# What if you made a jetpack using rifles? Source: https://www.youtube.com/watch?v=IdlQsjq5vKo Recap page: https://rapidrecap.app/video/IdlQsjq5vKo Generated: 2026-02-10T20:05:58.119+00:00 --- ## Quick Overview Building a jetpack out of downward-firing rifles is theoretically possible, requiring over 300 rifles firing continuously for 150 rounds each to generate enough thrust (around 150 lbs) to lift a 10-pound object plus the rifle itself, but the fuel/ammunition mass and the immense recoil force (up to 30 Gs) make it impractical and lethal. **Key Points:** - A 10-pound rifle firing 10 rounds per second of 10-gram bullets at 700 m/s produces approximately 15 pounds of thrust, resulting in a thrust-to-weight ratio of 1.5, which is just enough to lift itself off the ground. - To lift a 60kg (132 lb) rider, the calculation suggests needing over 300 rifles, each loaded with 150 rounds, firing continuously for 150 seconds to achieve a thrust-to-weight ratio greater than 1. - The GSh-6-30 autocannon, which weighs half as much as the GAU-8 Avenger but has a higher rate of fire, produces a thrust-to-weight ratio of 30 when fired downward, offering extreme but unsustainable lift. - Firing the GSh-6-30 generates an acceleration force of 30 Gs on the operator, which is lethal, and its massive recoil (about 5.5 tonnes) is enough to damage the aircraft it is mounted on. - The main limiting factor for a rifle-jetpack is ammunition mass; carrying enough ammunition (over 150 rounds per 10-pound rifle) adds too much dead weight, eventually making the device too heavy to take off. - Theoretically, if the ammunition weight could be ignored, a rifle jetpack could reach an altitude of about 200 meters before running out of ammo. ![Screenshot at 0:07: The initial premise question is displayed: "Q. Is it possible to build a jetpack using downward firing rifles?", setting up the entire physical calculation.](https://ss.rapidrecap.app/screens/IdlQsjq5vKo/00-00-07.jpg) **Context:** This video explores the feasibility of building a personal jetpack using multiple downward-firing rifles, based on the principles of thrust derived from Newton's Third Law. It uses stick-figure animations and physics calculations, referencing concepts like the thrust-to-weight ratio seen in rocketry (like the Saturn V) to analyze the required number of rifles and the practical limitations imposed by ammunition weight and recoil. ## Detailed Analysis The video investigates whether a jetpack can be constructed using downward-firing rifles based on Newton's Third Law. The initial calculation uses a hypothetical 10-pound rifle firing 10 rounds per second, each weighing 10 grams at 700 m/s, which generates about 15 pounds of thrust, resulting in a thrust-to-weight ratio of 1.5, enough to hover the rifle itself. However, for a 60kg rider, this requires over 300 rifles firing continuously for 150 seconds each to achieve liftoff (thrust-to-weight ratio > 1). The analysis then shifts to real-world powerful weapons, noting the GAU-8 Avenger (5 tons recoil) and the even more powerful Gryazev-Shipunov GSh-6-30, which has a thrust-to-weight ratio of 30. While the GSh-6-30 setup could achieve a vertical acceleration of 0.5 Gs with a rider, the recoil causes 30 Gs of acceleration on the operator, and firing more than 30 rounds causes overheating. The ultimate limiting factor is the mass of the ammunition; carrying enough bullets (e.g., over 150 rounds per rifle) adds too much dead weight, making the entire assembly too heavy to ever leave the ground, despite the theoretical thrust capability. ### Recoil and Thrust Calculation - Firing a 10lb rifle at 10 rounds/sec (10g/bullet at 700 m/s) yields ~15 lbs of thrust, for a T/W ratio of 1.5 - A single rifle can lift itself off the ground, but not a rider. ### Scaling to Lift a Person - Lifting a 60kg rider requires over 300 rifles, each needing 150 rounds of ammunition, leading to massive fuel/ammo weight. ### Analysis of Powerful Cannons - The GSh-6-30 autocannon offers a thrust-to-weight ratio of 30, capable of lifting the platform plus rider, but the recoil imposes 30 Gs on the operator, which is lethal. ### The Ammunition Weight Problem - Carrying enough ammunition (e.g., >150 rounds per rifle) adds significant dead weight, quickly reducing the overall thrust-to-weight ratio below 1, preventing sustained flight. ### Final Outcome - While theoretically possible to lift off with sufficient rifles (>300), the need to carry the fuel/ammo makes the weight prohibitive, and the recoil/heat issues are fatal. ![Screenshot at 0:14: Illustration showing that firing a rifle downward generates recoil pushing the user upward, illustrating the basic principle of the jetpack.](https://ss.rapidrecap.app/screens/IdlQsjq5vKo/00-00-14.jpg) ![Screenshot at 0:38: Comparison showing that a rocket needs a Thrust/Weight ratio greater than 1 \(like the Saturn V's 1.5\) to take off, establishing the required performance metric.](https://ss.rapidrecap.app/screens/IdlQsjq5vKo/00-00-38.jpg) ![Screenshot at 1:07: Calculation showing that a 10lb rifle firing 10 rounds/second generates approximately 15 lbs of force \(thrust\), exceeding its 10 lbs weight by 50%.](https://ss.rapidrecap.app/screens/IdlQsjq5vKo/00-01-07.jpg) ![Screenshot at 2:11: The graph illustrating that the Thrust-to-Weight Ratio increases non-linearly with the number of rifles, plateauing around 1.5 \(or 0.5 Gs acceleration\) for the rider due to diminishing returns from added mass.](https://ss.rapidrecap.app/screens/IdlQsjq5vKo/00-02-11.jpg) ![Screenshot at 3:37: A humorous depiction of the operator being pulled backward by the recoil of the GAU-8 Avenger mounted on a car, illustrating the massive backward force generated.](https://ss.rapidrecap.app/screens/IdlQsjq5vKo/00-03-37.jpg)