Wednesday, August 29, 2018

Looking for loft with all the comforts of home

I ran across this post over at the systemic blog about ballooning in the upper atmosphere of Venus and Jupiter. Presumably, there are sweet spots in their atmospheres where the temperature and pressure are close enough to STP at Earth's surface that a human could go ballooning in these locales with little more than breathing apparatus and attire suitable for surviving the climate (an acid-resistant full-body bathing suit for Venus, or a heavy parka for Jupiter).

In the case of Jupiter, however, the post leaves out one important detail: gravity. On Venus, the gravity is comparable to that on Earth. However, if one were to go ballooning among the cloud tops of Jupiter, one would likely spend a lot of time pinned to the floor of the gondola by about 2.5 g's (2.5 times the Earth's gravity).

The article reminded me of a little exercise in orbital mechanics that I had once worked out. I was looking for places in the solar system where one could experience about 9.8 m/s2 of gravitational acceleration and a 24 hour day. In addition to the Earth's surface, I thought that a space station orbiting a gas giant could possibly provide the proper environment. Simply place the center of gravity of the station in a 24 hour orbit around the planet, and extend a pair of tethers up and down from there such that a full 1G would be felt at either end. At the lower end, the force of the planet's gravity exceeds the centripetal force due to the orbit by exactly 1G, and at the upper end the reverse is true.

Let R denote radial distance from the center of the planet, and H be the height above the commonly accepted "surface" of each body. The numbers given below are for each planet around which this theoretical orbiting station could exist.

For Jupiter:
R[lower] = 110385 km
R[orbit] = 288208 km
R[upper] = 1861246 km
H[lower] = 39015 km

For Saturn:
R[lower] = 61187 km
R[orbit] = 192841 km
R[upper] = 1856417 km
H[lower] = 787 km

For Uranus:
R[lower] = 24196 km
R[orbit] = 103222 km
R[upper] = 1854656 km
H[lower] = 666 km

For Neptune:
R[lower] = 26324 km
R[orbit] = 109229 km
R[upper] = 1854715 km
H[lower] = 4024 km

If this same process is applied to the Earth, we get the recipe for a space elevator.

For Earth:
R[lower] = 6363 km
R[orbit] = 42233 km
R[upper] = 1854357 km
H[lower] = 0 km

Curiously, we see that no matter what planet we are orbiting, the upper end of the tether is always at approximately the same radial distance. As I look back at my equations now, I see that there is a weak dependence on M, however the coefficient is exceedingly small. The first two terms of the series expansion are:

R[upper] = 1854336 + M*3.6695e-16 + ...

where R is in km and M is in kg. I'm sure this is probably a well established conclusion in orbital mechanics or general relativity, but it's the first time I've encountered it.



I had a thought recently concerning public engagement with NASA's human spaceflight program. I was puzzling how the Hubble telescope, and the Mars rovers could get such good exposure with the public, and yet the ISS and Space Shuttle, let alone the astronauts themselves are barely acknowledged. I had also been reading a number of articles which described NASA's PR problem as essentially not being able to tell a good story. (We'll assume for the moment that they actually have a compelling story to tell.)

Then it slowly dawned on me. To understand the public's engagement with certain aspects of the space program, just look at how they refer to Hubble, Spirit, and Opportunity. This as opposed to The International Space Station, or the Space Shuttle Atlantis. Or even, The Crew of Expedition 20 to the ISS. Do you see the difference?

The Hubble Space Telescope, and the Mars Exploration Rovers have been successfully anthropomorphized. They have been transformed from mere pieces of hardware into entities unto themselves. We care about whether Hubble is revived and rejuvenated or left to burn up in the atmosphere. We've started rooting for those plucky little probes that just keep on going and going, exploring the places that we fancy ourselves going someday. People tend to imagine that these probes have grit and determination, even if they realize deep down that they are just remotely controlled devices.

And it really is not that hard to do. I believe that humans are at least partially hard-wired to attribute familiar qualities to inanimate objects or even natural physical processes. Consider how the ancient Greeks anthropomorphized the Sun, Moon and planets, as well as wind, rain, seasons, etc. All of these were given the guise of deities, each with their own motivations desires, and emotions. It is this ability to project human qualities onto these inanimate objects that allow us to empathize with them. This empathy moves us to interact more fully with the object. This allows us to better understand it and possibly respond more effectively when its behavior suddenly changes.

What conclusions can we draw from this? Well, apparently it's not enough for a mission to be nominal, and its science output to be outstanding. To be truly successful in capturing the imagination of the public, there has to be some part of the mission which people can identify with. Whether it be an probe, a spaceship, an astronaut, or even the science itself, when the story is told there needs to be something that people can empathize or identify with.

Now, let's see if I can remember my creative writing lessons correctly: To tell a compelling story, you need to have a sympathetic character, the hero, who must obtain something of great value (either in general or personally). Then, there is the journey, wherein there are obstacles to be overcome and problems to be solved along the way. Then, there's the climax where the goal is within reach. And finally, the resolution; where the hero either gets what he is after and/or realizes something more profound after having made the journey.

Nearly all of our spaceflight endeavors have all of the elements of a good story. Unfortunately, we have not had very many good story tellers. Just off the top of my head, the ISS is an excellent story waiting to be told. It's more than just a place. The ISS is the realization of an epic quest to establish a foothold among the stars. It's very existence is a testament to the imagination, ingenuity and dedication of humanity. That what it wants more than anything is to be allowed to fulfill its potential as a research station, and a way point to the stars for humanity. It is a port of call (come on people, think Babylon 5).

ISS-alpha has been on a journey from concept to reality for thirty years. Her birth was tricky, and she has grown quickly throughout these first twelve years of life. Now, she is nearly fully grown and ready to start a useful and productive life. But wait, there is still trouble ahead. There are those who would see her fail, even now. Those who would starve her of the resources she needs to stay aloft and to care for her human crew. Those who do not recognize her true potential to do great things for humanity.

Will ISS-Alpha be allowed to continue on her quest? Will she be allowed to continue caring for her human crew? Or will the short-sighted bureaucrats deny her the opportunity to prove her worth? Will she be destroyed in a flaming death when she can no longer keep herself aloft? What lessons have we learned from ISS-Alpha while following her on her journey? What more is there that she can tell us by allowing her to continue?

People are not always rational. They make decisions based on what they feel is the right thing to do in any given circumstance. I've heard several times that we could have built and launched an improved version of Hubble for less money than we've spent in the various missions required to upgrade and repair it. Meh.. Maybe, maybe not. But if we were to do that, then they would be just another bunch of satellites, like a Chandra or Spitzer. They will continue to produce great science through out their useful service lives, but when they eventually fail, they will have no chance of redemption.

If we really want to reach out to people beyond our narrow circles of fellow space enthusiasts, we have to learn how to tell a compelling story about all of the great (and not-so-great) things that are happening. We have to tell the story in such a way that people actually start caring about what happens next. They need to be engaged to the point where they can't help themselves but to imagine what it must be like. If we tell the story right, then our audience should be able to come to their own conclusions and actually form their own opinions as to what they think we should be doing in space. Whether these opinions are good or bad, they will at least have them and will be prepared to make an issue out of it if it happens to come up in conversation in the future. This is the kind of engagement we need to get from the general public.

So, I will be rethinking how I relate to ongoing and future space missions. I want to engage them on a more personal level, but more importantly, I want others, who don't normally think about these things, to be inspired, or outraged, or something.. anything.. except apathetic. Because I've been apathetic. Not about space, but about enough other things to know that there is nothing more frustrating than feeling like there is nothing you can do that will make a difference, especially when we really need to start making a difference.

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Wednesday, June 01, 2011

Notes from ISDC 2011

ISDC 2011

The National Space Society hosted the 2011 International Space Development Conference in Huntsville, AL from May 18-22. Since it was so close, I decided I couldn't pass up the opportunity to hang out and network a bunch of fellow space professionals and enthusiasts. I had only attended one other ISDC prior to this one, in 2007. That conference was pretty good, but most of my memories of it are of sitting in Dallas traffic going to or coming from the conference venue. Fortunately, traffic was not an issue this time and I got to spend much more time attending the conference itself.

Relatively speaking, however, I don't think I enjoyed the 2011 ISDC quite as much as the 2007 ISDC. I found myself watching speakers and panels drone on and on about space policy and politics, with the occasional historical perspective on NASA and the space industry. After a couple of days of this, I found myself to be underwhelmed and mostly bored with the presentations in the main conference tracks.

Well, as it turns out, they were keeping most of the best speakers and presentations sequestered in the lunch and dinner talks - each of which required a $30 or $50 meal ticket to attend. Since I was attending the conference on my own dime, and since I have spent much of my adult life so far as a poor grad student, I couldn't bring myself to shell out an extra $200-$300 on top of what I had already committed to travel, hotel, and registration. Fortunately, the NSS has started to post these talks online. The Moon and Back blog has also been posting presentations and interviews from the conference.

Some Observations

The theme of the conference this year was "From the Ground Up." Supposedly, this was to be a conference about what it takes to get us from here to there - there being a significant amount of human activity in outer-space. What that amounts to, apparently, is much haggling and debate about our national space policy, FAA regulations, NASA's human spaceflight budget and Congressional mandates to build a super-heavy-lift launch vehicle.

As an engineer and a scientists, I went into the ISDC hoping that I would hear some discussions about the technological and engineering challenges that need to be addressed before humanity can begin to leave Earth in large numbers and for long durations. However, as the conference wore on, I began to see that the technology is no longer the long pole in the tent. Engineering problems have engineering solutions, and with proper resources allocated, an engineering solution can be found to all of the problems currently facing extended human spaceflight. What we are lacking are those resources, and a coherent strategy to guide the development of the required technologies and infrastructure.

Despite my overall disappointment with the conference, there were a few high points as well. There was an excellent presentation by Michael Doornbos of Evadot. I think I will have to dedicate an entire blog post to that one. Then there was also the Google Lunar X-Prize panel, also moderated by Michael. And then I got to meet with a couple of fellow Part-Time Scientists team mates. We worked together to hack one of our R0 rover prototypes into working order in time to demonstrate it during and after the GLXP panel session.

Michael has a passion for space and a wonderful ability to pass it on to just about anyone he meets. His talk was on "How to inspire kids by thinking big in space." His concern is that we are not doing the kinds of things we need to be doing in order to give our children something larger to aspire to. Long gone are the days when everyone knew the names of the astronauts and felt intimately connected to their missions.


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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