the fact that the Dragon is designed to be launched by a Falcon 9.

My other assumption regarding how it might be easy to temporarily convert a cargo Dragon into a CRV while it is docked to the station, may have also been a little too optimistic. There are probably alot of sub-systems that would be present in a crewed Dragon (even a minimal reentry version), that would probably not be found on an unmanned cargo Dragon. If absolutely necessary, a crew could probably ride down like cargo; however, they would most likely want a more robust life-support capacity and manual flight controls available in an actual CRV Dragon.

I have just one more idea, that I'd like to throw out there. I've been thinking for some time now that NASA should get a Sundancer class module from Bigelow and launch it into an orbit near the Hubble space telescope. That way, if anything goes wrong with the STS-125 mission, they would at least have the opportunity to use the module as a safe haven until a rescue mission can be mounted.

Now, there may be another way to add crew rescue capability to STS-125. If they are actually studying the feasibility of launching the Dragon on the Shuttle, then perhaps it would be possible to tuck one away in the back of the payload bay for the Hubble repair mission. Would there be room? Would the Dragon be ready in time? My guess is: probably not, but it's an interesting idea none-the-less.

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