Cryogenic Rocket Propulsion
Solid rocket motors have historically been DARE’s preferred engine choice due to their simplicity and ease of manufacturing. This type of engine has propelled Stratos to an altitude of 12.5 km, setting the European amateur rocket altitude record. In 2015, Stratos II+ reached an altitude of 21.5 km with the use of a hybrid engine, again breaking the altitude record. The goal of DARE remains to launch rockets reaching a higher altitude, and eventually to be the first student team to reach space at 100 km. With the next rocket, Stratos III, DARE is working hard to reach this goal. But in order to reach even further, more powerful rocket motors will be required.
Recently, a group of DARE students decided to look beyond the 100 km goal. In the Autumn of 2015, the Cryogenics Project was founded with as mission to develop new technologies that could bring DARE to 150 km and beyond. The team will attempt to build a rocket engine that utilizes more powerful propellants. Analysis showed that a combination of cryogenic liquid oxygen and bio-ethanol propellants could take us to these altitudes. On this page, we would like to tell you what we will be doing during the upcoming academic year.
Hot-fire test of small-scale engine
The goal we set ourselves is ambitious: the engine we want to develop will have to produce a thrust of around 10 kN, enough to lift a small car off the ground. It is challenging to get this right on the first try, hence a set of milestones has been carefully selected to lead the team through this development. The goal of the first year is to produce an engine capable of producing a thrust of 1.5 kN, using liquid oxygen and “green” bio-ethanol as its propellants. This smaller engine will help us verify certain engineering design choices and serve as a testbed to demonstrate reliable performance. If this proves to be successful, a larger scale engine will be built.
The main goals set for this year’s project are:
- Construct a feed system capable of handling liquid oxygen (LOX) at a temperature of -170° Celsius at 60 bar;
- Have a rocket engine that can sustain stable combustion of the LOX and bio-ethanol propellant combination with a temperature of 3500° Celsius at 15 bar;
- Develop a reliable ignition source based on a spark torch ignitor design;
- Design an effective, easy-to-produce injector, capable of being scaled up for a 10 kN engine;
- Use an automated control sequence for valve actuation.
The road to the hot-fire test consists of yet smaller milestones, in which we will design and test individual subsystems. After achieving their own requirements, they will be integrated into the 1.5 kN engine which will then be put through a series of testing.
The first major test campaign is already almost complete: liquid nitrogen (LN2) testing of a sample feed system and injector. In this section, you can find our testing plans.
Cold-flow tank pressurisation test
These tests consisted of filling and pressurizing a DARE fabricated LOX storage tank, and then emptying this tank again through a set of feed lines and valves. These tests gave the team its first experience with the handling of substances at cryogenic temperatures. Certain parameters were monitored with sensors. This data will be compared with the predictions of the theoretical models that were developed by team members to predict physical behavior. Liquid nitrogen instead of liquid oxygen was used, as it is physically very similar, but with the advantage of being less reactive, hence allowing for safer testing which can be conducted on the TU Delft campus.
Cold-flow injector test
The next test in the series will be the cold-flow injector test. For this test, the propellant storage tanks will be connected to a complete feed system, ending at the injector. During these tests, extensive data can be gathered about pressure drops over our components and the state of the flow in our system up until the injector. It will give the team experience on how to properly assemble the system to avoid leakage. In addition, the control system for valve actuation can be tested.
In parallel to the progress of the first two tests, the spark torch ignitor system will be developed and tested. The main goal is to obtain a highly reliable ignitor. This is a main goal for the team as there will be only a limited number of opportunities to test a complete assembly of our engine or to launch a rocket. If the ignition of the rocket engine fails, a complete test or launch campaign can be delayed. As these campaigns are often conducted at remote locations, the ability to postpone is often very limited.
Integration and hot-fire tests
After successful testing of the subsystems, the cryogenics team will move on to the last milestone. A fully assembled engine will be readied for testing. On a dedicated test site with sufficient safety precautions and features, we can test our cryogenic rocket engine with the LOX and bio-ethanol propellants. During these tests, we can measure many important performance parameters such as the thrust level, thermal data of the combustion chamber, combustion stability and more.
ERIKS is an international industrial service provider offering a wide range of high-quality mechanical engineering components and associated technical and logistics services. ERIKS is helping DARE in the development of the cryogenic rocket engine feed system.
Air Liquide is a French multinational company that supplies industrial gases to a variety of industries. Air Liquide is supporting the cryogenics project by supplying a dewar flask for the storage of LOX and also a supply of LOX.
Advanced Lightweight Engineering Delft is a company that specializes in the design, development and production of lightweight structures. ALE supports DARE by giving lightweight design and simulation advice and additionally is providing a testing facility for the Cryogenics team’s cold-flow tank pressurization test.