S.T.E.M. for the Classroom
Gliding a spaceship back to Earth
Vocabulary
• Altitude: The distance a spacecraft is
above a given point on the ground
• Distance From Spaceport: The ground distance
from the edge of the runway to the spacecraft
• Glide Distance: The distance the Landing
Laser measures to the spacecraft
• Glide Slope (Ø): The angle a spacecraft
makes to the horizontal
• Landing Laser: The laser used to determine
the line-of-sight distance to a spacecraft
Narrative
Most spacecraft returning from space are always
out of propellant. This is because all of the propellant
is used up during the trip into space; consequently,
there is none available for the trip back.
Wait. What? So how does it land?
All machines that have wings can glide, that
is, fly with the engine(s) turned off. Some glide
better than others, but still, they all glide.
The key to gliding in an unpowered spacecraft
is speed. The faster the spacecraft flies through the
atmosphere, the more efficient the wings. Thus a
more efficient glide. Altitude is the other important
component, in that altitude allows the spacecraft to
build up speed if needed. This is why spacecraft come
in with their nose down; they are maintaining their
airspeed. As they cross over the edge of the runway,
the nose is pulled up and the spacecraft flattens out its
glide as air is packed underneath the wings. It’s then
just a simple matter of letting the spacecraft sink to a
gentle touchdown. Once on the ground the nose is kept
in the air “wheelie” fashion, so that speed can be bled
off without using brakes because they can get very hot
very quickly. After the nose comes down on its own, the
brakes can then be (sparingly) applied. Eventually, the
spacecraft rolls to a full stop. Back home once again!
Graph of a spacecraft gliding in for an unpowered glide landing.
Charter School (www.tlcnm.net) were asking the same
question.
We need two pieces of information to get started:
the Glide Distance (GD) and the Glide Slope (Ø).
We will use the Landing Laser to determine this
distance and the angle. It will take a “snapshot”
of this information whenever we need.
Once we have Glide Distance and Glide
Slope, which is to say, once we have a side and
an angle, we can form a Right Triangle.
Analysis
So, at any point in the glide, what was the Altitude
and the Distance from the Spaceport of the spacecraft
that just landed? Good question! Why, just the other day
some high school students at The Learning Community
A Pythagorean Triangle showing the relationship between altitude, glide slope(Ø),
and the distance from the Spaceport.
For a more in-depth treatment of this high
school project by Joe Maness & Rich Holtzin
visit www.stemfortheclassroom.com.
Therefore, we can use trigonometric identities to
solve for the other two sides. We also see that the Glide
Distance becomes the hypotenuse of the right triangle.
Moreover, since cosine is defined as the adjacent side
44
44
www.RocketSTEM .org