The backstory is that I recently attended a party of former Kentucky Fried Chicken research and development engineers with my husband, and they brought several pieces of memorabilia to reminisce about their work.
An interesting incubator caught my attention, and I learned that they were instrumental in helping a young man from Lafayette, Indiana launch his science project.
In 1981, ninth grader John Vellinger had a question that he wanted to test: How does gravity affect chicken embryo development? He knew that gravity pulled the yolk, the developing chick’s food source, to the bottom of the egg, but hens would naturally move their eggs to keep the yolk from settling in one place. Incubated eggs also need to be turned regularly for healthy chicks. His hypothesis was that an environment without gravity would produce a more nourished chick. He thought this information would be valuable if space colonization ever occurred.
Vellinger submitted his project into a contest sponsored by NASA and the National Science Teachers Association, and after two years of tweaking and resubmission, his project was chosen in 1983.
KFC sponsored the project for several years, and their technology team helped Vellinger build a space-shuttle incubator.
Thirty-two eggs were first launched on the fateful Challenger on January 28, 1986. Vellinger and the KFC persevered, and 32 new eggs were launched again in March 1989; they incubated in space for 5 days under the watch of the astronaut crew.
The space eggs and the 32 eggs that remained on earth were examined once they returned to note any differences. A few of the eggs were allowed to hatch, and became project mascots.
I loved learning about this project not only because it was tied to agriculture, but that Vellinger and the team were meticulous in applying the scientific method to answer a question.
Here is John's narration of his experiment from the KFC "Chix in Space" curriculum booklet
(Note: this was written prior to the first launch on the Challenger. The experiment was modified for the Discovery. The eggs were in space for only 5 days instead of 6).
On earth, gravity pulls the yolk, which is the embryo's food source, to the bottom of the egg. The movement of the hen in the next constantly turns the egg and keeps the yolk from sticking to the bottom. But in space, without the force or gravity pulling it downward, the yolk should remain in the center of the egg. Thus, the weightless environment of space might produce a better nourished chicken.
From the time an egg is laid, it takes about 21 days for the chick to hatch. The embryo's bones, muscles, organs, and nerves develop during the first 11 days; the last 10 days are devoted to growth.
Half of the 32 fertile eggs that go aboard the space shuttle will be two days old; the other half will be 12 days old.
At the end of the mission, they'll be eight and 18 days old, which will allow us to study two important stages of embryo development. Not until the chicks hatch will we learn whether zero-gravity is an optimal environment for chicken embryo development.
This experiment may help scientists understand more about the effects of weightlessness on organisms. It can also help us begin to find out if we can grow food sources such as chickens in space and whether humans can someday raise families there.
On earth, the normal force of gravity is expressed as 1 g. The phenomenon of gravity was first described in 1686 by Sir Isaac Newton after observing falling objects. At 1 g, an object would fall at the rate of 9.8 meters per second x 9.8 meters per second, or 9.8 meters per second squared. This is expressed as Fw=mg. In space, at zero g, the object does not fall of its own accord. Instead, it remains suspended in air.
Maybe you have seen pictures of astronauts floating around the cabin of the space shuttle during a mission. Many things change in a weightless environment, including some of the basic scientific assumptions that apply on earth.
For example, without gravity, hot air does not rise. Long hair does not hang to the shoulders, but floats in the air. And the yolk of an egg is suspended in its center. The viscosity of the albumen will keep it floating upward, and the lack of gravity will prevent it from falling to the bottom.
During the launching of the space shuttle, the extra force needed to create liftoff results in a different level of gravitational force--neither zero g nor 1 g, but 3.3 g's, or three and one-thirds times as heavy as the force of gravity on earth. This means an object would fall 3.3 times faster than it normally does.
To protect the eggs during the mission, I've designed and built a 19" x 15" x 9" incubator, which will simulate their development in the nest. During the mission, I'll be incubating a control group of eggs on earth under the exact same conditions, in an identical incubator. Just one thing will be different: because they will be in a gravity environment, I'll have to turn them by hand to simulate the hen's movement on the nest.
To be sure the incubator would control every variable except weightless, I've had to do a number of tests incubation fertile chicken eggs.
For example, I put an incubator full of fertile eggs onto a special machine at Johnson Space Center in Houston that simulates the conditions of liftoff. The incubator has a system of springs and shock absorbers that work on the same principle as a car, and protects the fragile embryos from the conditions created during launch.
Then I hatched the chicks, and they were perfectly normal, which told me that I had controlled the variables of vibration and 3.3 g force.
To protect the eggs even further, I tested different kinds of synthetic foams. It was critical that the foam did not block too much oxygen, since the egg needs 21 percent of its ambient atmosphere to be oxygen. I hatched different batches of chicks cradled with foams of different porosity and found one that allowed just as much oxygen to pass through the egg shell as no foam at all.
Other variables that had to be eliminated were changes in humidity and temperature. The optimum is a temperature of 37.5 C (99.5 F) and 65 percent relative humidity. The incubator has a heating system that works the same way as a furnace and thermostat in your house. Since hot air doesn't rise in zero g, the incubator has a tiny fan that draws air uniformly through the eggs. The incubator will draw its power from the space shuttle's power system.
Since there is not enough oxygen in the incubator for a the full six days, the crew will have to open its hatch door periodically and allow more oxygen to enter the space shuttle's cabin. As the door is opened, humidity escapes; so they will be replenishing the humidity with moistened capillary pads that work in the same way as a sponge.
The astronauts will record the temperature and humidity in the incubator, as well as their observations about the condition of the eggs.
When the [space shuttle] returns to earth, the incubator will be removed and flown to Purdue University's agriculture science laboratories. There, with the help of embryologists and other experts, I will look at the chicks that went up in space and compare them with the control group.
What were the results?
Here is the abstract from the research:
Avian Embryogenesis in Microgravity Aboard Shuttle STS-29: Embryonic Survival and Measurement of Developmental Age – This investigation determined the influence of a 5-day Earth-orbital flight upon development of chick embryos (Gallus domesticus). All control eggs were either normally developed when opened or they manifested in a normal hatch. All eight of the older experimental embryos, opened upon the shuttle’s return, were viable and appeared by external features normally developed for 14-day embryos. All eight of the younger experimental embryos, opened after a 7-day incubation, had stopped development at these stages: one at 6.5 day; two at 4-day; two at 3.5 day; one at 3-day; and two eggs revealed no embryos. The eight younger experimental embryos, incubated until hatch date, did not pip and, and when opened, had stopped development at these stages: two at 5-day; two at 4-day; and four eggs revealed no embryos. It is concluded that the microgravity of this mission does not adversely affect survivability of chick embryos during days 9-14 incubation. Younger embryos did continue their incubation in orbit, but were adversely susceptible to microgravity. The variation in time of embryo death in this younger experimental group may in part be due to variation in age (max. 12 hr) at the beginning of their incubation.
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