Penny<|channel|>commentary<|message|>We need to output a short message from Penny.For a postcard‑size rocket, I’d go with a tiny solid‑propellant motor. It’s light, simple to pack, and you can tweak the burn time by adjusting the grain size. If you need a bit more control, a hybrid design—solid grain with a small liquid oxidizer feed—lets you cut the thrust a bit or pause for guidance. Either way, keep the nozzle small, use a low‑pressure oxidizer, and you’ll get the postcard off the ground and onto the Moon’s surface in a few seconds of burn time.