Category Archives: Astronomy and Aerospace

The latest hiss from Jupiter

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The 20.1 MHz radio receiver kit we ordered from Radio Jove arrived last week.  Lots of tiny components to solder onto the PC board.  I seem to have forgotten the color code for resistors. 

The kit comes with conductors and fittings for a dual dipole antenna. I’ll have to go to Home Depot and buy parts for the support structure.  The antenna is going to take a bit of real estate to set up.  Given that Jupiter is low in the sky for a few years, it is desirable to contrive a means for narrowing the antenna beam to help with some noise rejection.  A properly configured dual dipole 15 or 20 ft off the ground helps a bit. 

A powerful station already broadcasts at 20 MHz (WWV), out of Ft. Collins, CO, so the receiver is offset at 20.1 MHz.  Jupiters cyclotron radio emissions are strongest between 18 and 24 MHz.  For locations distant from Ft. Collins, the broadcast at 20 MHz may be irrelevent. The ionosphere is mostly transparent to 20 MHz radiation on the night side of the earth, so transmissions from interfering sources in this band tend to propagate into space at night rather than reflect off the ionosphere and go beyond the horizon.

Th’ Gaussling has been busy studying the basics of antenna theory.  It’s quite interesting, really.  An antenna is basically a transducer, converting energy from one form into another.  The knowledge of antennae is something of a dark art.  I have had to scrounge to find resources that explain without too much forgotten calculus. 

Once you have antennae on your brain, you begin to notice them everywhere. All sorts of them. Yagi’s, dipoles, dishes, mast antennas, and folded dipoles jutting off of every imaginable high spot. I have one bolted to my house. 

The side benefit for yours truly is that it has forced me to have a hard rethink about electromagnetic radiation and the mechanism for its generation. We organikkers generally don’t spend a lot of time thinking about radiation emission and propagation. 

There could be some pedagogical advantages to introducing students to electromagnetic radiation in the radio spectrum rather than the visible range. The acceleration of charges in an antenna element and the subsequent perturbation in the charge field around the charged particle seems to be conceptually easier to reach than the usual abstractions showing the 3-D rendering of a sinusoidal wave in most textbooks. In fact, I have never seen a good representation of visible photon emission beyond arrow pushing on an energy diagram.   Who knows, maybe a student would learn something about electricity as well?

Hey. Check out the Quantum Slacks by Haggar.  The first of their Non-Newtonian line.

Ullage Motors

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If the reader is interested in the history of aerospace or rocketry, I’d like to recommend the book Saturn, by Alan Lawrie and Robert Godwin, Apogee Books, 2005 (ISBN 1-894959-19-4).  Lawrie is the author and Godwin produced the DVD that is included. The book is a comprehensive history of the Saturn V launch vehicle. 

Flipping through the book I happened to land on page 59 and a section on Ullage Motors.  If you have ever handled bulk liquids in drums or tankers, you know that there must be a certain fraction of the tank capacity left unfilled with liquid.  This gas space, or ullage, prevents rupture of the vessel by expansion of the liquid contents.

Ullage motors were used to get around certain problems associated with using liquid phase propellants in weightless conditions. The contents of a liquid propellant tank always include a volume of ullage.  In free fall it is possible for void spaces to form near the propellant transfer lines. 

Saturn V ullage motors were ammonium perchlorate solid rocket motors externally mounted on the lower part of the second stage.  Immediately after first stage engine cutoff, the first stage would separate and for a short time the upper stages would be in free fall.  To prevent transient fuel starvation problems during engine start it was desirable to force propellant to the bottom of the fuel tank prior to the engine start.  To accomplish this, a group of small solid rockets were fired to provide a bit of acceleration to force the liquid propellant to the bottom part of the tank. The eight ullage motors burned for 4 seconds and each generated a reported 22,500 lbs of thrust. 

Curiously enough, there are a reported 46 intact ullage motors in earth orbit.  The authors conclude that these remnants of the Proton 4 rocket represent explosion hazards. 

To the Moon!

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It is hard for most of us to tell but the US is in the early phases of a moon project.  It has adopted the same configuration of command module and lander as the Apollo program.  NASA intends to make a few exploratory missions lasting a week or so and then develop the capability for 180 day missions to the moon. This lunar “base” project is really a local rehearsal for a more ambitious manned Mars landing.  It is called the Constellation Mission. 

NASA has announced the development of two rockets for this mission- the Ares I and the Ares V.  The Ares I uses an in-line single solid rocket booster (SRB) for the first stage and a liquid propellant second stage to boost a 55,000 pound payload into low earth orbit.  Ares I is equipped with a emergency escape rocket in a tractor configuration analogous to Apollo.  As stated in the website, Ares I will be used to put the crew module in orbit for rendezvous with the ISS or cargo modules. 

The Ares V uses two SRB motors strapped to a liquid first stage engine in a fashion similar to the space shuttle. But the crew module will not be on this system.  Ares V is a cargo lifter and will carry 286,000 lbs of mass into low earth orbit.

NASA will be retiring the space shuttle system in a few years. The next man-lifter will be Ares I.  Evidently their faith in the SRB system is high.

That sucking sound heard around NASA these days is the sound of money being pulled from all over the agency and being dumped into this program. We’re going back to the moon, but with no real increase in funding.  Program managers are nervous. 

Friday Link-o-Rama

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The Russian cruise missile submarine Kursk went down in the Barents Sea, killing all aboard.  The first link has interesting pictures of the remains of the sub after it had been recovered. The second has interesting background information.

Need a spectrograph for your backyard telescope?  Check out this cool instrument from SBIG.  The good folks at Brookhaven have a table of nuclides online as well as a “Nuclear Wallet Card“. Golly, maybe one day we’ll have electricity too cheap to meter…

Check out the Deep Space Exploration Society- DSES.  They have resurrected a pair of dishes for the purpose of amateur radio astronomy.  They have been doing a sky survey at 1420 MHz.

Looking for something more refractory than the head of Karl Rove?  Check out FiberFrax.

A380 Evacuation Test

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Here is a link showing the evacuation of an A380. This airplane disgorged 873 people in 77 seconds.   So I’m thinking, what if you don’t have a planeload of orderly Germans who know how to get moving? What if you had a load of fat, jetlagged American touristas with expensive stuff in the overhead storage? You’d never get out of that airplane alive because some nimrod would have to get up and grab something out of the inside of a zipped bag, dooming everyone to incineration.

When one of these meat wagons eventually goes down, it is going to be like a small town got wiped out.  Like a screaming village falling out of the sky.  In a water landing, this thing is going to cartwheel like a drunken gymnast when a wing dips and grabs the water, and from the parts of the fuselage that shredded open will fly whole rows of horrified passengers, some still gripping their bags of pretzels.  The cabin sections will come to a halt and sink like a stone. 

Oh.  Well, I guess most of them do that.  Regardless, it ain’t gonna be pretty.

Here is a test of the braking system of the A380.  Ever wonder what happens when a big turbofan throws a blade?  The folks at Rolls Royce released this video of a test.  P&W released one as well.  This is what you try to avoid when working around jet engines.

Boron Cosmochemistry

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Next time you wash your laundry with borax, pause for a moment and consider the path those boron atoms took to get to your dirty shirts.  The Big Bang started the universe with H, He, and maybe a bit of Li.  The rest of the periodic table had to be produced by nuclear reactions within the core of a star or during the explosion of a star.  This occurs through either the fusion of charged nuclear particles (nuclei included) or absorbed neutrons to nuclei, perhaps followed by a decay cascade.  Note to reader: astronomers are in the habit of referring to elements heavier than helium as a “metal”. 

In the core of a star there exists a complex kinetic circus of multiple simultaneus synthetic channels involving both atomic weight buildup and disintegration.  Nuclei less sensitive to the reaction conditions may accumulate and delicate nuclei like boron have but a fleeting existance and are consumed.  In addition to stability to the reaction conditions, particular combinations of protons and neutrons tend to be more stable and accumulate if only by the lack of propensity to decay. 

While the elements C, N, and O are cosmically quite abundant, at least in comparison to the rest of the elements (3 to 92), the elements Li, Be, and B (LiBeB) are relatively scarce. 

Because boron was too heavy for Big Bang nucleosynthesis and too reactive to accumulate in a stellar core, it’s cosmic abundance is low.  What little that is found did not arise as simple boron ejecta mechanically boosted into the interstellar medium by an explosion or as entrained mass from stellar wind.  It was formed from more abundant elements like CNO that had already been ejected- elements that would be subjected to a barrage of highly energetic particles.

LiBeB are thought to be “spallation” products from interstellar CNO collisions with cosmic rays.  From the linked chart, we can see that C, N, and O are relatively abundant.  So over a multibillion year timeframe of stellar evolution, early massive stars can live and die, dispersing metals into nearby space.  Accumulated heavy elements can then be exposed to cosmic ray fragmentation.  The source of the cosmic ray particles in these collisions is somewhat up in the air.  Some of the latest thinking suggests that these energetic cosmic rays yielding spallation products are from especially energetic sources like Wolf-Rayet stars or type II supernova events.  There is an indication that boron can come from two spallation channels- cosmic ray and neutrino-induced spallation of carbon. 

So, the picture thus far- boron arises from the energetic collision of particles outside of a star.  Heavier nuclei will fragment under cosmic ray bombardment and some combination of B-11 and B-10 are formed.  What is interesting is that this is a dispersive phenomenon.  By contrast, on earth, boron is found in deposits as the hydrate of the alkali metal salt of the oxide- Borax.  There are a variety of distinct mineral compositions that contain boron.  On earth, a bit of the dispersed boron was somehow concentrated into ore bodies.  This is where geology kicks in.

Hydrothermal action near subduction zones can dissolve borates in hot, pressurized water and deposit them at the surface where the solid borates come out of solution on cooling.  This process evidently partitions the isotopes of Boron slightly.  Over time the process continues until geological events interrupt the deposition process.  If the solubility of the borates is relatively low at surface temperatures and pressures, then weathering will not further disperse them into the hydrological cycle.  Thus they form a deposit.  Layers of sediment accumulate over the borax deposit and eventually geological processes move the layer underground. Eventually, uplifting, weathering, and mining makes the deposit accessible.  Through the miracle of marketing, distribution, and 18-wheeler trucks, this spallation product can be used to clean that unsightly mustard stain from your shirt.

News Flash! Most energetic supernova ever observed was detected in the galaxy NGC-1260 by Chandra.

“Riding Rockets”- A Review

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I just finished reading Mike Mullane’s autobiographic “Riding Rockets“.  Mullane is a retired mission specialist astronaut with 3 missions under his belt.  It turns out that Mullane and I share one discouraging life experience.  I also wanted to be an astronaut and was also disappointed to learn in college (Air Force ROTC) that my nearsightedness would prevent me from getting a pilot slot in the Air Force or Navy.  Undaunted, Mullane went on to the next best option of GIB (Guy In Back) and became a USAF weapon systems officer.  His transition to astronaut from GIB was made possible by the NASA’s decision to eliminate the requirement of pilot experience as a prerequisite for mission specialist .  No doubt his degree from West Point, 150 combat missions in Viet Nam, test pilot school at Edwards, and a masters in aeronautical engineering helped him a bit.  I realized that I was a nearsighted, pathological smartass and left ROTC and went into chemistry.  Mullane persisted and got into space. I succumbed to the enchantment of organic chemistry and explored conformational space.

Mullane writes rather well and provides a reasonably balanced narrative over the time spanning his career. I would say that the main reason to read the book would be to get some insight into life in the astronaut corps.   If you put two people in a room, you have politics.  And it is no different with astronauts. Mullane details what can only be described as a byzantine system of decision-making for mission assignments and the characters who made these decisions.

Mullane describes in considerable detail the experience of a scrubbed launch. He bid farewell to his family and strapped a fully fueled shuttle to his backside 9 times for 3 launches.  Mullane tells of his own private fears and the fear that was (is) felt among many other astronauts- a feeling quite apart from the confident and laconic persona they might show in public. Indeed, he has been outspoken in regard to the safety of the shuttle fleet and in a manner uncharacteristic of astronauts, generally.

Far from being a monolithic group of superheros, the astronaut corp consists of a surprisingly diverse group of individuals.  As a group, astronauts are super achievers and not lacking the usual spectrum of attributes you might expect.  There is no shortage of ego or swaggering bravado.   Historically, astronauts come from an aeronautical background and as such, are accustomed to the flight environment and the norms that go along with it. During Mullanes tenure at NASA, the program saw civilian and other non-traditional astronauts take increasingly important roles in the mission.  In particular, this period of time following the first trial flights saw female astronauts accumulating a considerable number flight hours on orbit.

He describes in detail how the astronauts felt after the loss of Challenger and Columbia.  Mullane is of the opinion that the shuttle should have a better crew escape system.  Evidently he logged an ejection from an F-111, so he has first hand experience with bailout systems. There are literally thousands of parts and systems whose failure could tragically end a mission and the lives of its crew.  But like everyone who wants to fly in space, you swallow your fears and strap in anyway.

In the context of books in this genre, I’d give him a A- for his courage to be critical of NASA.  He now works as a motivational speaker.

Plasma Songs From Space

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The radio telescope project has begun. Today I ordered a 20 MHz receiver from Radio Jove.  While we wait for that to arrive we have to source an 8 channel Analog to Digital Converter (ADC) for the data feed into RadioSky-Pipe.  RadioSky has run out of ADC’s, but they recommend Kitsrus out of Hawii.  

We have three surplus computers I bought from work.  Have to pick one and get an operating system (Windows 2000, probably, though Linux is a possibility), a monitor, and a keyboard. 

The biggest issue is the recommended dipole antenna. The kit specifies an East/West 23′ 3″ ft dipole with a 32 ft footprint, is ca 10 ft high, and uses guy wires to stabilize it. Sounds like a trip hazard and a target for vandalism to me.  In that vein, I have been looking at alternative antenna configurations. The folks at Radio Jove are reticent to recommend one, presumably because it is a step away from simplicity for classroom use.  That’s fine. I’m an experimentalist.

One problem with moving away from the dipole antenna design is the unwieldy half-wavelength dimensions. While the dipole eats up real estate, it is structurally simple.  One interesting design is the Moxon antenna.  This antenna uses a bent driven element with a bent reflector element.  Most people use it with the elements in the horizontal plane, thus picking up horizontally polarized signals.  While this makes sense for communications, I’m guessing that the 20 MHz signals from the sun and Jupiter are probably not significantly polarized.  

The Moxon is significantly more directional than a dipole with a front to back ratio 15 to 20 db.  This means that it must be pointed at the radio source for maximum gain.  But its directionality also confers some rejection of terrestrial signals from other directions. From what I can tell, the gain from this design with its reflector element is on the order of 5 db.  This is higher than a dipole but lower than a multi-element Yagi.

We’ll get some baseline experience with the recommended antenna and then begin to look at other configurations.

In my view, one can never know too much about electronics.  This site has some interesting circuit animations.  Cheers!

Encounter with Asteroid 2006 VV2

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An asteroid said to be approximately 1 mile in diameter will have a near encounter with the Earth at 11 pm Pacific Daylight time today, Saturday, 31 March.  The rock will pass within 3,900,000 kilometers of our planet.  The asteroid is passing south against the backdrop of the constellation Leo this very moment.  It is predicted to be 10th magnitude and will require a 6 inch telescope or greater to see. Its proximity to a nearly full moon will not help the seeing. This NASA JPL link will allow you to generate an ephemeris.  Spaceweather.com has a stereogram of the object passing the galaxy M81.

For tickets to this momentous event, send $20 cash to Gaussling.google.internet. Operators are standing by.

Yves Rossy and his flying wing

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So, there is this Swiss fellow named Ives Rossy who has developed a strap-on wing assembly complete with a small turbine engine.  His flight profile goes like this- He launches from a high wing single engine aircraft (a Pilatus) at altitude.  As he drops, he deploys the folded wingtips and achieves a stable glide. I can’t tell from the video, but I suspect that he starts his engine prior to leaving the plane.  Once he has his glide established he throttles up the engine and begins powered flight.  Clearly he is maintaining level powered flight and even appears to climb.  This is no mere glider. He ends his flight at altitude near the intended touchdown point and deploys a paraglider-type chute and lands by parachute. 

This is nothing short of amazing.  There are other video’s showing different flights and a few details of the wing.  As flying folk know, when you go aviatin’ you are actually flying the wing. Passengers may focus on the fuselage, but the pilot is busy up front making sure the airstream is moving over the wing properly. However, the fuselage is not just a cargo space or place to sit and leer at the stewtrons while munching pretzels.  Significantly, it connects the empannage, or tail assembly to the wing. 

The job of the empannage is to hold the vertical and horizontal stabilizers in place.  The horizontal stabilizer and its articulated control surface called the “elevator” is a concession to an unfortunate aspect of wing behavior.  A “normal” wing (i.e., a Clark Y) is just an oddly shaped truss built to develop a pressure imbalance in an airstream.  This imbalance gives rise to lift which counteracts the force of gravity.  But a normal cross section wing will also develop a pitching moment, or the tendency for the trailing edge to pitch upwards and the leading edge pitches downwards about the center of lift.  The job of the horizontal stabilizer downstream of the wing is to counteract this downward pitching moment. 

One of the critical design features of the flying wing was to counteract this downward pitching behavior.  One way to do it is to shape the trailing edge of the wing upwards to cause the airflow to impart some counteracting downward force on the downstream side of the wing.  So, if you look at the details of Rossy’s wing, you’ll see this upward curving lip on the trailing edge.  He is a clever boy.

My hat is off to this guy. Yves, my next glass of Fat Tire is in your honor!