Following Saturday’s auspicious launch and and first stage recovery, SpaceX’s Dragon spacecraft has successfully rendezvoused and docked with the International Space Station. Bringing with it more than 5,000 pounds of food, water, scientific experiments, and technology demonstrations, the company’s eleventh mission under their first Commercial Resupply Services contract is exceptional for a very unique and specific reason: the vehicle has flown before, bringing cargo to the ISS on SpaceX’s fourth CRS mission to the ISS. This accomplishment makes the Dragon currently docked at the ISS the only commercial spacecraft in human history to be launched into orbit more than once, continuing a tradition of auspicious firsts.
Slightly more than two months after the first ever successful reuse of an orbital-class rocket, SpaceX now has two extraordinary demonstrations of success in favor of the company’s pursuit of democratizing affordable access to space. Reusability is and has been SpaceX’s method of pursuing that goal for at least a decade, with Musk publicly exhorting the potential benefits of rapid and complete reusability as early as 2007. It is almost a running joke within the community of aerospace and SpaceX fans that Musk will compare commercial airlines to orbital launch services at least once every time he is interviewed, but his point is and has long been clear. If all one has to do to run a transportation service is refuel after every trip, the price of a ticket or cargo transport drastically decreases. While many have slyly laughed or dismissed this goal in the past, often using the Space Shuttle as an example of the futility of reusability as a tool for cost reduction, it is quite hard to deny what SpaceX has accomplished so far.
The reuse of a Cargo Dragon is also arguably far more significant than it may initially appear. SpaceX has not provided any concrete information on the process of refurbishing the capsule, and it is entirely unclear if the “reuse” entailed much more than furnishing the CRS-4 pressure vessel and Draco thrusters with a new trunk, solar array, external shell. It is possible that, just like SES-10, the process of refurbishing a spacecraft for the first time resulted in little to no cost savings, and that this refurbishment took anywhere from several months to more than a year, with the CRS-4 capsule returning from orbit in late 2014. However, given the absolute rarity of reused capsule-type spacecraft, the data that engineers likely gathered throughout the process of refurbishing the Dragon would arguably make the whole process worthwhile even in the worst case scenarios described above. Hans Koenigsmann, Vice President of Mission Assurance at SpaceX, also noted in a press conference following CRS-11’s launch that the refurbishment of the capsule was somewhat uneventful, stating that the CRS-4 capsule had no unanticipated damage from the rigors of reentry and ocean landing and that SpaceX was already ready to consider using the capsule a third time. It’s likely that SpaceX will begin to rely more heavily on Cargo Dragon reuse as they refocus a majority of their manufacturing efforts on Dragon 2.
SpaceX and Musk’s (in)famous ultimate ambitions are to make humanity a multiplanterary species, partly as a way to combat the extinction risks that an asteroid or comet strike pose, and partly because it is simply a staggering challenge that has the potential to make many humans “excited to wake up in the morning”. In order to make this happen, Musk saw that access to orbit was far too expensive for a colony on another planet to ever be sustainable, and that resuability was the only immediately obvious and accessible method through which the price to orbit could be decreased by several magnitudes. SpaceX is now almost routinely recovering Falcon 9 first stages when the mass of the payload allows it, and with a fifth and final version or “Block” of the vehicle optimized for rapid reuse set to debut later this year, Musk and others at the company have begun ruminating once more about the possibility of recovering and reusing the second stage of the Falcon 9. Benchmarked somewhere around 30% of the price of the vehicle, routine loss of the second stage effectively prevents the price of the Falcon 9 from dropping much below $20-30 million US dollars. While a nearly 50% or greater reduction in price would be an exceptional accomplishment, it is still far from from the multiple orders of magnitude reduction Musk hoped for when he set out to develop reusable rocketry.
This is where the reuse of Dragon pops its head up. With second stage recovery now being considered theoretically and Dragon 2 (Crew Dragon) preparing to begin regular launches in either Q4 2017 or Q1 2018, SpaceX has a good deal of experience to gain from learning how to safely and rapidly recover and reuse vehicles reentering the atmosphere at orbital velocity. Compared to recovering the first stage, this is another endeavor entirely. The fastest speed at which a recoverable first stage can ever realistically reenter the atmosphere is currently capped at around 5200 mph (2300 m/s), and is usually much closer to 3000 mph. An orbital capsule like Dragon, however, enters the atmosphere from Low Earth Orbit (LEO) at around five times that speed, typically close to 16,000 mph. In the context of recovering the second stage of Falcon 9, one must consider that most of SpaceX’s commercial manifest is made up of geostationary satellites, which require more energy to reach a higher orbit, and consequently would require the second stage to survive even higher reentry velocities in order to be recovered.
Returning from Mars, as SpaceX’s Interplanetary Transport System would have to, results in even higher reentry velocities of at least 25,000 mph for a reasonably quick journey. This is the most important detail in explaining the true value of simply reusing a Dragon capsule as SpaceX has just now done. By taking its first steps towards routinely reusing truly orbital spacecraft, SpaceX is advancing their knowledge reusability in practice and consequently taking concrete steps to prepare themselves for the difficult challenges that lie ahead in their pursuance of enabling sustainable colonization of Mars. Dragon 2 (Crew Dragon) promises to eventually rid the refurbishment process of the many headaches that salt water intrusion undoubtedly creates by returning via supersonic retropropulsion to a landing pad, much like Core 35 did this past Saturday.
Looking slightly further into the future, SpaceX has already announced plans to launch two unnamed private customers in a Dragon 2 on what would likely be a circumlunar free return trajectory, or around the Moon and back. The reentry velocity would be very similar to the velocity required to return to Earth from Mars, and certainly much faster than any reentry from geostationary orbits of Earth. If SpaceX manages to successfully and reliably recover and reuse orbital vehicles reentering at such high velocities, then the company will have made extraordinarily promising progress towards achieving their central goal of drastically lowering cost to orbit and thus enabling humanity to gain footholds on other planets.
So, take this Dragon reuse as you will. It may well be a major step along the way to colonizing Mars, or it may simply be an exciting practical implementation of SpaceX’s philosophy of reuse. Either way, this is a Dragon that is certainly worth celebrating.