A-Class motor altitude record
How high can a A-motor go? Design light and find a way to beat the previous winner or the starting altitude to win. Win more each time you beat the previous entry too as it's going to get harder!
About this challenge
An A motor gives you no more than 2.5 Ns of total impulse, so every gram and every bit of drag counts. This challenge is simple: fly the highest model rocket you can on an A motor, logged with an Altimeter Cloud altimeter.
The first flight to reach 160 m wins. After that, every flight that beats the last winning height by 12% wins again, so the bar keeps climbing. For comparison, the UKRA single motor A class record stands at 214 m (703 ft).
Which motors count as an A?
Any motor with 1.26 to 2.5 Ns of total rated impulse. That covers the 18 mm Estes A8-3 and the 13 mm A10-3T and A3-4T. The class goes by the total for the whole flight, so two A motors in a cluster make a B and won't count.
Tips for flying high on an A
- Go small and light. A minimum diameter rocket built around a 13 mm motor has far less drag than a typical 18 mm kit.
- Keep the finish smooth, with a pointed or ogive nose cone and thin, sanded fins.
- Pick a delay that fires near apogee. Too early costs you height; too late and the rocket is coming down fast when the recovery opens.
- Use a streamer rather than a big parachute, so it comes down near the pad.
- Fly on a calm day, straight up. Wind tips the rocket over and every degree off vertical costs height.
- The altimeter is part of the weight. Weigh the rocket ready to fly and enter the lift-off weight on the flight page.
Entering your flight
Upload the flight as normal, then on its flight page add the motor and the lift-off weight, and set the launch site, date and time. Then open the Add my flight tab here and pick it. Your altimeter's accelerometer measures the burn, which proves the motor really was an A.
Heights are corrected for the day's weather, so a cold day doesn't give anyone a head start.
Fly safely, and follow the safety code of your club or national association.
Your altimeter works out height from air pressure using a standard atmosphere: the sea-level pressure and temperature in its settings, usually 1013.25 hPa and 15 °C. The real day is rarely standard. Cold air is denser, so an altimeter set for 15 °C reads high on a cold day and low on a warm one, by roughly 1% for every 3 °C, which is about 2 m at 200 m.
So every flight is judged on the height it really reached, we take the weather added to your flight for its launch site, date and time, and recalculate the whole log with it. It's the same adjusted apogee the flight page shows, and it's the one that scores.
How it pays
- First win
- Reach 160.0 m
- After that
- Beat the last winning result by 12%
- Your own result
- Beating it pays again
- Points paid
- Once we have checked the entry
- Dates
- From 5 Nov 2026
Required altimeters
The flight is checked against the altimeter that recorded it
- Hardware
- Rev 4 or later
- Firmware
- 1.65 or later
- Hardware
- Rev 1 or later
- Firmware
- 2.50 or later
- Hardware
- Any revision
- Firmware
- 1.02 or later
- Hardware
- Any revision
- Firmware
- 1.00 or later
Required flight details
Everything is checked when you add a flight- Your own flightFrom an altimeter on your account, and a real flight rather than a test.
- A A motorAdded on the flight page. The class is the total rated impulse of the flight's motors: A is 1.26 to 2.5 Ns.
- Single motorOne motor on the whole flight: no cluster and no staging.
- Single stageCounted from the stages of the motors added on the flight page.
- Motor proven by its burnThe total impulse measured from the altimeter's accelerometer and the lift-off weight has to be within 20% of the rated motor, as NFPA 1125 allows.
- Lift-off weightEntered on the flight page.
- Launch siteSet on the flight page.
- Launch date and timeSet on the flight page.
- Launch weatherAdded to the flight once its site, date and time are set. Altitudes here are corrected for it.
- Flown during the challengeOn or after 5 Nov 2026.
Your altimeter works out height from air pressure using a standard atmosphere: the sea-level pressure and temperature in its settings, usually 1013.25 hPa and 15 °C. The real day is rarely standard. Cold air is denser, so an altimeter set for 15 °C reads high on a cold day and low on a warm one, by roughly 1% for every 3 °C, which is about 2 m at 200 m.
So every flight is judged on the height it really reached, we take the weather added to your flight for its launch site, date and time, and recalculate the whole log with it. It's the same adjusted apogee the flight page shows, and it's the one that scores.