Last changed: V0.2 - 17-04-2020

Sounding Rockets

Sounding rockets are rockets that fly into space but do not enter an orbit. They often serve as testbeds or as a cheaper alternative for orbital missions. As the experiments need to be returned to earth safely, they are often equiped with a parachute recovery system.

Developed in collaboration between mostly DLR, and Kayser-Threde GmbH (now part of OHB Systems AG), the ERS is a parachute-based payload recovery system designed to bring sounding rocket payloads safely back to Earth. It has been a key component in sounding rocket programs such as TEXUS, MASER, and MAPHEUS, ensuring the retrieval of expensive or irreplaceable scientific equipment and samples.

The ERS started development in 2006 in an effort to gain more independence from the North American market by replacing the US-made ORSA (Ogive Recovery System Assembly). At its core, the ERS is built to recover payloads weighing up to approximately 450 kilograms, housed in cylindrical bodies with diameters up to 438 mm. The system’s design follows a classic two-stage parachute approach.

The second stage consists of a cross-type canopy parachute with a nominal reference area of 147 m², reefed to 8% for 10 seconds. This canopy ensures highly stable final descent conditions, minimizing payload oscillations and reducing landing damage. During nominal missions, deployment occurs at approximately 50 m/s by severing the drogue harness with a pyrotechnic guillotine cutter mounted at the center rear of the parachute container. The released drogue extracts the main parachute via an extraction line. Once fully deployed, the main parachute reduces the landing velocity to below 8 m/s, with opening loads remaining under 2.5 g.

The system is housed within a forward-section ogive — the nose cone of the rocket — which is designed with a fineness ratio of around 3:1. The tip of this ogive is jettisoned once the rocket reaches exo-atmospheric conditions after apogee. This separation clears the way for safe deployment of the drogue parachute during descent, preventing interference from the outer shell and ensuring reliable parachute inflation.

Activation of the ERS is controlled by a combination of electronic and environmental triggers. A barometric switch typically initiates the recovery sequence once the payload descends to an altitude of around 4.6 kilometers. Pyrotechnic devices — powered by independent batteries and backed up with redundant systems — then deploy the drogue parachute. Once the payload is sufficiently stabilized and slowed, the main parachute is deployed to further reduce the descent rate.

One of the system's key strengths is its adaptability. Many of MORABA’s missions are launched from the Esrange Space Center in northern Sweden, where payloads often land in remote wilderness or, in some cases, in open water. The ERS is equipped to handle both scenarios. For sea landings, a specially designed flotation system is integrated into the parachute structure. This system inflates passively using ram air pressure during descent and is robust enough to keep the payload buoyant even if the outer shell is compromised. It features dual chambers for redundancy and is equipped with sealed valves to prevent water ingress after splashdown.

Locating the payload after landing is another challenge that the ERS addresses. The recovery unit includes various tracking aids, such as VHF radio beacons, strobe lights, and — increasingly — GPS and Iridium-based satellite communication systems. These tools significantly reduce the time needed to locate and retrieve the payload, even in difficult terrain or adverse weather conditions.

Over the years, the ERS has undergone numerous improvements. Efforts have focused on reducing packing volume, optimizing parachute materials, and improving the durability of the flotation and electronics systems. For sea recovery, prototypes have been tested in ESA’s Neutral Buoyancy Facility and other environments to validate performance under realistic conditions.

What makes the ERS particularly effective is its reliability across a wide range of mission profiles. Whether launched for atmospheric studies, materials science, or biological research, the recovery system provides a consistent, proven method for bringing critical payloads back intact. Its performance is crucial not just for mission success, but for the continuity of research programs that depend on analyzing returned samples or reusing experimental hardware.

Named in honour of the driver from the British car show Top Gear [123] is/was an attempt by Armadillo aerospace to create a reusable launcher using parachutes. The first STIG-A launched in 2011 and was the first of three flights for this model. The launcher has a single LOX/Ethanol stage for sub-orbital flight with a target altitude of about 100km.

For the recovery of the launcher, uses a two-stage system and recovers the entire rocket. It deploys a ballute drogue parachute attached to both the nosecone and the propellant tank with the engine at apogee. This performs the initial deceleration from entry into the atmosphere as a ballute is deployed usually before entry. The tank and engine are detached from the ballute, and a parafoil is deployed following the ballute phase. This safely lands the engine and tank. The nosecone stays attached to the ballute and decelerates because of the loss of the engine and tank to a safe landing speed [120,122].

The STIG-A performed three flights, of which at least one seems successful, and the other two are unknown [115,117]. After this, the performance of the launcher was increased, which led to STIG-B. Again three flights were performed. However, all flights at least failed the recovery part of the flight due to failed deployments. After the last STIG-B launch, Armadillo was bought by EXOS Aerospace which continued with the STIG-B design and improved it into the SARGE launcher[6]. Four flights were performed with the SARGE launcher. All flights again had issues. However, this time the failures occurred during the powered phase of the flights. Often, during the initial seconds of the flight, the tank was successfully recovered at least once [119].

The Miura 1 rocket aims to fly end of 2020 and can bring 100 kg payloads to 150 km. The rocket is equipped with a parachute system for full rocket recovery. According to a paper presented at EUCASS2019, the drogue parachute opens at 5 km, and the main parachute opens at 3 km. The rocket performs what is described as a "passive aerobrake descent", it is unclear what is meant by this. The parachutes onboard Miura 1 are a 3m Conical Ringslot drogue and a 15.4m Hybrid Slotted Pyloconical main parachute. The main parachute is reefed to 10% upon opening. Several drop tests have been performed in the US. As the sounding rocket is meant to be fully reused, the drogue parachute is equipped with a kill line. This line contracts the drogue parachute killing the drag it generates. 

In October 2023 PLD Space launched Miura 1 on a first mission. The apogee of the flight was lower than expected, according to statements this was due to range constrictions. After the flight, the rocket landed safely, but was not found after flight.