Vehicle

The VESA “Gauchito” is a conventional style rocket launch vehicle, using 4 hybrid rocket engines in cluster configuration.
The length of the “Gauchito” is 12 meters without the escape tower, with a diameter of 2.20 meters in the main body, and 6.60 meters including the aerodynamic fins. The weight of the rocket is 8,000 kilograms while the empty weight is 2,400 kilograms.

The capsule can accommodate 3 crewmembers with a maximum weight of 300 kilograms. The capsule maintains a controlled atmosphere of oxygen and nitrogen and the crew will use full pressure suits with 100%.oxygen

Propulsion

The propulsion system of the “Gauchito” was designed by Prof. Jorge Lassig. Its combines safety, economy, and reusability.
The propellant grain, shaped as a cylinder and using several channels with geometrical shapes is placed in the combustion chamber.

Esquema de un motor cohete híbrido

Combustion

The combustion is produced in the grain channels. Thanks to the heat freed by the chemical reaction, part of that heat is transferred to the grain, and being “ablationed” more propellant is bought into the combustion.
Once the combustion starts, part of the heat generated is transferred from the flame to the solid, by radiation, conduction and convection.

The limit layer governs a great part of the ablation process in the solid, so the rate of radius growth of the channel depends on the amount of gases circulating by it.
In this manner, the combustion can be controlled by the amount of oxidizer injected in the combustion chamber.


Advantages of the Hybrid Motors.

On of the major advantages of an hybrid rocket engine is its safety. The risks of explosions is almost inexistent since a crack in the grain do not follows an immediate explosion, as happens in the solid rocket engines. This is due the fact that the reaction is governed by the amount of oxidizer entering to the combustion chamber. Other advantage of the hybrids is that they can be restarted several times and in a very easy way compared to liquid rocket engines. Also the thrust can be regulated by the amount of oxidizer entering to the chamber. The risk of overpressure is easily regulated by a overpressure valve which turn off or reduces the amount of oxidizer entering to the chamber. The specific impulse of the hybrids (Isp) are from 210 to 270 seconds being of intermediate impulse between the solids and liquids.

Foto muestra un prototipo en escala de motor cohete híbrido. Dicho motor funciona con Resina Poliéster como combustible, y Oxígeno como oxidante

Characteristics

The “Gauchito” uses 4 hybrid rocket engines which burns Polyester Resin as propellant, and liquid oxygen (LOX) as oxidizer for 60 seconds. The throttle can be regulated and the engines are re-startable. The propulsion system has redundant safety devices and can be stopped in case of malfunction. The total thrust is 250,000 newtons (52,910 lb).
Each engine uses 380 kilograms of polyester resin and 1,080 kilograms of LOX. This requires a volume of 4 m3 for the 4 rocket engines. The LOX is feed by high pressure nitrogen coming from an additional tank located at the top of the rocket body.

El dibujo da una idea de la configuración de los motores del “gauchito”

The total length of the rocket body is almost 8 meters, with a 2 meters diameter.
The pressurized nitrogen tank is ½ meter diameter and the spherical LOX tank is 2 meters diameter.
The longitude of each motor tube is 3,3 meters with a diameter of .60 meter.

Reentry

The reentry of “Gauchito” is very similar to the Apollo spacecraft of the United States. We have chosen this vehicle since there is enough technical information about this system from public sources.
Different from the Space Shuttle, a ballistic capsule survives reentry thanks to a thermal shield that maintains the interior temperature of the capsule to design specifications.

Recovery

The recovery of “Gauchito” will be made by conventional cargo parachutes. First a drogue parachute will open to stabilize and initially reduce descent speed. Then a 3 stage “reefed” main parachute will open at 3,000 meters to reduce descent speed to the required level. The capsule will be recovered on the South Atlantic Ocean.