Plasma Wind

small turbojets: the turbomachinery

Here's a look at the turbomachinery:

The compressor is a single-stage, radial compressor possessing 5 blades, and 5 splitters.  It's got about an 8 deg. forward lean, and about 15 deg. of sweepback.  I don't have direct measurements of its delivered pressure ratio, but my power balance calcs. suggest it should be around 3.8.  At a air flowrate of 0.58 lbm/sec, and an efficiency of 82%, the compressor would absorb around 70 hp at full power.

Small Turbojets

Here's some pictures of a small turbojet that I use as an experimental testbed.  By using a small, low cost turbojet (this one cost me less than $1200, including all hardware, electric starter, FADEC, fuel pump, and batteries), I can run many tests very quickly and for very low costs.  I can also try out different, advanced technologies that are too risky and/or too expensive with a bigger machine.
This is an example of using many trial-and-error tests to development technology, as discussed in a previous post. 
Here's a look "under the hood": This turbojet makes about 12 lbf thrust at full power.  It consumes about 0.007 lbm/sec at full power, resulting in a TSFC of around 2.19 lbm/hr-lbf.  The turbojet masses about 1.87 lbm, yielding a thrust-to-weight of about 6.42.  At full power, the nominal rpm is approximately 160,000 rpm.
(if you're interested in other specs, please let me know via comments).

For the Love of Technology

We love technology (from the Greek, literally “know-how”). It’s so…so… American.  We’re a culture evolved from all the do-it-yourselfers, early adopters, pioneers, independent thinkers that left Europe a few centuries back, so its only natural that we want to know how to do something better, easier, or maybe so that we can make a buck, or maybe just because we like knowing how to do something that other people can’t.  This is something we seek out and embrace.

 But the implementation of new technology is a different story.  New technology faces the challenge of displacing the incumbent technology.  When people are faced with this decision, they make a reasonable assessment: does the new technology and its claimed benefits outweigh the difficulty and risk of replacing the old technology, especially when the incumbent way is working, making money, is can be counted on?  (Way) More often than not, the incumbent wins, and the new technology is not implemented. The difficulty of implementing new technology and innovations is well-documented and analyzed in Clayton M. Christensen’s books, The Innovator’s Dilemma, and The Innovator’s Solution.  Christensen basically shows that new technology has to enter “from the bottom up”, by providing innovation for the needs of customers that aren’t being served by the incumbent. 

 Recently, considerable discussion has arisen from John McGowan’s article in the Space Review regarding technological innovations that might make cheap access to space possible.  I think the significant contribution of McGowan’s article is the reiteration of the fact that technological development requires many trial-and-error attempts in order to work out all the kinks. 

 I provided some comments to the article, in an attempt to shed some light on specific approaches to technical innovations for low cost space access.  In my opinion, there is almost no better reference to this issue than John London’s seminal book, LEO on the Cheap, which can be downloaded here.  London points out that simplicity and design choices can radically alter development and operational costs, and that there are cultural issues involved as well. He provides excellent examples as well as recommendations.  Col. London (ret) is a rather amazing person, and is one of the few people I know to have served in the Air Force (as an officer), and in NASA and the DoD (as a civilian), and has remained a tireless supported of the "New Space" Industry.  Not too long ago this was considered fringe territory, and it was John who coined the term the "radical rocket underground".  So he's not just talking out of his hat, he's been there, done that.

 LEO on the Cheap essentially provides a roadmap on how to develop low cost space launch systems.  And in fact, many of his recommendations and observations have found their implementation in some of the current space launch systems, such as SpaceX, Armadillo Aerospace, XCOR, and others.

 Finally, I think its worth noting, as I did in my comments to McGowan, that we may eventually rediscover the advantages provided by spaceplane-type launch vehicles which take off from a runway, fly an envelope-expansion type flight, and then return to land. Despite their larger dry mass fractions, aircraft-type flight operations allow incremental flight testing, and hence, many more trials for a given development budget.

 But the question remains as to why this has taken so long.  This is not a simple question to answer, because there have been, in my opinion, quite a number of contributing factors.  But, my best attempt at putting it in a sentence or two goes something like this:  the Space launch industry emerged largely as the product of post-World War II industrial practices and the success of large, government-led projects.  Subsequently, the aviation and aerospace industries were largely usurped by cold war imperatives.

 Further discussion and explanation of what I mean above will require additional posts, which I’ll provide later.  But the upshot of this, at least for Americans, is that launch vehicle design, development, and the selling of launch services got wrapped up with only one customer, the U.S. Government.  The U.S. Government became the incumbent, and it’s taken a long time to create and find markets for these alternative launch services.

 I have to remind myself that new markets have to be created.  They are created when there is an exchange of things between someone who wants and/or needs something, and someone who has something to offer.  Usually, when someone wants something that doesn’t currently exist, creative people scramble around to provide that something.  However, if a creative person has something that they are offering, and no one wants it at the moment, then it sometimes takes a while to find someone who does want it, and sees its value.  Oftentimes, people don’t even know what they want except more/better/faster/cheaper of what they currently have. 

 How does this apply to our current launch markets?  We have people who need launch services, and we have people who provide those launch services.  The people who need launch services want more/better/faster/cheaper launch services than they have now.  Incumbents, like Boeing, LockMart, Orbital, have the advantage.  This is the innovator’s dilemma.  New launch providers, SpaceX, Blue Origin, TGV Rockets, et al, are seeking ways to “enter from the bottom up” by providing lower cost services to customers who aren’t being served by the incumbents.  This is the Innovator’s Solution.  And I think it’s going to be successful beyond our wildest reckonings.

Propulsion Technology Development for Low Cost Space Access

John McGowan has an interesting article in The Space Review regarding ways to develop low cost space access via improvements to propulsion and power technology.  The article can be found here.  This is my cup o' tea.

Basically, if you can do many trial and error testing, then you have a much better chance of creating better technology.  To do many trials, you need to make sure that each trial doesn't cost very much.  Then you can do more trials for a given amount of funding. 

This is why I built my own Air Turbo Rocket (ATR), so that I could do multiple, low-cost test runs for engine development. (here is my  ATR). 

The Evolution of Acceptance

Technology, ideas, social customs, and other related things, often are not immediately accepted.  In fact, they are as often as not rejected initially.  However, as they stay around long enough, their acceptability changes, ripens.  There is an evolution of acceptance.  This evolution of acceptance has been articulated previously, as a sort of saying, or set of quoted phrases, composed of several stages. I’ll expand on it with the addition of an additional and final stage, which has some truth, but mainly because it’s just funny.  Here is, then, the Evolution of Acceptance:

 1.  “That’s Impossible”

 2.  “That may be possible, but it’s Impractical”

 3.  “I said it would work all along”

 4.  “That was my idea”

 If you look up the history of ideas, concepts, technologies, you can often map these stages onto their evolution.  I give you, for example, the personal computer:

1. Impossible:  “Computers require a room sized space.”

2. Impractical:  “The worldwide need for computers might be around five or six”

3. Obviously Practical:  “the IBM PC”

4. My idea:  “Windows”

One can also map these stages onto current technology, that hasn’t progressed yet through all the stages.  My example, personal spaceflight:

1.  Impossible:  “It takes an entire nation to create a suborbital flight vehicle”

2.  Impractical:  “Ok, so the Spaceshipone worked, but who cares about suborbital flight”

That’s where we are right now, on stage two.  Soon, we will progress to stage 3, and then onto stage four.  Here’s what they will look like:

3.  Obviously Practical:  “I’ve been working for years on suborbital spacecraft.  Why, we had a design for one back in 1965 that we designed with slide rules and ham sandwiches”

4.  My Idea:  “I am generally credited for having created the suborbital flight market”

The difficulty level is inversely proportional to the stage number:  the first stage is harder than the second stage, etc.  

Often when starting on a new idea, concept, project, the weight of evidence is against you.  Conventional wisdom and experience have been wrung from what has gone before, and, if it’s worth much of anything, has been hard won.  So starting new requires something more.  It requires belief and vision; it requires a superlogical rationale for continuing.  And by superlogical rationale, I don’t mean extremely, extremely logical, I mean a rationale that transcends logic; a rationale that is consistent, but relies upon propositions which may be true, but cannot be proven within the given system of knowledge. 

I encourage each and every one of you who read this, to embrace your superlogical rationales for doing what you do, even when you are the only one convinced by your arguments (maybe your arguments don’t even convince you).  This is how advancements are made, large and small.  Since this post opened with an old saw, I’ll close with one:

"those that say it cannot be done should not interfere with those who are doing it"

The Perishability of Technology

One aspect of technology that particularly fascinates me, is the process of technological degeneration, i.e. how technology gained can in fact be lost. We tend to think that the world we inhabit now represents the acme of technological progress, and in most of the ways that matter, this is true.  Our current technological prowess has emerged after thousands of years of more or less continuous progress, one discovery leading to another, several advances combining together to foster one great leap forward, or a new discovery.  James Burke’s famous television documentary Connections provided many fascinating accounts of this technological advancement. 

 Yet this steady, upwards-moving progress is not necessarily a given.  Furthermore, advancements made are quite perishable.  Consider, for example, that of the Roman Empire.  At the peak of this great civilization, numerous important technological advancements had been made in civil engineering, including structures (the barrel arch), materials (concrete), and hydraulics (aqueducts, siphons, valves), as well as the important advancement of how to organize and execute large projects: the technology of project engineering.  However, as the empire fragmented and eventually dissolved, so too went their technological capabilities.  Following the collapse of the Roman Empire, building technologies in Western Europe would not equal what the Romans achieved for nearly 1400 years (say 400 A.D. to the 18^th century).  I recently read where a large Roman bronze valve, used for water flow control, was finally taken out of service, having performed satisfactorily for over 1500 years. 

 Other civilizations have also had highly developed technological advancements that would not be equaled for millennia.  The ancient Egyptians had a technological civilization that was so advanced, that it is still a wonderment to this very day, as it was to Medieval Europeans, the Romans, the Greeks, and the Persians.  The great pyramid at Giza was the tallest man-made structure in the world until it was finally surpassed by the Eiffel Tower ; build for the Exposition Universelle of 1889. 

 Yet these civilizations, and many others (Mohenjo-daro, Tiahuanaco, Ba’albek), grew, reached their zenith, declined, and eventually disintegrated, usually leaving behind remnants of their past greatness.  The reasons for their declines are multifaceted, and not always clearly understood.  But my question is, what happens to the technology as your civilization declines?  Do you know someone that used to know how to do some process, but they’re no longer alive?  Perhaps you remember when things actually worked, but they don’t any more.  Do you just settle for less, and tell your children about the good ‘ol days when we used to have running water and telephones? 

 The idea of the perishability of technology I find very interesting, and somewhat disturbing, because it suggests that our continuous progress is by no means inevitable.  Sure, you’ll have a world war now and again, but the important technological civilizations survived, rebuilt, and in fact, net technological progress was often made.  But what about some other global catastrophe?  Or perhaps there could be some sort of gradual disintegration of civilization, like what happened to the Roman Empire, causing us to sink back into a more primitive and less technologically-capable condition.

 I often see movies and dramas about what happens in the aftermath of some great catastrophe or societal collapse (The Road Warrior, From Here to Eternity, Waterworld, The Postman, etc., there’s quite a list), and you see people trying to cope with what’s left of their civilization.  What you don’t see (because it’s hard to depict and perhaps not particularly dramatic) is people making the choice between slumping back into using less technology, or trying to maintain and improve what ever technology is left.  This process is composed of thousands of smaller choices that you make every day, throughout the day. “I’m going to go to my job today”, “I’m going to read a book on how to do something today”, “what can I create that’s new to me today?”, etc. 

 It seems that most of us would make the choice to keep trying to move forward, to maintain and improve existing technologies because we prefer them.  This approach to living is well articulated in Kevin Kelly's recent column “The World without Technology”:

http://www.kk.org/thetechnium/archives/2009/03/the_world_witho.php

So even if we had a major breakdown in our civilization, for any number of reasons, there might still be enough people around to recover, and preserve whatever technological gains we had made.

 And yet, we know from the historical record that these massive failures of civilization do occur (as previously discussed above), and that they can take thousands of years to recover from.  Perhaps some technology is lost for good (ref 1, 2).  Why does this happen?  Maybe that’s the question I’m asking. 

 These questions have direct bearing on the issue of humankind's expansion off the planet.  I will be exploring these questions and the general issue of off-planet expansion as part of my regular postings.  By giving consideration to the processes of how technology can be lost, in addition to how it is gained, perhaps that will provide some insight into our motivations for continuing to know more, to understand better, and to move forward and outward.

 References

1.  The Technology of the Gods; D.H. Childress; ISBN 0-932813-73-9

2.  Ancient Man:  A Handbook of Puzzling Artifacts; W.R. Corliss; ISBN 0-915554-03-8

Unit Conversion Tool

In my day-to-day bustle of analysis, modeling, and calculations, I find I have an almost continuous need to do unit conversions:  inches to meters, liters, to gallons, Fahrenheit to Kelvin. 

Especially onerous are the unit conversions required for heat transfer calculations.  Often data sources are given in one set of units and/or system, and you need them in another.  Specific heats, thermal conductivities, and convection, viscosities, require care to get the units correctly converted.

Attached is a simple spreadsheet unit converter that I use myself.  My convention is that the numbers you need to input are blue, and calculated values are black.  One can go english-to-metric or metric-to-english via the appropriate worksheet.

Currently, I only have length, density, pressure, temp, and mass.  As time goes on however, and if it seems people are finding this conversion utility useful, I will add addition unit conversions, esp. the heat transfer conversions mentioned above.

Until then, I hope you'll give this converter a try, and provide feedback as to its utility.  I must mention that no warranty is expressed or implied as the the correctness of these conversions.  I do my best to make sure they are correct (I use them myself), but you, the user, are the party responsible for the correctness of your calculations.  So if you download this spreadsheet, it becomes yours as to the values you create with it.

Happy converting.Download Unit converter 05-01-09