There is less than half a year before we aim to launch our space rocket HEAT2X/TDS80. HEAT2X is our LOX/Alcohol bi-liquid launch vehicle and TDS80 a scaled down capsule representing the same geometry as our full scale capsule Tycho Deep Space II.

All teams are working hard and dedicated on various subsystems and I this is a follow up blog on the ballute system which are being developed at the moments. Thanks to all the readers who emailed me links to Nomex suppliers. There is a batch of bright orange (very important aesthetic factor) on its way to Copenhagen.

Some very cool developments and experiments are happening soon related to the drag systems which will are supposed to provide a controlled re-entry system for the capsule. If our 83 kg scaled down capsule, made from aluminum, is supposed to survive the descent there are certain steps that has to work and they are:

Top lid jettison

When the capsule reaches apogee the top lid, also being the tip of the rocket, has to be jettisoned in order to deploy the first drag-device – the ballute. The top lid jettison is done by creating a lot of pressure inside the chamber which bends aluminum sheets holding the lid in place.

Ballute deployment

After top lid jettison the ballute is being deployed mechanically and has to obtain is drop-like shape immediately. The shape is normally create by gas-pressure but we intend to create this by adding an interior mechanically systems based on a self-shaped Hello Kitty tent. I have kids and have often come across small tents which can unfold themselves just by unpacking. They have inner wire structures creating the shape and this may be a good passive solution.

The ballute must preserve its shape using air inlet openings providing a constant internal pressure from the low pressure (but high speed) surroundings. The ballute is working as active drag device from 100 km to 3 km during speed of app 0 – 4000 km/h and has to be placed app 10 meters above the capsule. Eventually the ballute will pull the drogue releasing a 3-ring system.

Drogue deployment

A drogue is normally used as the initial aero breaking before deploying the main parachutes. However, this scaled capsule only has a mass of 83 kg and does not require “main parachutes”. The drogue which will provide the final drag should be enough to ensure a splash down at app. 40 km/h – same as for the full scaled capsule using three main parachutes.

The drogue is pulled by releasing the ballute (by a 3-ring system) in descent velocities below 400 km/h. It has a pilot chute deployed by a spring eventually deploying the main drogue. I have not spend time designing or producing a drogue - I simply bought a drag-racing chute on the internet.

The ballute and drogue are both fixed in each two points by the top flange of the capsule. This is required to have a symmetric pull of both the ballute and drogue for correct aerodynamic re-entry and splashdown.

TK Fix points for ballute and drogue. Image: Kristian von Bengtson

The capsule splashdown is followed by the inflation of a 95 liters uprighting divers buoy. The capsule is not pressurized and will sink fast if not attached this floater. Even though all data is being beamed back to Earth we really like to have this piece of test hardware for future studies and bragging.

Capsule TDS80 interior chute chamber sketch with parts related to descent scenario. Image: Kristian von Bengtson

One of the interesting experiments to be performed very soon is top lid jettison by creating instant over pressure. As explained earlier we are not able to use nitrocellulose for this in a vacuum environment. The next step is testing an airbag gas charger – however, we are not certain this will work as well due to vacuum dispersion in the ignition charger.

This week I have constructed two top lids (expecting to destroy one during testing) for this experiment. The top lid is fastened to the top chute chamber flange by four bolts with aluminum sheets in between which will be deformed during the air bag pressure overload.

Capsule top lid production. One for testing and one for flying into space. Image: Kristian von Bengtson

For the experiment we simply have to add the lid onto the capsule top flange and suck all air out of the chute chamber which is packed with towels (mimicking chutes). By creating a near-vacuum in the chamber we are able to identify if there is any issues with using the air bag system like we saw with nitrocellulose. Then we power up the air bag system and blow off the hatch. In some way we need to protect both the surrounding and the top lid which may leave the area – never to be found. I think we will have lay down the capsule and blow the top lid into some kind of soft packing - like housing insulation material.

Søren prototyping ballutes. Image: Søren Gregersen

So, tomorrow the Nomex will arrive and Søren will continue the ballute production. He is working basic paper prototypes to get a sense of shape and size.

The top lid experiment will happen as soon as I get a foam silicone packing to keep a tight sealing between top lid and lower capsule part. About time – I love blowing stuff up…

Don't hesitate to comment if you have concerns, good ideas or suggestions.

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Kristian von Bengtson