Can SpaceX’s Dragon Capsules Land on Earth Without Parachutes?

SpaceX originally proposed a daring plan to land their Dragon capsules on Earth without the use of parachutes. Instead, the capsule would rely on SuperDraco thrusters for a safer touchdown. Let’s explore the theoretical possibility and the reasons behind the shift to a four-parachute splashdown system.

Theorized Propulsive Landing with SuperDraco Thrusters

The initial plan hinged on the SuperDraco thrusters, which are normally used for abort scenarios. These thrusters would bring the capsule to a hover, allowing the landing legs to deploy from the bottom of the craft. Following that, the heat shield would ensure a soft touchdown. This innovative solution seemed promising, especially given the capsule's need for precision and safety.

SpaceX even tested this concept as early as November 24, 2015, showcasing their commitment to this technology. However, external factors such as congressional underfunding and technical challenges delayed the development of the 'Crew Dragon' spacecraft. NASA, SpaceX's customer for the Crew Dragon, showed great caution, preferring to avoid adding complexity and potential risks. As a result, the original plan was discarded.

The Four-Parachute Ocean Splashdown Solution

Instead of relying on thrusters for landing, NASA and SpaceX opted for a more conventional approach. The Crew Dragon capsule would now use four parachutes for a splashdown in the ocean. This method was chosen due to the capsule's expected weight and the fact that SuperDracos would be needed for the abort system.

The switch to a splashdown approach marked a significant shift in the mission's safety strategy. NASA deemed the use of parachutes as a safer and more reliable alternative to propulsive landing, ensuring a softer and more controlled descent into the ocean.

Design Changes and Safety Measures

The SuperDraco thrusters were designed to work perfectly, but a rare incident during a test firing on April 20, 2019, highlighted the potential risks. A nitrogen tetroxide (NTO) leak into a helium line caused a chain reaction leading to an explosion. The resulting investigation revealed that the check valve was responsible, and as a preventive measure, NASA replaced it with burst discs, which are single-use safety components.

This change meant that the SuperDraco thrusters could no longer be used for hover landings. They now fire once and are inactive, impacting the overall concept and functionality of the original landing plan.

The Future of Dragon Capsule Landings

While the SuperDraco thrusters are still used for the emergency escape system, the primary focus shifted back to parachute-assisted splashdowns. The legs designed for propulsive landings remain part of the capsule but are not used in the current operational scenario.

Despite the modifications, SpaceX continues to push the boundaries of space technology, aiming to enhance safety and reliability in future missions. The shift to a splashdown approach demonstrates how careful engineering and risk management play crucial roles in space exploration.