Tuesday, January 13, 2009

Heinlein called the "Moon a Harse Mistress". Bova has explored Mars environment. Mars is not like Earth for this Mission; Moon was just a small step.

Earth and its unique life-support characteristics

One such piece of evidence arose recently from an astronomical mission to Mars. A sensitive magnetometer on board the Mars Global Surveyor reported some unexpected results.1 It found that Mars’s magnetic field is, at best, forty thousand times weaker than Earth’s, ten (or more) times lower than the limits established by previous Mars studies.2 With such a weak, or possibly non-existent, magnetic field, the Martian surface has virtually no protection from deadly solar x-rays.
The Global Surveyor magnetometer also found a few “magnetic anomalies” on the Martian surface, rocks containing “relic” magnetic fields.3 The magnetic characteristics of these rocks suggest that Mars has no internal dynamo now but that such a dynamo probably existed long ago when Mars was young. This electromagnetic and geological history represents a solvable puzzle.
Twenty researchers concurred in the solution. Their published reports show that the magnetometer’s findings make sense if Mars’s core contains a relatively small percentage of sulfur. If a planet’s core contains more than 15% sulfur (by mass), a solid inner core can never form. If the quantity (by mass) of sulfur in the core is considerably less than 15%, a solid inner core can form; however it will grow so rapidly that it soon engulfs and freezes out the liquid layers between it and the planet’s mantle and crust. Without a circulating magnetic fluid between the planet’s solid core and mantle, a strong magnetic field will never develop. Without a magnetic field, the planet has no shield to guard it from the sun’s x-ray radiation.
This discovery about Mars’s lack of such shielding certainly impacts any plans for a manned mission to Mars. The dangers, already known to be grave, now seem graver by far. At the same time, this new understanding about the intricacies of magnetic field formation reveals another wonder of Earth.
Life can exist on Earth because Earth has a strong, stable magnetic field. This field’s strength and stability are determined, in part, by the abundance of sulfur in Earth’s core. Remarkably, this abundance is “just right” for life, as are all the other characteristics that go into formation of a life-protective, magnetic-field-producing dynamo, one that shields life not just for a short time but for a few billion years.

M. H. Acuna, et al, “Magnetic Field and Plasma Observations at Mars: Initial Results of the Mars Global Surveyor Mission,” Science, 279 (1998), pp. 1676-1680.

OK. What do we have our Chemistry and Biology Students working on for this Mission? Energy Sources?

Light-powered bacterial enzyme that releases hydrogen from water could lead the way to new strategies for generating the energy-rich gas.
The lack of low-cost ways to create hydrogen gas is one of the main barriers to the dream of economies fuelled by hydrogen not oil. A class of enzymes called hydrogenases are used by organisms to convert hydrogen ions to hydrogen gas during anaerobic - without oxygen - respiration. These enzymes have long interested chemists searching for alternatives to existing, expensive, platinum-catalysed hydrogen generation.
Hydrogenase Problem
The metal-containing enzymes are all crippled in varying degrees by the presence of oxygen and are also damaged by the very hydrogen they produce. That makes them difficult and expensive to use on industrial scales, says chemist Erwin Reisner, at Oxford University in the UK.
Bacterial gift
Now Reisner and colleague Fraser Armstrong have shown that a newly discovered bacterial hydrogenase is much more resistant to both gases.
The nickel, iron and selenium-rich enzyme, first isolated by Juan Fontecilla-Camps at the University of Joseph Fourier in Grenoble, France, is produced by a sulphate-reducing bacterium.
Its efficiency is unaffected by the presence of hydrogen gas, and it continues to work even if the surrounding air contains 1% oxygen by volume - ordinarily even a few parts per million of oxygen would block hydrogenase activity.
The new enzyme also binds strongly to titanium dioxide nanoparticles, making it easy to produce a kind of light-powered, hydrogen-generating dust.
'Promising trial'
The dust particles are each attached both to the enzyme and to light-absorbing dye molecules that are used in some solar cells.
In the presence of an electron-donating buffer solution, the dye absorbs light and releases excited electrons, which then pass to the enzyme. Suitably energised, the hydrogenase then converts hydrogen ions from water molecules into hydrogen gas - just as they would during the bacteria's respiration.
After a small sample of the nanoparticles spent 8 hours in a buffer solution under a tungsten-halogen lamp, the headspace gas above the solution was 4.6% hydrogen by volume - a result Armstrong calls "promising for a first trial". In a control experiment without the enzyme only trace quantities of hydrogen were present.
The reaction falls short of "true water splitting", says Armstrong. This would require another enzyme to release oxygen gas from the water molecules and provide the electrons to fuel the dye, making the buffer solution redundant. Developing that complete system is Reisner and Armstrong's next goal, they say.
Catalyst inspiration
With the current set-up, the reaction rate is comparable to that achieved using platinum catalysts in place of the enzyme, so studying the new hydrogenase might inform the "design" of simpler catalysts that are as effective as platinum, but considerably cheaper.
Marc Fontecave at the Atomic Energy Commission in Grenoble, France, is working on such catalytic molecules. "What we need is catalysts working under aerobic conditions and not just 1% oxygen," he says. "Obviously, I'm more confident at the present stage in this type of catalyst than in hydrogenases."
Chris Pickett at the University of East Anglia in the UK agrees, but is still impressed with what has been achieved with the natural hydrogenase. "It is the enzyme systems which are showing what can be done and which are currently making the pace," he says.
Journal reference: Chemical Communications (DOI: 10.1039/b817371k)
sulphate-reducing bacterium (archaebacteria) To be a member of this club you need:
To be able to metabolize sulphur compounds.
To be a prokaryote.
To be anaerobic (killed by oxygen) and maybe aerobic.
To be photosynthetic or non-photosynthetic.
To be autotrophic (use carbon dioxide as food) or heterotrophic (use organic matter for food).

Wednesday, January 7, 2009

These things have a way of working themselves out...


Rockets Construction Instructions with Videos

Rockets are one of the most amazing technologies humans have invented so far. We use them for space travel, wars, and for fun! Just some of the fun things you can do with rockets are to make model rockets, fireworks, and tiny rockets made with matches! But not all rockets require a dangerous combustible propellant to travel, you can make rockets that are water and air powered!

There on the website are the rockets in order of presentation to a class:

Match Rockets

Soda Bottle Rockets

Rocket Matchbox Cars

Visco Fuse Rockets

and the 10 Minute Rocket

Lots of background material for the Rocket part of the Mission to Mars.

Tuesday, January 6, 2009

If you have nothing to work with, how do you build a rocket of any type?

Should you have your students building rockets?

Simple question. Not so simple answer.
Since the science of rockets can be studied using water bottle rockets
I see no immediate safety issue, until you have that rocket launcher in the classroom and have it turned on another student in "horse play." It hunts.

I have looked at size. How about STEPS to bigger rocket designs?
Maybe, match rockets! http://users.bigpond.net.au/mechtoys/matchrocket.html
Cheap enough?
Can you imagine the mayhem in the classroom with this mixture of materials and hormones?

Even NASA has a match rocket sites:

However, I am sure that some will want to take it a bit further and build real rockets, or at least use commericial solid fuel rockets, sold at hobby stores.
With these I see major safety issues for the classroom or even the school parade lot.

Last year, I know of at least one student that was injuried seriously with a commercial, hobby rocket on a school field trip to a "safe location." Real Rockets explode, and you do not want your kid holding it when that happens under any conditions. However, our students deserve to know the science of real rockets.

Here is where I started...

I am showing the movie "October Sky" in my classroom this week.

Today, the Gaza invasion is in its second week with a ground invasion.
I was surprised to see that the Hamas side used a Qassam rocket that was so similiar in design to the one used in the movie...

Wikipedia cites the following source document: Listed as [7]


The Growing Threat of the Kassam Unguided Rockets.

By Dr Azriel Lorber
Ph.D. Aero. Eng, the author of several books on military technology, the most recent being "Misguided Weapons - Technological Failure and Surprise on the Battlefield", published by

The Kassam family of Palestinian home made terror rockets was designed to harass Israel’s civilian population where cross border incursions by suicide bombers proved difficult.
The rockets are extremely simple and as yet are not too effective. Still, they are able to hit major Israeli towns.
The design is based on “Kitchen Technology”, and on commercially available raw materials.
The Hamas would like to see its terror rockets fulfilling the same strategic role as the Hizbullah’s rocket force in Southern Lebanon.
Improvements in quality, reliability and lethality are feasible, but at the cost of making the production infrastructure less covert and more vulnerable.

Ostensibly aimed against the Israeli “Occupation of Palestinian Territory”, the ongoing Palestinian Intifadah (Uprising) targets Israeli civilians within Israel proper, rather than Israeli military targets within the “Occupied Territories”. The Palestinian major instrument of terror is the suicide bomber, used as a human “smart bomb” to zero on and kill Israeli civilians in busses, supermarkets, coffee shops and religious meetings. The success of this tactic is assured wherever the close proximity and lack of physical barriers between Israeli and Palestinians allows easy infiltration of Palestinians into Israel proper.

Where effective physical barriers do exist (such as around the Gaza Strip) the ability of the Palestinian terror organizations to launch suicide attacks into Israel proper is severely curtailed. To overcome this difficulty, the Palestinians have traded maneuverability for firepower, so to speak. Their home made terror rocket, dubbed “Kassam” and fired from within Palestinian held territory, come in lieu of the suicide bomber, yet with the same objective, namely to maximize Israeli civilian casualties.

The worldwide proliferation of artillery rocket technology brought about successful attempts to produce them in makeshift local plants operated by various terror groups. No reliable data exists on production and firing accidents, or even duds, but it is estimated that about two hundred such rockets were successfully fired and this number is sufficient to give headaches to the decision makers on the receiving end. These rockets do not require heavy barrels (but only a couple of lightweight launching rails, see Fig. 1) and thus are easy to transport and conceal. Under suitable condition, even the relatively short range of these weapons is not detrimental if appropriate targets are close enough. The terrorist organizations however are constantly striving to increase their range. For one it will give them more flexibility in choosing their targets or their firing points. Secondly, the potentially longer range can be traded for heavier payloads to shorter ranges.

Fig 1. A Kassam (probably Mk. 2) Rocket at Launch

The following map shows Sderot and Ashkelon, two towns in the south of Israel, and their geographical relation to the Gaza Strip, home to some of the most virulent terrorist organizations in the Middle East.

These Palestinian terror organizations are constantly working to improve their products' range and payload. The initial effort in this field, the Kassam-1, had a short range of couple of kilometers. Design and production were later established also in the Palestinian West Bank but the wide scale effort by the IDF (Operation Defense Wall) after the 2002 Passover atrocity effectively brought this to a halt. The Gaza Strip terrorists in the meantime produced two new types of rockets – see table below:

It should be remembered that some of these numbers are best effort estimates based on a variety of considerations. Another facet of the Palestinian effort is the technical part that is interesting in itself and we will discuss it now.

The propellant in these rockets is based on a 60/40 mixture of Potassium Nitrate and sugar. The final solid fuel grain is of a square cross section (see fig. 2), burning both from the outside and the inside. This grain is sized so that its diagonal fits into the inside diameter of the motor casing. The aft bulkhead, containing the nozzles, is then screwed on and a few spot welds are applied to prevent unscrewing. At best this is a dangerous procedure but apparently they do get away with it.
Fig.2 A Solid Fuel Grain for A Kassam Rocket

The early rockets had a single exhaust nozzle but all later products are equipped with seven nozzles (see Fig. 3). There are two possible reasons for preferring this arrangement: for one, several nozzles diminish the effects of inaccuracies in production of the nozzle, thus contributing to the accuracy of the trajectory. Secondly, it is easier to produce smaller nozzles by direct drilling with no need for (relatively) complicated turning on a lathe. It is interesting to note that these nozzles are not canted (like in the Katyusha rockets) and thus no roll is imparted to these rockets. However, such a modification will require considerable beefing of the launchers and what's more, complicate production. It seems that ease of production is a paramount consideration
Fig 3. The Seven Nozzle Configuration on A Kassam Rocket

Apparently, the earlier multi-nozzle rockets had screwed-on nozzles (see Fig. 4, depicting the location of a broken-off nozzle after impact) but again, probably in order to simplify production, now the nozzles are directly drilled in the rear bulkhead. The material is plain steel and because of the short burn time – on the order of one second – nozzle throat erosion is insignificant.
Fig. 4 The Rear End of A Kassam Rocket With One Nozzle Missing

While in terms of classical rocketry the whole design is less than efficient (it is doubtful if this motor produced an Isp (a measure of the efficiency of a rocket motor) of more than 130 seconds, compared to at least 200 seconds for a "regular" motor, it does serve its purpose.

The warhead is composed of a simple metal shell. The explosive is a mixture of Urea Nitrate and TNT in various ratios, depending mostly on the current availability of TNT that is smuggled in or taken from old military warheads. While again the Urea Nitrate is not an ideal explosive, it can be obtained (like the Potassium Nitrate mentioned above) from suppliers of commercial fertilizers. The fuse is a simple device based on an empty small arms cartridge filled with an explosive booster material operating against a spring-loaded nail. No "safe & arm" mechanism is employed – but it works. Furthermore, there were efforts to improve the lethality of the warheads by equipping them with a nose probe that will enable them to explode several inches above ground.

There are no technical barriers to the moderate scaling-up of both the size and the range of these devices. Admittedly, the real performance of these rockets (range and accuracy) is probable a mystery to the Palestinians themselves since the only firing range they do have is towards the sea. Thus the exact descriptions of fall of shot locations, provided in the news media, probably help the Palestinians quite a lot, by providing range and deviation information. It can be safely assumed that it is only a question of time before such rockets with increased range, and possibly better accuracy, will materialize.

While artillery rockets are not the only terror weapons used by the Terror organizations, from their point of view, they do have some advantages, when compared with other weapons. They are simpler to operate than mortars, have the long reach that mines, by definition, do not have and after firing, their simple launchers can in fact be abandoned. Furthermore, they do not require suicidal volunteers and no amount of security guards will stop them.

The major terror group involved in manufacturing and firing the Kassam family of rockets is the Hamas. The strategic role that the Hamas sees for its rockets is not unlike that of the Hizbullah rockets along the Israeli – Lebanese border. The Hizbullah brandish its Iranian supplied rockets, which can hit Israeli metropolitan areas like Haifa, as a sort of strategic deterrence, allowing it the freedom to harass Israeli targets near the border with impunity. There is little doubt that the Hamas would like to see its own rocket force fulfilling the same role along the perimeter of the Gaza strip, and in the future, perhaps along the borders of the promised Palestinian state.

One ray of hope lies in the fact that while these are terror weapons they are as yet too primitive to be more than of nuisance value, although admittedly with a definite potential to become a real threat. This however will require better performance and especially more numbers, in turn entailing better equipped production facilities, considerable capital outlay and extensive testing which can be detected and acted upon. Monitoring such an effort, coupled with a quick introduction of suitable, active countermeasures may nip this threat in the bud.