Welcome to the NASA High Power Rocketry Video Series.
In this video, we'll be discussing
payloads and avionics.
One of the most exciting parts of high-power rocketry
is that high-power rockets can fly systems
that perform certain tests.
We call these payloads.
The payloads can be used for recovery system, an engineering
package, a tracking system to locate the rocket, and /
or a scientific experiment.
One of the most basic payloads is an altimeter
to record the altitude of the rocket in flight.
The altimeter needs a power supply and a switch
in order to be turned on.
Since most altimeters sense barometric pressure,
they use a pressure transducer to determine the altitude
based on the change in pressure since the rocket left
the ground.
For this reason, it is important to have a small hole in the air
frame so that the altimeter will be
able to sense the ambient pressure outside of the rocket.
A few altimeters used in high-power rocketry
are accelerometer based and use the acceleration data
to determine the altitude.
Since these altimeters do not measure the air pressure,
is not necessary to have a hole in the air frame.
Hobby rocketry altimeters are very small
and can fit in spaces as small as 1 by 3 inches.
For this reason, small altimeters
are commonly flown as payloads to measure rocket height,
even if the altimeters are not used to control recovery system
events.
Another example of a payload is a set
of trackers to locate the rocket during its flight.
The units transmit a radio frequency
to a receiver on the ground.
Trackers can operate in a few different ways,
and we will discuss the two most common.
The first is simple radio frequency transmission.
With radio frequency transmission,
a unit on the rocket transmits a radio wave
at a certain frequency and a handheld receiver on the ground
detects the transmission.
The ground unit emits an audible signal
that is loudest when pointing toward the rocket.
By walking in the direction that gives the loudest tones,
the user can find the rocket.
The other type of tracker commonly used
is a global positioning system-based unit.
These units are often referred to simply as GPS.
There are a few common methods in which GPS systems work.
In one method, a transmitting unit on the rocket
sends and receives signals to GPS satellites
orbiting the earth.
These satellites transmit a signal
that gives time and satellite position
data to a ground-based unit.
The ground-based unit then performs
a series of mathematical algorithms
to calculate the position of the transmitter on the rocket.
The position of the rocket is displayed on I hand unit
so the user can see where the rocket has landed.
With the other method, the unit on the rocket
acts as both a receiver and a transmitter.
The unit on the rocket receives the position data
from the satellites, does the calculations,
and then transmits the position data
to a ground-based receiver.
Although units that transmit a signal via a simple radio
frequency transmission or GPS transmission
are useful in locating the rocket after a flight,
there are a few things to keep in mind
to ensure the safety of the rocket,
surrounding property, and most importantly, yourself
and others.
The trackers transmit energy in the form of radio waves.
There are other parts of your rocket
that are affected by this energy and steps
need to be taken to ensure that no accidents happen.
Your recovery system components can
be greatly affected by the radio frequency
from the transmitters.
The electromagnetic interference from radio waves
can adversely affect the sensor data on the altimeter,
and the altimeter may incorrectly read altitude data.
This becomes problematic when the interference is bad enough
that the altimeter incorrectly senses
that the rocket is at the altitude for parachute
deployment.
When this happens, the altimeter sends the signal
to ignite the electric match, which
ignites the black powder ejection charge
and deploys the parachute.
If this happens on the ground, the ejection charge gases
and moving airframe components can cause properly damage
and serious personal injury.
Also, if the electromagnetic interference is strong enough,
the resulting energy can actually
ignite the electric matches without a signal
from the altimeters, thus deploying the parachutes.
Another less-hazardous effect is that
the electromagnetic interference of one tracking device
could interfere with the output of another transmitting device.
There are ways to mitigate the effects of the interference
on other parts of the rocket.
First, the power output of any transmitter
should be only high enough for the unit to work effectively.
If a GPS transmitter can operate with a power
output of 100 milliwatts, then don't use a higher output.
The higher the power output, the higher
the likelihood of radio frequency interference.
Second, create physical distance between transmitting
devices and components that are sensitive to radio frequency
energy.
If the recovery system circuitry is in the middle of the rocket,
it is a good idea to put a transmitting device
in a separate and isolated part of the rocket.
The nose cone is a popular place for rocketeers to put
tracking system transmitters.
This creates enough physical distance
between the transmitters and recovery system circuitry
that assuming proper transmitter power output,
there should be no interference between the components.
A third way to prevent inadvertent radio frequency
interference is to actively shield the components.
A popular and inexpensive way to shield the components
is to line the inside the altimeter
bay with a metallic material, such as aluminum foil.
In addition to payload packages that
are used for altitude recording and tracking,
there are a multitude of possible payload options
used for scientific or engineering purposes.
These can include atmospheric science, biology, anatomy
and human factors, micro-gravity, aerodynamics,
control systems, and many other options.
Some of the most popular rocket payloads
are for atmospheric measurement.
These payloads may measure temperature, pressure,
humidity, solar radiance, or radiation.
Sensors for these measurements are readily available,
easy to use, and easy to integrate into the rock.
Many student rocket teams fly biology experiments.
Plants and invertebrates can be flown
to test the effects of the launch forces
on the long-term growth and genetic characteristics
of the test subjects.
Anatomy experiments have included
testing the capillary action of blood
during the acceleration and micro-gravity
portion of the flight.
These payloads support the research
of long-term human space flight.
Some of the more challenging payloads
are micro-gravity payloads.
During the brief period of micro-gravity seen at apogee
during the first few seconds of free fall,
teams may fly fluid dynamic experiments, control system
experiments, gas dynamic experiments,
and other micro-gravity experiments.
Some complicated payloads actually
deploy away from the rocket at some point during the flight.
These payloads can be scientific in nature,
but often are engineering based.
One example is a package that is instrumented to sense
atmospheric properties.
Another example is a deployable unmanned aerial vehicles.
These can include gliders, helicopters,
or airplanes that can each have its own payload package.
While deployable payloads are exciting,
they complicate the recovery process.
One must ensure the deployable payloads
have a dedicated and reliable recovery mechanism that
is flight worthy.
When choosing a payload, it is important to keep in mind
that the range safety officer has the authority
to make the final decision on whether or not a project flies.
As such, it is important to communicate
clearly and thoroughly about your intentions
to fly any payload.
If flying the payload creates a flight profile that
is outside the realm of normal high-power rocketry flight,
it is good practice to contact the local clubs prefect
and range safety officer well ahead of the day of the flight.
Describe the project in mind and answer
any questions they may have.
Safety is paramount, and any questions
about a particular project or an outright refusal
to allow a particular project to fly because of elevated risk
should be observed.
Remember, the range safety officer is the final authority.
Thank you for watching this NASA High Power Rocketry Video
Series.