Nuts and Volts - February 2009

BILL BROWN

Bill Brown, the father of modern American near space ballooning, was next. Bill’s presentation covered a variety of topics because he basically is a master experimenter.

Bill is also a fan of long duration near space flights. Normally, a flight like this can only be accomplished with an expensive polyethylene balloon. However, Bill has perfected techniques involving less expensive latex weather balloons. In one of his techniques, he seals the balloon’s neck with a PVC pipe containing a 1/16 inch diameter hole. The hole lets helium slowly vent out of the balloon, gradually slowing down its ascent rate. The decrease in ascent rate is so slow that the balloon still reaches near space altitudes before the sun’s ultraviolet rays degrade the balloon to the point of bursting. One of Bill’s flights reached an altitude of 107,000 feet in its 17-1/2 hour flight (compared to a nominal 100 miles for a flight like this).

Bill recommends launching a flight like this in the spring and autumn when the stratospheric winds begin changing their direction (this is called the stratospheric turn around). That way, the balloon drifts slowly and recovery takes place closer to the launch site rather than across many miles.

One of the neatest things Bill presented this year was the Find Me Spot, a personal GPS tracker. As he explained, SPOT transmits its GPS location to Global Star satellites every 10 minutes. From experience, Bill discovered that it didn’t transmit its position above 60,000 feet. However, once the near spacecraft carrying Find Me Spot descended below this altitude, Find Me Spot began transmitting its location again. Even upside down, SPOT transmitted its GPS position to the Global Star Satellite overhead. While a bit spendy at $169 for the unit and $150 annual fee for unlimited use, SPOT may be the ultimate insurance policy for a near spacecraft.

■ Find Me Spot, the personal satellite tracker. (Carry one of these with you and friends will know where you’re at every 10 minutes.)

■ Bill Brown discussing his many near space activities.

EDGE OF SPACE SCIENCE

Mike Morgan of Edge of Space Sciences (EOSS) was the next speaker. He led a discussion about using hydrogen to fill latex weather balloons.

Like many commodities, helium prices have recently begun to rise (pun intended). While helium is the second most abundant element in the universe, its existence on earth comes only from the decay of radioactive isotopes underground. As natural gas reserves are exhausted or become too costly to pump, the availability of helium will continue to decrease, further raising its cost.

When hydrogen-filled balloons get mentioned, people invariably think of the Hindenburg. However, hydrogen wasn’t the problem with this great airship; the problem was its flammable skin. As long as proper safeguards are used, hydrogen is a safe filling gas for weather balloons. This doesn’t mean there aren’t risks associated with hydrogen.

Unlike helium, hydrogen is flammable in concentrations ranging from 4% to 74% (a very wide range). Hydrogen requires low energy to ignite and may even self-ignite with a little static electricity. Its flame is nearly invisible to the naked eye and it burns hot.

Mike recommended to never vent hydrogen from a tank into the atmosphere. So, never drain a tank of hydrogen by opening its valve;

instead, bring it back to the welding supplier for disposal.

Other suggestions were to use a single tank at a time to fill a balloon; do not connect several tanks together into a single manifold. Use stainless steel or brass fittings; not plastic ones as they can generate static discharge as dry hydrogen flows through them.

Ground all filling equipment with at least three stakes to the ground. This includes grounding the person handling the balloon filler with a grounding strap. In addition, fill the balloon slowly, as a lower flow rate decreases the chances of electrostatic build-up.