Safety and rules

Read this before you buy parts, not after you have built something.

Nothing here replaces your club's safety officer or your Range Safety Officer. If someone standing at the range contradicts this page, they win.

What oApogee does not do

oApogee is a passive instrumentation payload. It does not fire ejection charges, control deployment, ignite motors, or command any pyrotechnic device.

This is a design boundary, not a missing feature, and the reason is the difference in consequences. If an instrumentation payload fails, you lose data. If a deployment controller fails, the rocket comes in ballistic, or the charge fires on the pad while somebody is standing at it. A payload that can only observe means the worst outcome of any bug in this project is a disappointing graph. Deployment control belongs to high power rocketry, flown under a certification programme that exists because those consequences are real.

Your recovery system is the motor's ejection charge and delay grain, exactly as it was before you added a payload. oApogee does not change it, interact with it, or know it happened except as a jolt in the accelerometer trace. So oApogee will never be a reason a rocket recovers safely. Choose your motor delay as you would with no payload, and simulate with the payload mass included.

Lithium polymer batteries

The cell is the most dangerous object in the kit. Not because it is likely to hurt you, but because it is the only part whose failure mode is fire.

The rules

Never fly a damaged cell. If it is puffed, swollen, dented, punctured, or has been crushed, it is finished. Not "probably still fine". Finished.
A puncture can ignite minutes later, not instantly. If you damage a cell, do not put it back in a drawer and get on with the build. Take it outside, away from anything flammable, and watch it.
Charge on a hard non-flammable surface, in a LiPo-safe bag or a metal tin, and stay in the room. Charging unattended overnight is how the stories start.
Never short the terminals. The connector on these cells is small, the wires are thin, and a dropped pair of tweezers across the pads will do it. Keep unattached cells in their bag with the connector taped.
Use a cell with a protection circuit. Bare unprotected cells are sold and are cheaper. The protection board is the thing that disconnects the cell on over-discharge and short circuit, and this project assumes it is present.
Store at storage charge, not full. A cell kept at full charge for months degrades faster and is more likely to puff. Charge it the day before you fly.
Do not charge a cold cell, and do not charge a hot one. Let it come to room temperature first.
Dispose of it properly. Household waste is not proper. Most areas have a battery recycling drop-off, and hobby shops often take them.

Unverifiedstate the specific storage voltage per cell that oApogee recommends, sourced from the cell manufacturer's documentation rather than from hobby folklore, and state how to reach it with the hardware in this project.

What charging looks like on oApogee

Charging happens over the USB-C connector, with the cell attached. There is no separate charger to buy and no balance lead, because a single cell has nothing to balance.

Needs hardwaredescribe the LED behaviour during charge, at charge complete, and on a fault, once the hardware exists and that behaviour is implemented.

Flying with it

The cell flies inside the payload, which means it experiences boost acceleration and a landing impact. Secure it so it cannot move inside the pod, and route the wires so they cannot be pinched by the enclosure closing. A cell that shifts under boost and lands on a solder joint is a short circuit inside a sealed plastic box.

Inspect the cell after every hard landing.

Ground testing

The point of ground testing is that a payload which is going to fail should fail on your bench, where the consequence is an evening, rather than at apogee, where the consequence is the flight.

Do all four. In this order.

1. The bench dry run

Power the payload up and take it through every flight state without leaving the room. Arm it, simulate launch detection, let it run through to landing detect, and confirm that it produces a log file you can read.

Expected result: a complete log, on the flash, that exports to CSV and opens.

Needs hardwaredocument the exact procedure for simulating launch detection on the bench, including whether it is a firmware test mode or a physical motion, once the firmware exists.

2. The shake test

Hold the assembled payload, closed up in its pod, and shake it hard. Then listen.

Expected result: nothing rattles, nothing buzzes, nothing shifts. Anything you can hear moving is a component that will move under boost, where the acceleration is far higher than anything your arm can produce.

Open it up and check the cell is still where you put it.

3. The drop test

Drop the closed pod onto a hard floor from waist height, a few times, on different faces.

Expected result: it still boots, still logs, and the case has not opened. A crude approximation of landing, on purpose: a payload that cannot survive a clumsy drop will not survive a windy landing on hard ground.

Unverifiedonce hardware exists, establish whether the drop test is representative by instrumenting an actual landing and comparing peak accelerations. If a real landing is far harsher, say so and change the test.

4. The full arm-to-landing rehearsal

Do the complete flight day procedure at your desk. Charge it, fit it to the rocket, arm it exactly as you would on the pad, listen for the arm confirmation, wait as long as a real pad wait, and then take it through a flight.

Expected result: you discover the thing you forgot, at home, where it costs nothing.

The Preflight checklist page has the flight day version of this.

Stability is a safety issue

Adding mass to a rocket moves its centre of gravity, and a rocket whose centre of gravity has moved too far back is unstable. An unstable rocket does not fly badly, it flies sideways, into the ground, or into the flight line.

Re-simulate in OpenRocket with the payload mass and position included, before you fly it. Not after. Not on the second flight. A rocket that has flown well ten times tells you nothing about how it flies with a payload in a new place. Weigh your assembled payload and simulate with that figure.

The external pod makes this easier to get wrong than the sled, because it can be strapped anywhere and the obvious place is not always the right one.

The Mounting page carries the full treatment: which way the centre of gravity moves and why, the caliber margin to aim for, static ports, and the mass budget effect on apogee by motor class.

Radio

This section applies to oApogee Link and oApogee Track. If you are building Solo, there is no transmitter and none of this applies to you. That is one of the reasons Solo exists.

Part 15 and Part 97 are two different legal regimes and this page never mixes them. Read the one that applies to you.

The default: unlicensed operation in the US

oApogee Link and Track default to the 902 to 928 MHz band, operating under FCC Part 15. No licence is required and no callsign is needed.

Two obligations come with that. A Part 15 device must not cause harmful interference to licensed services, and must accept any interference it receives, including interference that stops it working. This band is busy, so that is a real consideration for a telemetry link rather than a formality.

The less obvious one is equipment authorisation. A radio module holding FCC modular approval has had the certification work done by its vendor. Designing your own RF section, or modifying an approved module's antenna arrangement, can move that responsibility to you. The Modules path recommends a pre-certified module specifically to keep this simple.

Primary source: 47 CFR Part 15

Unverifiedtranscribe the power and antenna limits for this band from the current text of Part 15 subpart C, with the section number. Separately, whether any provision restricts airborne operation of a Part 15 device here, answered either way: "nobody mentioned it" is not a finding.

Outside the US

The band changes and so do the rules. A 902 to 928 MHz module is not legal to operate in most of Europe.

For the EU and the UK, the equivalent short range device band is 863 to 870 MHz, which requires a different radio module because the matching network and antenna are tuned per band. It is not a firmware setting.

Unverifiedwhich sub-bands within 863 to 870 MHz are usable, the duty cycle limit on each, the relevant ETSI harmonised standard, the UK interface requirement document, and whether airborne use is permitted, which several national administrations restrict. Cite the primary documents. If the answer is that oApogee cannot be flown legally somewhere, the site says so.

If you are outside the US, the EU, and the UK, oApogee currently has nothing to tell you about your regulator and will not guess. Check with your national authority and with your local rocketry club, and please tell us what you find.

For licensed amateur radio operators

For people who already hold an amateur radio licence. If you do not, skip it: none of it is available to you, and operating under Part 97 unlicensed is a different category of problem from getting Part 15 wrong.

A licence buys considerably more transmit power and access to other bands, including the 70 cm and 2 m allocations, which opens up APRS as a tracking path with existing receiving infrastructure. For a long walkaway that is a genuine advantage over a private LoRa link.

It also brings obligations that a Part 15 user does not have:

Station identification. Your station must identify with your callsign at the intervals the rules require. A telemetry beacon that transmits for an entire flight and never identifies is not compliant. This has to be built into the firmware, not remembered on the day.
No encryption. Part 97 prohibits messages encoded for the purpose of obscuring their meaning. A telemetry format may be compact and binary, since that is efficiency rather than obfuscation, but it must be documented and decodable by anyone. This is one of the reasons the oApogee packet format is published as a specification.
Control operator responsibility. The licensee is responsible for the transmission, including one coming from a rocket that has left their immediate control.
Primary source: 47 CFR Part 97

Unverifiedstate the station identification interval and the specific rule sections for identification and for the encryption prohibition, transcribed from the current text. Then, separately, decide and document whether oApogee firmware will support a Part 97 mode at all in v1, because shipping a half-built compliance feature is worse than shipping none.

Rocketry rules

The safety codes

Most US club flying happens under the NAR Model Rocket Safety Code or the Tripoli equivalent, and your club will tell you which. Read the actual code rather than a summary of it, including this one.

A payload most often interacts with the limits on total liftoff weight, the requirement that the rocket be stable, and the rules on launch site dimensions and recovery. Adding one touches all three.

The federal rules

In the US, FAA regulations divide amateur rockets into classes. Class 1 is the model rocket class and carries the fewest requirements. Total vehicle weight is one of the criteria, which means adding a payload moves a rocket toward a class boundary. On a low power rocket with a payload in this mass range that is very unlikely to be the operative constraint, but it is worth knowing which direction you are moving in.

The full set of criteria is not listed here, and the omission is deliberate: a partial list of legal criteria reads like a complete one, and somebody would check their rocket against it and conclude they had finished. Read the primary source, or wait for the transcription below.

Primary source: 14 CFR Part 101

Unverifiedquote the Class 1 criteria from the current text of Part 101 Subpart C, with the section number and a retrieval date: the propellant mass limit, the total weight limit, and the construction requirements. Then where the boundary into Class 2 sits and what that entails.

Unverifiedconfirm whether a transmitter in the payload has any bearing on airspace notification requirements. The expected answer is no at Class 1, but expected is not verified.

Recovery

Fire

Dry grass and a hot motor casing are a real combination, and a field fire caused by a rocket flight is the sort of event that ends a club's access to a site permanently. Know the fire conditions on the day. If the field is dry and the wind is up, the answer is to not fly, and that answer is available to you.

The payload contributes a lithium cell to this picture. A cell that is damaged in a hard landing, in dry grass, is a worse outcome than a lost payload.

Permission

A rocket that lands on someone else's property does not give you permission to go and get it. Ask. If the answer is no, the answer is no.

Do not trespass to retrieve a payload. It is a cheap board and you can build another one. Standing crops in particular: walking into a field of wheat to find a small yellow box does real damage to someone's income, and it is why the pod is a bright colour and why the buzzer exists.

This is not a moral aside. Access to flying sites in this hobby depends almost entirely on landowners who tolerate rocketry, and that tolerance is spent by individuals one field at a time.

Livestock, roads, and people

Do not climb fences into pasture. Do not walk onto a road. Do not retrieve anything from a tree using a method you would not describe to somebody.

Before you use this page as authority

This page has been written carefully and has not been reviewed by anyone with formal expertise in the regulations it describes.

Where a claim matters legally or physically, the primary source is linked and it is what governs. Read it. If you find something here that is wrong, that is the most useful bug report this project can receive.