Delay Grain

Delay Grain is a flight book and fleet register for hobby model rocketeers — Estes kits on a school field, club launches with NAR, UKRA, CAR or AMRS sections, or scratch builds on small certified motors anywhere from the Netherlands to Colombia.

Open it at the launch table between flights. Pick a rocket, pick a motor out of your own motor box by its real code — C6-5, B6-4, D12-0 — and Delay Grain reads it for you: total-impulse class, average thrust, delay in seconds, booster suffix. It shows the liftoff mass with that motor fitted and the thrust-to-weight ratio next to the familiar 5:1 rule of thumb, as a note, never a verdict.

Once the flight is over, log the outcome in two taps: altitude, ejection timing (early, at apogee or late), recovery condition and how far you walked to get it back. Delay Grain remembers. Fly a rocket on the same motor family a few times and it starts to notice a pattern — Bullpup on C6: last three ejections late, try C6-3 — so the next flight gets a better guess instead of a repeat mistake.

The motor box counts your stock down after every flight and flags codes at your reorder point before the next hobby-shop order. The Fleet tab keeps a photo, dimensions, recovery gear and a full repair log for every rocket, even the retired ones. The Log tab filters every flight by rocket or motor, charts altitude per rocket/motor pair, and turns twelve small milestones into patches worth chasing.

Six starter rockets, a stocked starter motor box and one sample session mean the app is never empty on first launch — no account, no onboarding carousel, straight onto today's pad.

Delay Grain does not simulate flights, does not calculate stability or centre of pressure (OpenRocket already does that job well), and does not show launch-site maps. It never claims a flight or a field is permitted under any regulation — it shows your own pre-flight checklist, not legal advice.

Everything stays on your phone. No account, no login, no network calls, no ads, nothing to buy.