Launching and retrieving spacecraft from low-Earth orbit or beyond is a remarkably capital-intensive, technologically challenging, and hazardous venture. Only four entities have successfully performed both portions of the task – the United States, the Soviet Union, the People’s Republic of China, and SpaceX.
SpaceX (Space Exploration Technologies Corp.) needs little introduction as the company has entered popular culture since its founding in 2002. As any Elon Musk enterprise, its mission can be boiled down to “changing the course of human history”. So far, the American company has been remarkably successful in leading the newly fledged commercial spaceflight sector as well as providing access to space for the United States following the retirement of the Space Shuttle.
After securing NASA’s Commercial Orbital Transportation Services (COTS) contract, SpaceX developed its Falcon 9 launch vehicle, which through incremental improvement has become the cheapest and most cost-efficient medium-lift rocket in existence. This is in part due to the company’s proprietary Merlin engine, which provides an unprecedented thrust-to-weight ratio. The Falcon 9’s most recent iteration, v1.1, attempted what many had envisioned but could not implement due to inordinate engineering challenges – a fully and rapidly reusable first stage.
The first stage is the portion of the vehicle that stores the vast majority of the fuel needed to overcome Earth’s gravity and deliver the second stage to the edge of space. The Falcon 9’s first stage never reaches orbital velocity and can thus be engineered to slow down following separation via reverse burning three of its nine Merlin engines, fall back to Earth on a controlled trajectory, and land propulsively in the precise spot it launched from with the aid of landing legs. This is the basic design SpaceX is striving to perfect and implement. As intricate and daunting as the task seems, coordinating a series of burns and guiding the vehicle back to the launch pad is hardly the difficult part. The primary issue lies in weight management. In order to execute these maneuvers, the first stage needs to be equipped with additional hardware and fuel, the weight of which roughly equal the weight of a payload. Thus, the herculean challenge lies in making the landing system, as well as the rest of the rocket, light and efficient enough to still leave a good percentage of total weight for a decent-sized payload.
Implementing reusability of the second stage is more difficult as that stage carries the payload to orbit or beyond, and would require extra fuel in addition to a thermal protection system (heat shield), retro rockets, and landing gear to reenter Earth’s atmosphere and return to the launch pad. SpaceX plans to implement first stage reusability in the near-term with full reusability following some years after.
Falcon 9 v1.1’s maiden flight in October, 2013 served as the first commercial launch demonstration of SpaceX’s development of this capability. The initial retro burn worked as planned and the first stage safely reentered – an enormous step in the right direction.
A second test was performed during the CRS-3 cargo resupply mission to the ISS in April, 2014. The first stage’s retro burn was followed by a stable controlled descent, deployment of landing legs, and soft propulsive landing over the Atlantic Ocean. The test was a tremendous success and marked yet another first for the industry. A third test is expected within months.
Additionally, SpaceX has been touting its vertical takeoff vertical landing (VTVL) test vehicles, used to simulate a first stage soft landing. Two VTVLs have been developed for this purpose – “Grasshopper”, a now retired single-engine vehicle, based on the original Falcon 9’s first stage; and “Falcon 9 Reusable” (F9R), a three-engine vehicle, based on the improved Falcon 9 v1.1’s first stage. The vehicles have performed a number of remarkable demonstrations involving takeoff, hovering at certain altitudes, lateral movement, and powering back down to the launch pad. F9R’s latest flight reached a record altitude of 1000 meters. A third vehicle is in development that will reach higher altitudes, attain reentry velocities, and come even closer to simulating a first stage landing. The tests demonstrate unprecedented guidance capabilities and have garnered a tremendous amount of interest and millions of views on SpaceX’s YouTube channel.
Why is reusability important? It has the potential to decrease the enormous cost of access to space one hundred-fold. Falcon 9 is already several times cheaper than the competition, but such savings will seem paltry if reusability is perfected. The cost of a rocket to the cost of its fuel is in excess of 99 to 1. If a $50 million rocket was not expended on reentry, but instead landed intact on the pad minutes after launch, the cost of reusing it would be minuscule compared to the cost of building and transporting a new vehicle. This is one of many reasons SpaceX is on the radar of private companies and governments that have a stake in easy and cheap access to space. Reusability has the potential to give the company an enormous advantage in the aerospace industry, and truly alter humanity’s presence in space.