Student-Built Rocket Engine Packs A Punch

A group of students at Boston University recently made a successful test of a powerful rocket engine intended for 100km suborbital flights. Known as the Iron Lotus (although made out of mild steel rather than iron), this test allowed them to perfect the timing and perfect their engine design (also posted to Reddit) which they hope will eventually make them the first collegiate group to send a rocket to space.

Unlike solid rocket fuel designs, this engine is powered by liquid fuel which comes with a ton of challenges to overcome. It is a pressure-fed engine design which involves a pressurized unreactive gas forcing the propellants, in this case isopropanol and N2O, into the combustion chamber. The team used this design to produce 2,553 lb*ft of thrust during this test, which seems to be enough to make this a class P rocket motor. For scale, the highest class in use by amateurs is class S. Their test used mild steel rather than stainless to keep the costs down, but they plan to use a more durable material in the final product.

The Boston University Rocket Propulsion Group is an interesting student organization to keep an eye on. By any stretch of the imagination they are well on their way to getting their rocket design to fly into space. Be sure to check out their other projects as well, and if you’re into amateur rocketry in general there are a lot of interesting things you can do even with class A motors.

30 thoughts on “Student-Built Rocket Engine Packs A Punch

    1. Kind of curios myself…. In the past I have seen engines rated by force, apecific impulse for solid rocket and other fixed fuel availability engines, and so on…

      Force is generally lb (pounds force, sometimes lbf) or N (newtons). lb*ft is energy, and I don’t really know how that applies here, but, then again, I am not a rocket scientist.

      1. The Lotus-site says “The pressure-fed engine produces 2,500 lbs of thrust with 233 sec Isp SL” – so they use the ususal units. Perhaps they had the rocket on a horizontal foot long spar, measuring torque produced?

      2. My name’s Austin Briggs, and I’m the current director of BURPG. We’re well aware that thrust isn’t measured in torque! It appears as though the author of this article mistook our unit of “lbf” (pound-force) for “lb*ft” (pound feet). For reference, our 2,553 lbf of thrust is approximately equal to 11,356 N.

        Since the testing of this video, we’ve since designed a 450 lbf thrust engine powered by gaseous propellants to test critical propulsion technologies. We’re currently designing our most capable engine yet, stay tuned for updates on that. We’ll hopefully be out testing our Lotus Dev 2 engine (same as Iron Lotus above but with regenerative cooling) sometime in the spring.

    1. Yeah – this is a relatively old development. Unfortunately, it looks like the liquid-liquid development has quieted down lately in favor of more rapidly-accessible solids. It takes a LOT of work to keep a student group going in the face of 25+% turnover, especially when working on something as cumbersome as a liquid biprop design. We used to do HTPB-N20 hybrids, and even that was hugely tough to perpetuate despite being fundamentally much simpler.

      1. My name’s Austin Briggs, and I’m the current director of BURPG. We’re still kicking along. If you follow our Facebook, , we’ve been developing new propulsion systems and new vehicles. The time between tests can be pretty quiet when looking in from the outside, but we’re constantly working towards getting to 100 km. Currently designing our most capable engine yet. Stay tuned for us making it public.

  1. Each letter is in the range of 2x the thrust, literally starting with the Estes engines you played with as a kid. For reference, you can buy M engines off the shelf. Also, a lot of people have been moving to hybrid rocket engines even in M’s and below. There has been some back and forth with the BATF, and the last I knew, you could possess an M engine but without a proper magazine, you could not store an M engine. I have not been to a big launch in years, but back in the day, there were a lot of vendors that would either stock medium engine propellant grains (the casings on larger engines are re-usable) and would meet you there with pre ordered large engine grains. The hybrid rocket engines got around all of that.

  2. There is a huge difference between achieving a certain altitude as opposed to achieving orbit. An object in orbit not only needs to reach an altitude high enough to escape atmospheric drag, but also be traveling fast enough to escape gravitational pull, that’s over 17,000 mph.

  3. My first rocket engine at age ten ejected its nozzle never to be seen again. I learned from that to ask someone who knows what he’s doing to weld the thing in place (clearly brazing didn’t cut it). The second rocket engine suffered a bit of a malfunction that scared me sufficiently to not try to make my own rocket engines, and instead focused on playing with them computers. And I survived with no damage to any body parts.

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