Challenges of Reusable Spacecraft

Introduction

For a long time, the main method for outer space exploration was done by sending payloads containing machines and organisms into atmospheric orbit. However, the high cost of sending rockets to space has long been an underlying issue within this field, significantly limiting the amount of exploration and research that can be conducted. Therefore, recently, scientists have begun diving into the concept of RLVs (Reusable Launch Vehicles). That is, rockets that can both launch themselves into orbit and return back to Earth, landing back onto a landing pad without sustaining significant damage or losing pieces. There are many challenges to implementing these procedures, however, due to its engineering challenges as well as the increased costs, and unforeseen risks.

Technical Challenges/Engineering Barriers

Engineers must overcome many significant hurdles in order to integrate reusable rockets into aerospace. Eric Brown from the MIT Industrial Liaison Program wrote on MIT News on Zack Cordero, an MIT professor whose research is dedicated to learning more about reusable rocketry, and rockets that want to return back to Earth with minimal damage “must integrate components and design elements that allow the vehicles to automatically maneuver for a soft landing. They also require greater thermal protection to withstand extreme aerothermal heating during reentry.” Cordero himself noted that “propulsion devices need to be designed differently for reusable rockets,” explaining how “with reusable liquid propellant rocket engines, you must ensure safe operation over multiple flight cycles and ease off on performance to reduce stress” (Brown). Thus, not only do RLVs require more intricate and complicated design elements compared to previous rockets, they also must have greater thermal protection as well as propulsion devices that can be reused. 

Cordero doesn’t shy away from sharing the problems that he is currently facing: he reports a “wide spectrum of failure behaviors,” from cracking thrust chambers to extended wear on turbopumps, chambers, and nozzles to oxygen compatibility and metal fires, the number of difficulties he faces is nigh infinite. Cordero even goes as to say “new heavy lift launch vehicles will continue to fail unless there are fundamental advances in materials technology,” (Brown) suggesting that, unless there are stronger and lighter materials that can be manufactured for these rockets, further advancement into this field is relatively futile, adding yet another seemingly-insurmountable obstacle to the engineers’ paths. 

Economic Difficulties

In implementing RLVs, there are high costs associated with many of the materials that are needed to construct these massive aeronautic ships, even more so if they are expected to safely return back onto our world with only chip damage. While these high costs may seem like an initial high price to pay, scientists and researchers actually suggest that they will actually pay off several times over in the long run. The U.S. government itself has spent a large sum of money on this. “The U.S. Air Force (USAF) spent approximately $115 million on studies for RLVs between 1992 and 1997. During this period, NASA‘s investment in RLVs was more than $ 1 billion” (Ward). This wad of cash pooled by the U.S. government could have been supplied to other organizations or projects that may have had more success in improving society or breakthroughs in sciences compared to RLVs. After this, however, the U.S. continued to fund much more research on RLVs in hopes of creating the first truly useful RLV in projects such as the Delta Clipper Experimental (DC-X), NASA X-33  and X-34, and the USAF Space Maneuver Vehicle (SMV).

Even so, the money has not entirely gone to waste. Space Content Developer and Vice-President of ESROMAGICA Shreya Mane writes on RLVs “significantly lowering the cost per launch and enabling a more sustainable and frequent launch schedule.” Not having to rebuild a rocket for every mission, Mane finds, also “reduces waste and conserves resources, as fewer materials are needed to build new rockets for each mission” (Mane). The use of to-be-implemented reusable spacecraft will enable much more ambitious projects and support growing demand for space exploration. Currently, rockets cost upwards of tens of millions of dollars. For example, “NASA’s Space Launch System (SLS) is estimated to cost over $2 billion per launch” (NSTXL)  states the National Security Technology Accelerator (NSTXL), but using an RLV rather than a traditional rocket makes launches “up to 65% cheaper.” In addition to using less resources than traditional rockets, RLVs also “use less fuel than expendable rockets” making them comparatively even better for the environment. Using RLVs, space exploration can be more time and cost-efficient than ever before, shining a light on a possible pathway for aerospace.

Safety and Risk

As previously mentioned, however, there are also many safety issues within the industry revolving around explosions and fires that may harm both man and machine alike. Cordreo’s issues with turbo pumps are especially intriguing. He asserts that, in a turbopump, there could be “a blisk failure” or “a rub between the rotor and casing.” He also identifies that the different RLV engines are “vulnerable to particle impact ignition” all of which “lead to a metal fire and a catastrophic, single-point failure mode that results in the vehicle exploding” (Brown). This easily-exploitable vulnerability within the rocket is a serious issue within the development of RLVs. Another possibility for error that could lead to irreversible damage is oxidizer compatibility with full-flow staged combustion (Raptor) and oxygen-rich staged combustion (BE-4) engines. Cordero notes the presence of “high-temperature, high-pressure oxygen gas” within the rocket, “which can drive metal fires and rapid energetic failure modes” (Brown). 

Moreover, the unbelievably high temperatures within a rocket before takeoff “generates incredible stresses that cause conventional coatings to pop off,” adding yet another risk to these rockets that must be reduced if not resolved entirely. A staff reporter from BroadcastPro has concluded that, while there may be many risks and dangers revolving reusable rockets, researchers are tackling this problem head-on. With Cordero working on ignition-resistant materials, oxygen-rich turbopumps, and more, the reporter predicted that his research will dive into “the reliability problem, focusing on extending the lifespan of reusable rockets, while simultaneously reducing the risk of catastrophic failure” (BroadcastPro). Therefore, even with all the dangers hanging near, it is probable that we will soon see more and more RLVs in the news and perhaps even in our daily lives.

Conclusion and Outlook

Currently, the most successful RLV project has been the Falcon 9 by SpaceX. It is the world’s first orbital-class RLV, successfully taking people and payloads into space. It has “achieved multiple successful landings and relaunches,” according to NSTXL, and “Falcon 9 booster can be reused over 10 times, with minimal maintenance between flights,” (NSTXL) demonstrating the incredible progress that, even with all the challenges that the field has faced, has been achieved in recent decades. Its success has been followed by Blue Origin’s New Shepard and companies like Rocket Lab’s Electron Rocket, lighting the spark for a transformative revolution in aerospace, marking the start of a new era in space exploration.

Works Cited

BroadcastPro. "Space on a shoestring." BroadcastPro, 17 Sept. 2024, www.broadcastprome.com/news/satellite/space-on-a-shoestring/. Accessed 21 Dec. 2024.

Brown, Eric. "Boosting rocket reliability at the material level." Massachusetts Institute of Technology, MIT News, 28 Nov. 2023, news.mit.edu/2023/boosting-rocket-reliability-material-level-1128. Accessed 21 Dec. 2024.

Global Aerospace. "Global Aerospace Offers Valuable Insights on the Revolution of Reusable Rockets and Their Impact on the Space Industry." GlobalNewswire, Global Aerospace, 23 Nov. 2024, www.globenewswire.com/news-release/2024/11/24/2986297/0/en/Global-Aerospace-Offers-Valuable-Insights-on-the-Revolution-of-Reusable-Rockets-and-Their-Impact-on-the-Space-Industry.html. Accessed 21 Dec. 2024.

Mane, Shreya. Overview on Reusable Space Launch System. Aug. 2024. ResearchGate, www.researchgate.net/publication/383181934_Overview_on_Reusable_Space_Launch_System. Accessed 21 Dec. 2024.

National Security Technology Accelerator. "Reducing the Cost of Space Travel with Reusable Launch Vehicles." Reducing the Cost of Space Travel with Reusable Launch Vehicles, National Security Technology Accelerator, 12 Feb. 2024, nstxl.org/reducing-the-cost-of-space-travel-with-reusable-launch-vehicles/. Accessed 21 Dec. 2024.

Ward, John E., Jr. Reusable Launch Vehicles and Space Operations. Montgomery, Alabama, Air University, May 2000, www.airuniversity.af.edu/Portals/10/CSAT/documents/OP/csat12.pdf. Accessed 21 Dec. 2024. The Occasional Papers 12.