SPL and others such as XCOR have built regenerative engines using separate chamber, throat saddle, and outer jacket (CSJ-design). This engine uses exactly this design. The outer jacket is shown in the left picture on the left only. The jacket does not constrain the chamber’s thermal expansion during firing. Thus the thermal strain, plastic yield and cracking cycle never get started. In our engines we haven't seen any distortion, yielding, or cracking. This construction contributes to long life by making it feasible to disassemble the engine for inspecting and removing coking deposits if needed. We think this CSJ approach is good for thrust levels up to 100 kN and beyond. The mass of the engine is ~5 kg. It operates with alcohol/LOX or kerosene/LOX at a chamber pressure of 25 bar (362 PSI) and is restartable.

Parts of the combustion chamber. The chamber is designed to be fully demountable to test various configurations. This is also important to inspect the liner and its cooling channels after test runs. Click on the image to enlarge...	The inner liner with the milled cooling channels. One of the two halves of the throat closeout has been removed. The closeout mates very precisely with the liner to prevent any bypass flow in the throat area. The temperatures in the cooling channels are measured by thermocouples of 0.5mm diameter that are mounted through small openings in the outer shell and in the closeout. Click on the image to enlarge ...
Ignition! The picture shows a test run under rel. low chamber pressure (o.6 MPa) using LOX/ethanol at an O/F of 1.3. In this test, the injector was equipped with only 3 injector elements.	An overview of the test setup. One can clearly see the frozen LOX line and LOX valve, the 2.5 kN chamber with its feeding lines, the torch igniter and several thermocouples. The LOX tank is on the top left. The picture below shows a modified 2.5 kN engine at full throttle

This 10kN (2.3 klbs) engine operates with Kerosene/LOX or Alcohol/LOX and is also restartable. The injector can be fitted with an ablative combustion chamber, a CSJ-chamber or with a dual pass copper chamber surrounded with electro plated nickel. Chamber pressure is 25 bar (362 PSI)

The SLR10k-I injector fitted with a mockup chamber. The chamber diameter is 140mm, throat is 56 mm. Nozzle is a 80% bell with an expansion ratio of 1:5.6. Weight is about 7 Kg. It is equipped with the complete injector plate, kerosene supply (movable in two orthogonal axes) and the spherical LOX joint.

The combustion chamber consists of an inner copper liner with machined cooling channels and an outer shell of electro plated nickel. The picture shows a detail of a sample cutted out of the electro plated combustion chamber wall. This design is very light-weight and handles very high heat transfer densities. The same principle is used in the SSME and the Vulcain. This design is subject to fatigue deformations and the cooling channels are difficult to inspect. For reusability we suggest our CSJ approach.

We have various engines suitable for attitude or reaction control. This systems have been tested with GOX (gaseous oxygen), LOX (liquid oxygen), nitrous oxide N₂O as the oxidizer and various hydrocarbons like ethanol (and other alcohols), kerosene, propane, butane and ethane. We have also tested RCS engines based on catalytically decomposed N₂O and H₂O₂. The thrust level of these engines is in the range of 1-200 N. These engines can also act as igniters for bigger engines.

A RCS running on kerosene/GOX. Thrust 50N	200 N thrust with ethanol/GOX

SPL has lots of experience with solid propellants. In the SSR12k-I "Tethis" booster on the picture below we tested fast burning mixtures based on HTPB/Al/AP and Catocene respectively Butacene as very effective burning rate modifiers. SPL has test equipment to characterize new propellants under various conditions. Propellants are beeing processed remotely by a ABB-robot. Have also a look at our igniters.

The SSR12k-I "Tethis" booster. The nozzle contains a throat made of high density graphite. This is a heavy walled test setting, not flight hardware.	Under full thrust of 12'000 N.

SPL and its partners developed several versions of hot water (steam) boosters. They have been used as JATO boosters. Hot water rockets are cheap to operate and environment-friendly and therefore perfect to accelerate dollies, sledges for various applications or applying high forces to structures like bridges for a short duration. We can design and build devices with thrust levels of up to 50 metric tons (110 k lbs).

The SHWR1.2k-I mounted on the test stand. In front one can see the regulator for the 3 x3 kW heating cartridges. Close to the nozzle one can see the security valves and the pilot valve for the nozzle's internal valve.	Hot water rocket engines are safe devices. All engines are certified by the national authorities.

Our torch igniters operate with gaseous oxygen and ethane, propane or hydrogen. We use them on all of our engines and gas generators (for turbo pumps). They made it through thousands of ignition sequences without failure. Feeding pressure is up to 40 bar (580 PSI) or up to 60 bar (670 PSI) with H₂/O₂. Diameter of the body is 40mm and the mass is ~300 grams (without valves, plumbing and high tension source). If you prefer liquid propellants for the igniters, then just have a look at our RCS engines. We also made successful tests with catalytically ignited H₂/O₂ devices (no spark or glow plug needed) and resonance igniters (so-called Hartmann-Sprenger tubes).

The torch igniter fires through the injector plate of modular 2.5 kN LOX/HC engine. On the left: the attached copper case of the torch igniter with the spark plug.	The same type of igniter running on ethane/GOX

We developed two types of pyrogen igniters for the solid propellant motors. The SPI-MagTef bases on sintered Magnesium/PTFE as made in a special process developed by SPL. This igniter is a solid single piece, mechanical rugged and insensitive to humidity (it even works submerged in water). The SPI-I is a classical pyrogen design working like a small solid rocket motor and can also be used as an igniter for liquid propellant engines. Both have been tested in the SSR12k-I "Tethis" motor. We also tested basket igniters based on Mg/PTFE- and Boron/KNO₃-pellets.

This Mg/PTFE igniter brought the "Tethis" motor to full thrust level of 12 kN within 30 ms without any pressure peaks	The SPI-I uses a silica-phenolic housing containing a casted fast burning HTPB/AP grain

A cut-away view of the SPI-I

To test and characterize engines, fuels etc. a thrust test stand is essential. With this test stand both liquid engines as well as solid propellant motors with thrust up to 100 kN (10 tons) can be tested.  The measuring table is mounted on 8 hysteresis free "Flex"-joints (with integrated safety stop extensions). The table is made of aluminum and has many integrated "T" grooves for easy mounting of different kind of engines, valves and other equipment. The test bench is bolted to a concrete block which is in turn connected to a 30 tons foundation plate. The total mass of the test stand cell and the sound absorbing tunnel amounts to more than 100 tons! The load cells can be exchanged to the respective measuring range.  The current development status permits testing engines with a thrust of up to 30 kN. By prolongation of the sound absorbing tunnel and a slight upgrade of the test bench the range can be enlarged to approx. 120 kN.

The orange container houses the sound absorbing device. The grey container with the fan is the actual test cell. In the background the control room which contains the data acquisition.
The muffler with extracted extension tube. Muffler and extension tube can be cooled with water injection which also suppresses the noise emission	The rocket engine to be tested is built up on the table of the test bench. It fires into an extension tubus of the absorber tunnel.
The control room. All operations can be controlled remotely. Many video cameras are monitoring and every detail in the test cell and the surroundings of the test facility. Multi-channel high-speed DAQ is used.	Design studies and proposals for test stands designed for thrust up to 300 kN have been made for ESA and NASA

With the high pressure injection chamber we are able to analyze the behavior of rocket injection systems in a high-pressure environment (cold spray tests). So we can investigate the size, speed and distribution of the droplets injected into the chamber. The system allows the analysis of the behavior of various injectors (doublets and triplets) and their injection patterns. The chamber can handle pressures up to 60 bars.

	The picture shows a spray pattern enlightened by the laser beam of the laser-doppler anemometer made by DANTEC which is one of the leading manufacturer of instruments for flow and particle measurements. The orifices of the doublet have a diameter of 0.8 mm, the chamber pressure is 20 bar and the differential pressure over the injector is 10 bar. Click the picture to enlarge	The chamber is designed for working pressures up to 60 bar. The spray patterns can be observed through four windows. This allows also investigations with a laser-doppler anemometer to measure size, speed and distribution of the droplets.

• Gas transfer and mixing facilities
  We can mix and transfer any gas from any pressure level (up to 1000 bar) to any pressure level (up to 1000 bar). This is very useful when preparing Tridyne gas mixtures.
  
• Vacuum chamber with a volume of 24 m³ for altitude testing.
• High Pressure Test Equipment, hydro testing up to 1000 bar

During expansion of the pressurization gas into the propellant tanks it cools down and looses a lot of its specific volume, this means one needs even more pressurization gas. Tridyne uses a low percentage oxygen/hydrogen mixed in Helium or Nitrogen which is reacted in a catalyst to heat it up and so the volume increases. The percentage of the O2/H2 in the Helium is so low that it cannot be ignited under normal conditions. So it is possible to store the whole mix in one tank without any danger. Not only will the outgoing gas be heated, but also the remaining gas in the Helium Tank. The catalyst consists of precious metal coated ceramic pellets with a very high internal surface of  >200 m²/gramm. Hot gas produced by a Tridyne device can also be used to drive turbines or piston engines used for propellant pumping or APU applications. We also hold a patent for a pressurization system using Tridyne. Here is a brief description of the patent. The pressurization system of the Australian AUSROC 2.5 rocket uses a Tridyne Device from SPL.

A catalytic test device with an inner diameter of 20 mm and a bed length of 100 mm. They are made of a stainless steel alloy and have provisions for the mounting of thermocouples and pressure measurements.	Graph of the temperature response in the outlet gas stream

• Pressure regulators
• Cryogen Particle Filters

• Consulting/Engineering
  We have done several design studies for various companies and organizations. The example below is a proposal for a low thrust, long burn time (and therefore regeneratively cooled) cruising propulsion system:
  
• CAD/CAE/CFD
  We work with state of the art CAD/CAE. CFD (incompressible, compressible flow up to mach 5) can be done via our university partners, including wind tunnel tests.