There are many ways that spacecraft have been reused in the past, present, and near future. Some of these methods include landing like a plane (the Space Shuttle), landing the booster on a boat (Falcon 9, Falcon Heavy, and New Glenn), catching the booster with a helicopter (Electron), or retrieving parts that parachute into the water (also Space Shuttle).
The Space Shuttle (officially known as the Space Transportation System) was an airplane-like spacecraft that was attached to the side of a large fuel tank with solid rocket boosters (SRBs) strapped to the side. The orbiter, or plane-like section, would be lifted into orbit by the powerful SRBs, which would then parachute into the Atlantic Ocean where they could be picked up by a boat. The orbiter would stay in orbit long enough to complete its mission, then re-enter the atmosphere. After the plasma layer created by re-entry disappeared, the shuttle could be piloted like an airplane back to a runway where it would land, using parachutes to slow down before the runway ended.
The goal with a Falcon 9 style recovery is to avoid all contact with seawater so refurbishment before the booster can be reflown is minimal. It is much easier to refurbish a craft that does not have corrosion as a result of seawater than one that does. A Falcon 9 was the first spacecraft to use this method on an orbital flight. The rocket launches as any other rocket would but instead of running the first stage until it runs out of fuel, the Falcon 9 shuts down its engines early. This allows the booster to do a suicide burn or hover slam maneuver. As the booster is falling back towards the ocean (Atlantic or Pacific) it can use special grids attached to its sides to steer towards an unmanned boat with a large landing platform. As the booster gets very close to the boat it fires up its engines just early enough to slow the booster so it does not hit the deck faster than a bullet. The Falcon 9, unlike a New Shepard, does not have enough throttle control to hover so this burn must be executed perfectly. After several failed attempts, SpaceX has been able to recover all but two of its boosters, totaling 66 landings of Falcon 9 boosters and seven Falcon Heavy booster landings. Blue Origin’s upcoming New Glenn rocket will land in this same way while their current sub-orbital tourist spacecraft, New Shepard, uses a similar style but it has the ability to hover and land in the desert close to the launch pad instead of at sea.
Both SpaceX and Rocket Lab are planning on catching first stage boosters. SpaceX has not released much information about how they plan to catch a rocket on the launchpad. This plan only became public knowledge when Elon Musk, the founder of SpaceX, tweeted “We’re going to try to catch the Super Heavy Booster with the launch tower arm, using the grid fins to take the load.” Super Heavy is the lower stage of SpaceX’s Starship rocket. The grid fins are waffle patterned pieces of forged steel that control the ship during its descent. The joints that the grid fins are held on with are designed to withstand very large and sudden stresses and could be upgraded to be even stronger. As a result of this information and no news from SpaceX or Elon Musk about how the catching mechanism will work, the space community has started coming up with their own ideas. Some of these designs are created as jokes. One design concept by Julius Bruton is an excellent example of one of these. This video rendering of the design shows two robotic arms mounted to a tower grabbing onto the rocket and slowly lowering it to the ground before giving it a pat on the ‘head’. The design that seems to be favored by many is a claw on the launch tower that can spin around the tower. This claw also has a mechanism to absorb some of the impact from the grid fin mounts. The ability to spin allows the claw to account for imprecise landings. The benefits of catching the rocket instead of propulsively landing (firing a few engines at a low throttle level to slow down the rocket for landing) in the launch clamps is that the forces exerted by the engines are reflected off of the launch pad and can damage the engines. If the distance between the engines and the ground is larger then there is a much lower risk of damage to the engines which in turn allows for faster turnaround times and lower costs. Rocket Lab currently does not have the capability to recover the first stage boosters of its Electron rocket. Their plan for recovering boosters is to deploy a rectangular parachute that will allow them to control the path that the rocket falls in. To catch the booster a helicopter will fly over the falling rocket with a hook dangling below it. The hook will snag the parachute, allowing the helicopter to fly back to a large boat nearby to lower the rocket onto the deck then land on a helipad. The reason Rocket Lab is pursuing this idea is to lower the cost of their rockets. When a booster can be used multiple times, the manufacturing cost can be divided among multiple launches, lowering the price. When SpaceX began to reliably land their Falcon 9 rocket the price dropped by $52.7 million. Rocket Lab has full carbon composite small satellite launch vehicles, which are much smaller and cheaper to manufacture than Falcon 9s so their price will be very low for each launch once they can be reliably caught for reuse.
SpaceX’s Starship will be the first orbital-class rocket ever to be fully reusable. This means that the upper stage of the rocket will also have to re-enter the atmosphere and be recovered. Starship will use the atmosphere to bleed off speed similar to a skydiver. Once near the landing pad, it will land by doing a “flip maneuver.” The rocket does not flip end-over-end but the rocket, which re-enters at an angle, overcorrects for its angle and then pivots back to an upright position as it touches down. This motion can be seen during the Starship SN8 test flight.
In the future, there may be more methods but for now, it looks like most companies are following SpaceX’s lead because they have been incredibly successful in reusing their Falcon 9 boosters. Only time will tell how diverse the reusable rockets may become in the future.
Freshmen Sean Harren is a staff writer for the 2020-2021 Colonel. He plays soccer and lacrosse. In his free time, he enjoys sailing and CAD modeling/3D printing.