The Power of Helios
It's
a Bird, It's a Plane...
NASA's Helios aircraft
doesn't look or move like a regular airplane. Its winglike body
stretches 247 feet across, longer than the wingspan of a Boeing
747. Once in the air, Helios flexes and moves like a kite.
How did Helios harness
solar power to become the world's highest flying plane?
Scientists launched Helios
in Hawaii on the morning of August 13, 2001, to take advantage of
a long, sunny day. Sunlight absorbed by its 65,000 solar cells powered
the tiny, 2-hp electric engines attached to each of its 14 propellers,
keeping the experimental plane rising into the air.
The system worked so
well that Helios broke the 80,200-foot altitude record for propeller-driven
aircraft and the 85,068-foot record for all nonrocket craft. By
day's end, Helios had reached 96,500 feet — three times higher
than the altitude a commercial jet normally flys at. Thinning
air and decreasing sunlight convinced researchers that the craft
couldn't rise an additional 3,500 feet to meet their goal of 100,000
feet, so they returned the craft to Earth via remote control.
Scaling
New Heights
Scientists
believe that Helios could eventually reach an altitude of 103,000
feet under ideal weather conditions. It fell short of that goal
with this flight, but NASA researchers are heartened by the experiment.
At 96,500 feet,
Helios was
flying in the thin air at the edge of Earth's atmosphere. Researchers
believe that the data collected by Helios will help them design
an aircraft that can fly in the similar atmosphere of Mars. A
solar-powered aircraft flying over Mars could survey a great expanse
of that planet, much more so than a vehicle on the ground.
Scientists also believe
that, by using solar energy, Helios could potentially stay aloft
for months at a time. This could enable it to be used as a low-cost
alternative to environmental monitoring satellites as well as communications
satellites. Such aircraft could provide more efficient broadcast
feeds and high-speed Internet access.
Build
a Solar Collector
The Sun is a massive source
of energy, glowing at a toasty 27 million °F (15 million °C) at
its center. But, the Sun is 93 million miles away — how does its
energy reach the Earth?
The energy travels through
space as radiation. When some of the radiation arrives here eight
minutes after leaving the Sun, it changes form again, and we feel
the warmth on our skin. See
how it works for yourself by building a solar collector and using
it to cook food.
- How solar collection
works: Sunlight is visible radiation of energy from the Sun.
When the light shines on any object, some of the energy gets absorbed
and raises the energy of the object. For the solar collector to
work well, it must:
- Absorb energy
from the sunlight
- Keep heat from
escaping by providing some kind of enclosure
- How to build your
collector: Finding the best materials for your oven is critical.
What materials are good at absorbing heat from sunlight? Foil?
Paper? Wood? Plastic? What colors work best? Light? Dark? The
way to find out is to try different materials, and measure the
results in your own solar collector.
- Find a container.
You might use a shoebox, plastic bucket or jar, paper bag,
milk carton, yogurt tub, or cereal box. Avoid anything made
of glass!
- Choose a transparent
material that will allow sunlight to shine into your collector.
Remember all of the Sun’s rays needs to shine through the
material.
- Figure out how
to measure the air temperature inside the collector. You need
to be able either to take the thermometer out of the collector
and replace it without tearing a hole or to locate the thermometer
in a place where you can read it easily. (Cellophane tape
can be used to plug holes around a thermometer opening.)
- Line the inside
surfaces of the collector. The sides of the collector should
absorb as much sunlight as possible.
- Make sure you
hold the heat inside the collector. Cold air can enter the
collector through holes, and warm air can escape through outside
surfaces.
- Point your collector
so that it catches the Sun’s rays. Try to catch as much sunshine
as you can.
- How to measure
your results: The goal of your solar collector is to collect
energy and raise the air temperature inside the collector as much
as possible. You can print out this page and write your measurements
in the table below.
- First, put your
collector in a shady spot. Let it sit for10minutes
so the temperature stabilizes. Measure the temperature inside
your collector with a thermometer, and record the shade
temperature.
- Next, put your
collector in direct sunlight. Let it sit for 10 minutes before
measuring the inside temperature with the thermometer. Write
down the direct sunlight temperature.
- Calculate the
temperature increase. The temperature increase is the
direct sunlight temperature minus the shade temperature.
All of the participants in Catching Sunshine have agreed
to compare their temperature increases using °C. If you
measured your increase in °F, use the formula to convert
Fahrenheit to Celsius:
(°F
- 32) x 5/9 = °C
| |
°F
|
°C
|
| Shade Temperature
|
|
|
| Direct
Sunlight Temperature |
|
|
| Temperature
Increase |
|
|
- How to compare
collectors: Which absorbing material works best? What are
the best times and locations to catch sunlight?
Learn More
|
