1) Sustainability Problem: Health and Safety (Radiation)

Rocket engines powered by mainstream hydrocarbon propellants release black carbon into the stratosphere, which is the second layer of the atmosphere. Because the particles are literally black, they absorb light and warm the stratosphere. These warmer temperatures accelerate the chemical reactions that deplete ozone, which we know protects us from harmful radiation. While total black carbon emissions from global space activity are not yet at high enough levels to have a significant impact, the global launch rate is experiencing a surge and is expected to continue increasing. Without any preventative or mitigative measures, the ozone depletion and corresponding radiation from aerospace activity could cause serious adverse effects for the human population.

2) Article Titles: “The Policy and Science of Rocket Emissions” and “Will hydrogen power the future of aerospace?”; Article Websites: Aerospace.org and Wha-international.com; Article Links: https://aerospace.org/paper/policy-and-science-rocket-emissions; https://wha-international.com/will-hydrogen-power-the-future-of-aerospace/

• Hydrogen fuel is readily available and can be produced efficiently. (WHA International)
• Hydrogen fuel burns cleanly and has the potential to have a 100% clean energy cycle if it is produced using renewable energy sources. (WHA International)
• Hydrogen-based rocket fuel has no black carbon emissions and performs better as a propellant than other hydrocarbon fuels. However, it is more difficult to work with than other propellants because of its sensitivity. It is also low density, requiring a larger tank and more weight which is disadvantageous when trying to get the rocket off the ground. Finally, it requires much cooler storing temperatures. (Source: Martin Ross [my manager at The Aerospace Corporation, personal interview).

3) Organizational Stakeholders

Transitioning the aerospace industry to hydrogen fuel from hydrocarbon propellants will require research, acceptance and support, and changes in infrastructure. This means that the following stakeholders will be involved:

• Aerospace engineers to adjust the actual rocket engines to use hydrogen propellant
• Climate and atmospheric scientists to continue monitoring and researching the effects of rocket engine emissions on the stratosphere and other layers of the atmosphere not so well understood
• Communication experts to translate the science to policy makers and make them understand the urgency of the situation
• Policy makers so that policies can be implemented to make the transition
• Aviation experts that have used hydrogen fuel to make connections between airplanes and rockets and this specific use case

4) Implementation Steps

As mentioned in the stakeholder section, making this transition will require lots more research as well as communication and changes in infrastructure, not to mention significant costs. Therefore, the following steps should be implemented:

• Teams should be created to combine experts in aerospace, climate/atmosphere science, aviation, and policy. All perspectives should be accounted for and professionals from various fields should work together to implement the hydrogen technology to ensure that adverse effects in other areas are not being created.
• Before implementing changes in infrastructure to accommodate hydrogen fuels only, research should be completed on other clean fuels to determine if there are even more ideal options. While hydrogen seems like a good fuel to use, there is always a need to continue searching for even better ones.
• Financial modeling should be performed to determine how much it would cost to make the infrastructure and rocket engine modifications to accommodate hydrogen fuel.