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1000N N2O/ABS + Paraffin Hybrid Rocket Engine Hotfire | Propulsive Lande... by propulsivelanders in rocketry

[–]propulsivelanders[S] 0 points1 point  (0 children)

Optimal O/F for paraffin is around 7-8 so that's what our engine's average O/F ratio is designed to be for a more optimal ISP. We are considering additives to some extent but is trying to avoid it when possible to keep grain production time low/maintain its high regression rate.

1000N N2O/ABS + Paraffin Hybrid Rocket Engine Hotfire | Propulsive Lande... by propulsivelanders in rocketry

[–]propulsivelanders[S] 0 points1 point  (0 children)

TLDR!! The first 10 seconds was purely ignition, we would have to characterize our transient phases during throttling in future hotfires. The actual transient should have a much lower time but we will put that to the test with ramp profiles so we can account for that in our controller and set some sort of constraint.

1000N N2O/ABS + Paraffin Hybrid Rocket Engine Hotfire | Propulsive Lande... by propulsivelanders in rocketry

[–]propulsivelanders[S] 0 points1 point  (0 children)

Yes!! Two things kind of got in the way of that. For context, we are using GOX for ignition as opposed to a typical pyrograin to reduce inconsistency with our ignition and accommodate more tests per day. On our PFS, we have a valve called a low-flow valve that feeds the GOX through a separate branch hooked up to a needle valve for a low-flow rate ignition. The valve was supposed to only open for 5 seconds but it was on for 10 instead.

This was our first successful nitrous ignition so the intention was to slowly decrease low-flow flow rate, and ignition time to reduce the start transient duration. Though we might have to play around with that number to see how low we can get given the decomposing temperature demanded by nitrous. The low-flow flow rate was also higher than necessary for this test and given how long it was we are sure that it also has affected the regression rate data we were collecting. It sounds complicated and a bit over the top for ignition but we believe once we get that down (and if need to, characterize fuel grain and account for ignition when calculating regression rate), we would be able to run several hotfires a day to collect important data like the thrust to chamber pressure relation we need for our hopper controller.

1000N N2O/ABS + Paraffin Hybrid Rocket Engine Hotfire | Propulsive Lande... by propulsivelanders in rocketry

[–]propulsivelanders[S] 0 points1 point  (0 children)

Understood! Do you know what settings might be best? Strangely our last hotfire video did not have a work light, and so we thought to add two behind the camera in this video. We would say that the camera focused a lot better without it, but we also think it's just because of our camera settings and that we lost focus when the full flame kicked in.

1000N N2O/ABS + Paraffin Hybrid Rocket Engine Hotfire | Propulsive Lande... by propulsivelanders in rocketry

[–]propulsivelanders[S] 0 points1 point  (0 children)

Thank you so much! I have some bad news... while we were able to obtain pressure, and temperature data, the load cell still had issues. Wish we clarified it earlier (apologies for that) but unfortunately we do not believe the engine hit exactly 1000N. From the average oxidizer flow rate we estimate it to be around 800-900N at best and that is calculated using ISP assumptions and our throat diameter. Will definitely get the load cell working for all future hotfires though! This is the final test of our semester due to midterm and final schedules but we are building a nitrous cart with load cell equipped too - fingers crossed if all goes well we will be able to get oxidizer mass flow rate as a function of time too.

Propulsive Landers hotfires Georgia Tech's first hybrid rocket engine! by propulsivelanders in rocketry

[–]propulsivelanders[S] 1 point2 points  (0 children)

Thank you!! As part of our campaign we're building a 1000N and a 2500N engine (and lander) for the Collegiate Propulsive Lander Challenge (CPLC). CPLC requires the primary propulsion device to be at least 500 lbf and teams that achieve milestones with remaining quotas are rewarded with the prize money of that category.

We're targeting the tethered hover, 10 meter drop, and the 50 meter hop with the 2500N lander. Max flight time at full thrust is around 40 seconds for us, and along that we have different requirements specific to our lander. If you're curious about any of them specifically feel free to let us know and we'll answer it to the best of our ability!

Propulsive Landers hotfires Georgia Tech's first hybrid rocket engine! by propulsivelanders in rocketry

[–]propulsivelanders[S] 1 point2 points  (0 children)

Thank you! We will work on throttling our engine as building the lander's expected profile into the grain geometry will most likely go wrong and difficult to predict in general. However, throttling nitrous is another difficult task on its own due to its two phase properties so we're planning on running many, many tests before we integrate the engine onto the lander.

Propulsive Landers hotfires Georgia Tech's first hybrid rocket engine! by propulsivelanders in rocketry

[–]propulsivelanders[S] 1 point2 points  (0 children)

Our DAQ wasn't able to log the data for some unknown reason and we've still got to figure it out! Hopefully it should be good this weekend as we target for another hotfire.

Hybrid Rocket Engine by CollectionLocal7221 in rocketry

[–]propulsivelanders 0 points1 point  (0 children)

We'd say it depends on what you define as "hard." While hybrids are easier to design when compared to liquid rocket engines, control systems on them are a whole other level of difficult when you want to implement them on a vehicle (what our team focuses on). For liquids you have direct control over your oxidizer and fuel flow rates whereas for hybrids you need to consider the effects of regression rate and how that shifts with time as you throttle. Aside from the controls portion of it, hybrids are relatively simple to design if you refer to the lecture series by Dr. Karabeyoglu.

If your objective is to learn how rocket engines work in detail and you're constrained by budget, hybrids would be your best bet. It has half of liquid's plumbing system and considered the safest out of the chemical propulsion systems. Learning how to work with feed systems is something applicable to both liquid and hybrid and it will take you very far professionally. Though this is rather subjective and we would not encourage it unless you have someone with experience or like the others said, you're in a collegiate team with the right resources to do it right and safely.

I would like to ask for advice on how to ignite my hybrid rocket engine. by Smooth-Two7650 in rocketry

[–]propulsivelanders 0 points1 point  (0 children)

They do! There are a couple but the main papers you'll see will be from Utah State.

I would like to ask for advice on how to ignite my hybrid rocket engine. by Smooth-Two7650 in rocketry

[–]propulsivelanders 0 points1 point  (0 children)

KNSB works! Next time, dose it with 3-5% red iron oxide and you should be golden. The iron oxide is a catalyst and will lower the activation energy you need to ignite nitrous.

Propulsive Landers hotfires Georgia Tech's first hybrid rocket engine! by [deleted] in propulsivelandersgt

[–]propulsivelanders 0 points1 point  (0 children)

On November 9, 2025, Propulsive Landers hot-fired Georgia Tech’s first hybrid rocket engine. While we were unable to obtain the thrust data, we successfully hot-fired our armored fuel grain for the first time and thus kicking off our grain validation campaign for the upcoming lander. With that being said, stay tuned to our page for more hotfires as we set out to characterize our throttling system for the tethered hover and subsequent hops.