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National Aeronautics and 

Space Administration

DATE

NASA STEM

NASA Student Launch ARW 

Recovery Systems

PRESENTED BY NASA Student Launch

DATE July 24, 2023
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Parachutes:

The most used recovery device in high powered rocketry

A high drag device that slows down the high-speed descent of the rocket by 

producing a force that opposes the weight of the rocket

The effectiveness (or drag) of a parachute depends on: 

• Velocity

• Air density

• Surface or “reference” area

• Drag coefficient

Typically have three major features:

• Canopy 

• Support lines (shroud lines) 

• Steel connector link (swivels, quick links, eyebolts)

Hardware: Parachutes

Drag coefficient:

A dimensionless quantity that is used to quantify the 

drag of resistance of an object in a fluid environment 

such as air

Parachute Protectors:

A flameproof Aramid cloth or Kevlar cloth will protect 

the parachute from these hot gases and burning 

debris. 

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Parachute Protectors:

Nylon is susceptible to melting and charring

Necessary to protect parachutes

Typical materials for Parachute Protectors:

• Aramid/Kevlar

• Kevlar/Fiberglass

Other Options:

• Pistons

• Deployment Bags

Hardware: Parachute Protectors

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Recovery Harness:

A long length of cord that attaches structural components that separate as 

part of the recovery system

Each end is typically secured by quick-link to a U-bolt or eye-bolt that is rigidly 

mounted to a bulk plate on an avionics bay, nose cone, or booster

The length of shock cord required will be the subject or empirical testing and 

evaluation

Your workshop rocket has 12 feet of shock cord

An L3 type rocket may require more than 100 feet or shock cord

Rule of thumb is each section of shock cord should be 2-3 times the length of 

your rocket

Typical materials for shock cords:

• Aramid/Kevlar

• Kevlar/Fiberglass

• Nylon

Hardware: Recovery Harness

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Considerations:

Economics

Strength

Stretchiness

Durability

Preference

Hint: Be weary of 

manufacturer ratings, size 

is usually your best 

reference.

Shock Cords

Nylon Kevlar

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Quick Links:

Make connecting and rigging a recovery system very easy

Many different types of quick links available commercially

Always use quick-links with a locking gate

Take care in choosing a quick-link that will safely carry the maximum 

expected load 

Too small of a quick-link may yield under heavy loading when the 

main parachute opens

Hardware: Quick Links

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Eye-Bolts & U-Bolts:

Hard points on rocket’s structures for attaching recovery system

Typically mounted on bulk plates and/or centering rings

U-bolts are preferred on large rockets

Eye-bolts must be closed and/or welded closed, bent eyebolts are 

not permitted 

Hardware: Eye Bolts and U-Bolts 

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Other Hardware

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A typical Single Event Recovery System ejects a 

parachute or streamer at apogee

This can most commonly be achieved by using a motor 

ejection charge

Most low to mid power rocket motors have this 

capability

At motor ignition, the propellant and a delay grain 

begin to slowly burn

Once it burns through, the ejection charge is set off and 

the parachute is deployed

SERS is the simplest recovery system and is good for 

low altitude flights on small launch fields and highaltitude flight on very large launch fields

Single Event Recovery Systems (SERS)

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Your Student Launch Project rocket is 

required to use a Dual Event 

Recovery System

1st event at apogee 

2nd event at much lower altitude

Typically, 500-1000 feet Above Ground 

Level (AGL)

Requires electronics 

Significantly reduces the recovery area 

Dual Event Recovery System (DERS)

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Dual Event Recovery System (DERS)

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The Avionics Bay

Subsystem of a high-powered rocket that typically contains altimeters, batteries, and switches

A typical E-Bay is comprised of three structural components: the housing, a forward and aft end-cap and an avionics sled

Dual Event Recovery System (DERS)

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Avionics Bay Housing:

Typically built from a coupler tube

Can have a collar (switch band) made from a segment of airframe 

epoxied to the middle of the couple

Allows direct access to the switches that power on the altimeters

Supports static pressure ports that equalize the housing’s interior 

pressure with the exterior atmosphere

Generally, when joining airframes with a coupler, the coupler should 

extend at least one airframe diameter into each joined segment

Dual Event Recovery System (DERS)

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End Caps (i.e., removable bulkheads):

Close out the housing separating the rocket’s volumes

Support the recovery harness hard mounts, charge cups, 

and all-threads

The all-threads act as a two-force member that connect 

both end-caps and carry the recovery harness load through 

the E-Bay

End-caps should create a good seal around the end of the 

housing to prevent hot gas seepage from the ejection 

charges 

Typical Materials:

• G-10 fiberglass 

• Plywood

Dual Event Recovery System (DERS)

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Avionics Sled

Sliding onto the all threads that connect the end plates -

like a sled

The avionics electronics, batteries, and switches are 

mounted to the sled and wired together to form systems

Typical Materials:

• G-10 fiberglass

• Plywood

Dual Event Recovery System (DERS)

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DERS Recovery Wiring Schematic

Recovery Electronics Diagram (Required for Each milestone):

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Altimeters:

Dual Event Recovery Systems require the use of electronic devices called 

Altimeters

Determine altitude and initiate recovery events

Your Student Launch Project rocket shall have no less than two 

commercially available, independent, redundant altimeters

It is recommended that each altimeter have a dedicated battery and on-off 

switch.

• This setup will greatly reduce the likelihood of a recovery system failure

Typically, altimeters require 9V-12V of electricity

Altimeters, generally inside of the rocket’s avionics bay, need to sample the 

outside air pressure

Your rocket will need static pressure port along the outside to allow the inside 

pressure to equalize to the outside pressure

Recovery Electronics: Altimeters

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Batteries:

The NASA Student Launch Projects official handbook requires that your rocket have 

a minimum pad stay time of three hours

That means that your electronics should be able to remain switched on and reliably operate if the rocket remains on 

the pad for up to one hour on the pad before launch

Two main types of batteries:

Primary - designed to be used once and discarded when they are exhausted

• Cost less than secondary batteries

• Don’t require sophisticated chargers to recharge them

• Lower “self discharge” rates than secondary batteries

Secondary - designed to be rechargeable and used multiple times

• Weigh less than primary batteries

• Manufacturers can shape them however they please

• Greatly increased run time

Improper use or charging of some secondary batteries can result in fire or explosion

Recovery Electronics: Batteries

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Switches:

Each altimeter will be armed by a dedicated mechanical arming switch that is accessible 

from the exterior of the rocket airframe when the rocket is in the launch configuration on 

the launch pad. 

Safety feature for pressure & g-switch activated recovery systems

Maximizes battery life

Surface mounted to airframe or mounted inside rocket with access hole or panel

Two categories of switches typically used on high powered rockets: 

• Single Pole Single Throw (SPST), is a simple of-off switch where the two terminals are either 

connected or disconnected from each other

• Dual Pole Single Throw (DPST) is equivalent to two SPST switches controlled by a single 

mechanism.

In these two categories, there are toggle switches, push button switches, and selector switches

Note: We do not allow magnetic switches

Recovery Electronics: Switches

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A black powder charge is the most common and reliable method 

of ejecting a parachute from your rocket

Hot gases that pressurize the rocket’s airframe and exert a net 

force on the bulk plate of the nose cone

This net force will eject the nose cone, shock cord, and 

parachute out of the rocket airframe

This all happens because the rocket is obeying the Idea Gas Law

• P is the absolute pressure of the gas

• V is the volume occupied by the gas

• N is the amount of substance (black powder)

• R is the gas constant

• T is the absolute temperature

Ejection Charge Sizing

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The equation can be reordered to solve for N directly and known values substituted

Online calculators can help calculate amount of black powder to start with for testing purposes

The design pressure is determined by the desired net force on a surface divided by the area of that surface

Typical net force values for a 4-inch diameter rocket range from 100 lbf - 200 lbf

• This translates to a typical pressure range of 8psi – 16psi

Black Powder charge amounts are typically reported in the unit grams

• Recall that there are 454 grams in 1 pound

The reduced equation for this case, states that 0.1 grams of Black Powder is needed for every 1 inch of airframe containing 

the recovery system

• If L = 20 inches, then 2.0 grams of black powder is needed to eject the recovery system

Ejection Charge Sizing

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Universal initiator of many rocketry pyrotechnics and motors

Typically made from a thin nichrome (nickel-chromium) wire 

laminated to a small nonconductive flake of fiberglass

Each end is soldered to one wire of a two-conductor solid core 

copper shooter wire

The nichrome bridge is dipped into a pyrogen formula that dries 

hard and looks like a match, hence the name

Typically, high current or low current

Kits for making your own e-matches can be purchased on 

the internet – NOT TO BE USED IN NASA STUDENT 

LAUNCH

Note: Some distributors use other names.

E-Matches

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Generally used on mid to high powered rockets to prevent dynamic separation or premature/incomplete deployment of 

the recovery system

Dynamic separation occurs when a rockets separates in the coasting phase because the different sections are 

decelerating at different speeds

An example would be when a rocket’s booster section separates from the forward airframe or nose cone because the 

fin drag, or the base drag effects creates a significant enough force to overcome the frictional force keeping the sections 

together

Rocket builders generally use small nylon machine screws as shear pins

• #2-56 nylon machine screw has an average shear strength of 25 lbs.

• #4-40 nylon machine screw has an average shear strength of 40 lbs.

Shear Pins

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Vacuum Chamber Testing:

Proves pressure-based rocket altimeters are functional

Can be as simple as a single altimeter in a mason jar using a 

marinade syringe to pull the air out

Or as complex as a full systems test of the entire rocket 

recovery system

A simple visual indicator of an altimeter’s health can be a 

Christmas tree light wired into the ejection charge terminal 

blocks

Recovery System Testing

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Ejection Charge Testing:

Conduct several ejection charge tests before flight

Best way to assess:

• Ejection charges are of sufficient size

• Assess the configuration effectiveness 

Success criteria:

• Both main and drogue systems deploy as expected 

• The parachutes extract from the airframe

• The parachutes and shock cords are suitably protected from the ejection 

charge

The tests prove the design is ready for flight

Note: Successful ground ejection test does not ensure successful inflight separation

• Strong ejection on the ground will help ensure successful deployment inflight

Recovery System Testing

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Questions? 
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