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GRAIL Report Summary

Project ID: 638719
Funded under: H2020-EU.


Reporting period: 2015-02-01 to 2016-01-31

Summary of the context and overall objectives of the project

Solid rocket motors are today the most cost effective, competitive and reliable propulsion technology for space launch systems. State of the art solid rocket propellants are based on the oxidizer ammonium perchlorate, AP, and aluminium powder, embedded in a polymer binder matrix. AP has been used since the 1950s and is in many ways an excellent oxidizer. However, AP has a negative impact on the environment and on personal health due to ozone depletion, thyroid gland interference and acid rain formation.
Sustainable Development has become a top priority on the European and international agendas. With ever increasing environmental concerns, industries in Europe need to adapt to more restrictive environmental legislation in order to stay competitive and to enhance social acceptance. The space industry is in this case no exception which is reflected by ESA´s Clean Space Initiative and ESA´s Green Propulsion Harmonisation Process.
The influence of AP on the environment and on personal health is debated by the solid rocket motor industry, which in general considers no imminent reason to replace AP. One reason for this might be that currently there is no viable alternative.

The ambitious goal of this proposal is thus to develop a green alternative to AP.

The objective of the GRAIL project is to determine if it is feasible to replace AP by using a mixture of the new high energy density oxidizer ammonium dinitramide, ADN, and the low cost oxidizer ammonium nitrate, AN.
This will be done by developing a solid propellant based on ADN/AN, aluminium powder and a polymer binder. To obtain high performance high energy fuels such as aluminium hydride and nano aluminium will also be used.
The high energy density green solid propellant developed will be compared with state of the art solid propellants with respect to:

• Safety
• Performance
• Cost

to determine if replacing AP with ADN/AN is a feasible option. The results will serve as important input for decision makers when considering development of future European launch systems.
Successful development of a high energy green propellant will lead to a breakthrough in solid rocket propulsion technology with respect to performance, competitiveness and environmental impact.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the first project period the work has mainly focused on development, processing, production and characterization of the chemicals needed for the propellant development. This include improving the methods to produce ADN particles with suitable morphology, production of phase stabilized AN, and characterization of the oxidizer particles produced. The high energy density fuels to be used have been characterized and binder materials have been developed. Encouraging results from the system analysis performed show that the suggested green solid propellant has the potential to exceed the performance of current AP based propellants.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Since the selection of AP as the solid oxidizer of choice in the 1950s, the main development of solid propellants has focused on new polymers. Since the 1970s, when the polymer HTPB was introduced, the development has been incremental. Introduction of an alternative to AP will lead to a ground-breaking development step. Apart from being more environmental friendly, ADN/AN has the potential to increase the performance beyond that of current AP based propellants.

Helth issues related to AP is in the US adressed by the Environmental Protection Agency, EPA, and in Europe by the European Food Safety Authority, EFSA. Currently, EPA is developing a proposed national primary drinking water regulation for perchlorate, and the European Commission has confirmed that EFSA will be requested to assess the need to establish an Acute Reference Dose for perchlorates. In view of a possible Union legislation following the EFSA opinion, all EU Member States are currently requested to monitor the presence of perchlorate in food. How these regulations will influence the space propulsion industry is not clear. However, the regulations will not improve the public acceptance of using perchlorates.

ESA, with its Clean Space Initiative, has increased its attention to the environmental impact of space activities, including its own operations as well as operations performed by European industry in the frame of ESA programs. This is also reflected by ESA´s Sustainable Development report (SP-1319, January 2011) where it is stated that “As a public international organisation, ESA needs to show determined commitment vis-à-vis the environment, both in its internal functioning and also in its core business activities”. In line with this, a feasible green solid propellant alternative might in the future influence ESA’s acceptance of using AP.

The global ozone loss caused by rocket emissions is dominated by solid rocket motor emissions due to the use of perchlorate. However, currently the contribution to ozone layer depletion is insignificant compared to the depletion caused by other ozone depletion substances (ODSs). As the space industry grows and other ODSs fade from the stratosphere, ozone depletion from rockets could become significant. This raises the possibility of regulation of space launch systems in the name of ozone protection. Such regulations would be devastating to the space industry and for global economic growth in general. To prevent such a regulation to be put into force, the space propulsion industry can be proactive by developing green solid propellants.

With ever increasing environmental concerns and expected more restrictive environmental legislation, it is questionable if AP will be an option for the future. By being proactive, the European solid propulsion community can prepare and develop alternatives. This will foster the industry and the European capability of accessing space. If it is found that ADN/AN is not a possible alternative, this will also be a very important message to ESA, National Space Agencies and to the industry. The results will thus in any case serve as important input for decision makers when considering development of future European launch systems.

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