The General Gas Law and the Apollo AstronautsStanley K. Derby

Western Michigan University, Kalamazoo, Mich. 49001

Astronauts Chaffee, Grissom and White died in the tragic spacecapsule fire of January 27,1967. It was reported that the official deathcertificates of the crew members listed the cause of death as asphyxia-tion due to smoke inhalation due to the fire.Any science teacher who has dropped a glowing piece of steel wool

into a jar of oxygen may ponder on the conclusion of death by asphyx-iation.The reported sequence of events was as follows:

6:31:03 Chaffee reports a fire in the spacecraft.6:31:03 Cabin temperature starts to rise.6:31:09 White repeats report of fire in the cockpit. Cabin pres-

sure starts to rise.6:31:12 Cabin temperature starts to increase rapidly.6:31:17 Cabin pressure reaches a level of about 29 pounds per

square inch. Cabin ruptures.

One may conclude from these data that the pressure rose from ap-proximately one atmosphere to two atmospheres in a time span of 14seconds. It is possible through the general gas law to compute thetemperature change which occurred during this short time interval.One form of the general gas law may be expressed as,

PfVf PiVi��� == �� General Gas LawTf T,

where P, V, and T represent pressure, volume and temperature. Thesubscripts i and / designate the initial and final states respectively.This general gas law expression, of course, may be reduced to

P^A-Tf Ti

Gay-Lussac Law

by the assumption of constant space cabin volume.We may solve the above expression for the final temperature to

obtain

T’-^T’From this one may infer that doubling the pressure doubles the Kel-vin temperature. Or, given a reported initial pressure of 16 p.s.L, afinal pressure of 29 p.s.L, and an initial temperature of 75°F.^25°C.

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594 School Science and Mathematics

== 298°K. we may calculate the space cabin temperature

/PA /29 psi\Tf == ( �) Ti = ( �� ) (298°K.) == 540°K.\PJ V^pst/’

Now 5400K.=2670C.==5130F. Thus the Fahrenheit temperature atthe time of rupture of the spacecraft was of the order of 500°F. andstill rising.The space cabin was initially filled with pure oxygen. It is of

interest to determine what fraction of the original oxygen remainedunconsumed at the time the space cabin ruptured. To make thiscalculation we may guess the available space cabin volume to be inthe neighborhood of 3000 liters. This volume of oxygen would corres-pond to 134 moles or about 4.3 Kilograms.The amount of heat energy necessary to raise the temperature of

4300 grams of oxygen from 25°C. to 267°C. may be calculated from

H=CMAT

where H is the energy required, C= 0.218 cal./gm.°C. is the thermalcapacity of oxygen, M is the mass of oxygen and AT is the change intemperature. Thus H= (0.218 cal./gm.°C.)(4300 gm.)(267-25°C.)==227,000 calories.Now, considering the space cabin as constructed from assorted

metals and carbon-containing compounds, it is informative to checkthe heat of formation of a few oxides.From Table 1 we see that 3 Kilocalories/gm of oxygen might be a

conservative estimate of the rate of heat production in this combus-tion process. Therefore, to liberate approximately 227 Kilocaloriesof heat would require a combustion of

TABLE 1. HEAT OF FORMATION or RELEVANT OXIDES

Heat of formationHeat of formationOxide in Kcal./mole ofin Kcal./gram of

oxide formedcombined oxygen

CuOC02MgOFe20sA1203

3594145190399

2.182.949.053.9513.3

227 Kcol.������� == 72.5 grams of oxygen.3 Kcal./gm.

Inverse Square Law 595

We interpret this number to mean that 72.5/4300 of the originalquantity of oxygen had been burned. This amounts to approximately2%. In other words the space cabin temperature had reached 500°F.in 14 seconds with approximately 98% of the oxygen yet to beburned.

Little wonder that the rescue crews were driven away by the heatfor more than five minutes.

Dynamic Demonstration of the Inverse SquareLaw with a Crookes Radiometer

George K. EstokDept. of Chemistry, St. Edward’s University, Austin, Texas 78704

A Crookes radiometer,* a 60 watt frosted light bulb, and a footruler were used for this demonstration. The number of rotations perminute of the radiometer wheel was determined for different dis-tances from the light source. This number was found to be inverselyproportional to the square of the distance. Counting rotations byeye was easily accomplished because there was an observable pre-cession of the tip of the rotor hub. The formula RcP^k was used.

distance (d) Rotations per min. (R) RXd2 k

0.50ft. 130 130X0.25 330.75 61 61X0.56 341.00 34 34X1.00 341.25 21 21X1.56 331.50 14.5 14.5X2.25 33

The values of k are excellent for such a simple and crude experi-ment.

* Note: Old or defective radiometers are not likely to give satisfactory results.

SAFER NEW ANESTHETICA new general anesthetic, ketamine hydrochloride, is described as the safest

ever developed. This is the opinion of Dr. Guenter Corssen, chairman of theMedical College of Alabamans department of anesthesiology."One of the reasons the drug is so safe," Dr. Corssen says, "is the absence of

impaired respiratory function."Ketamine is neither a barbiturate nor a narcotic, and unlike conventional

anesthetics, it does not depress all areas of the central nervous system. It leavesthe patient with his eyes open but disconnected from his surroundings and unre-sponsive to pain.