Testing

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Testing

Once created, systems and subsystems will have to be carefully tested, checking for defects, design errors, model predictions, programming errors, and performance. In this page, we detail what will have to be tested for each subsystem, and how it can be done with a minimal cost.

Structure

Wings

Wings will have to sustain the mass of the rocket at accelerations from -2g to +4g. They will have to support heavy curving, and this can be tested by fixing the joint and putting a weight on the edge of wings. This weight will be calculated from the lift, mass and maximal acceleration that has to be endured.

Rocket body

Rocket body constraints are quite hard to calculate. Air pressure is the main problem, and happens in two ways:

  • on the fairing during normal operation due to speed,
  • on the body, when actuating the engine (or other) to modify pitch or yaw of the rocket. This force can be pretty intense when speed is mach3. Fortunately, launching from a plane will reduce air density drastically.

Joint between wings and body

The wings and the body have to be tightly coupled, to sustain the inertia of the heavy body. It also has to be simple enough to be separated for staging.

Mechanical systems

Plane actuators (for ailerons, elevators...)

We'll have to make sure the selected actuators conform to their specification, for the torque at least.

Fuel pumps

Fuel pumps are a critical part of the thrust system. If they don't provide a constant throughput, it's very likely that something will fail, especially for the rocket engine. Flow must not vary with accelerations of the liquid inside the tanks for example.

If a pressurization system is preferred over pumps for the rocket propellants, we'll have to make sure that there are no interruptions in the flow either, due to accelerations withstood.

Staging mechanism

The mechanism will have to be tested in full load operations, with strong accelerations (more weight). The staging sensor is a key element, because it will trigger the mission continuation, so we need to fully qualify it to know if staging could have occurred even if it did not detect it, or the opposite.

Fairing

A system with pre-tensioned springs should be the simplest option.

Orbital insertion

A simple orbital insertion mechanism is the releases of pre-tensioned springs, like what's used in Ariane rockets. However, they release the springs with a pyrotechnic system, and we'll have to find something less dangerous, costly and more easy to build.

Plane engines

Fans

Fans, and the fan shaft, will need to be carefully checked for balancing. This can be simply done with vibration sensing at various rotation speeds. Proper frequency of all the fans will thus be evaluated, allowing to model the behavior of all moving parts of the engine. It however does not allow to fully model the engine, because the frequencies may change because of the air displacement and pressure effects caused by the (core) shell of the engine. The final assembly can be checked in the same way than the blade, by checking vibrations at various rotation speeds.

A key element in turbine engines is the loose between the blades and the stator. They have to be really close one of each other for the engine performs efficiently. It means that the blades have to be exactly the same size (even if the manufacturing process of each blade is based on that, the assembly of a fan should be checked), and an abrasive crafting of the stator can be done. Revolving the rotor inside a soft material stator is a very simple and efficient process to ensure a minimal loose.

Physical property

Thrust, temperature. Long-term running validation (150% of available fuel at least).

Telemetry

The telemetry will only be able to work to these distances because there are no obstacles but the atmosphere. Therefore, testing it on real distance on the floor is mission impossible. The best way may be to measure up to how much attenuation the telemetry still works, and check if this is the expected attenuation of the atmosphere.

For tracking, tests should be made with a simple RC plane embedding our emitter. This will allow us to model the cone (or other shape) of reception with regards to optimal gain settings. It will also allow to check the ability to point the directive antenna to a (too quickly) moving object.

Rocket engine

TBD

Pre-prototype sensor validation

Some tests will have to be run before actually designing the whole system, in order to validate the use of a material, the capabilities of a particular part, or a design choice.

Most sensor validation will be done using a simple RC plane.

GPS

GPS tracking seems to be not accurate and not suitable for altitude sensing. This may be a limitation of the chips, because some satellites use GPS to position themselves, so it is not a system limitation.

Magnetometer

Embedding a 3-axis magnetometer on the plane will allow us to check if this information can be used and with what accuracy.