Challenges of Ablatively Cooled Hybrid Rockets for Satellites or Upper Stages

Abstract

Ablative-cooled hybrid rockets could potentially combine a similar versatility of a liquid propulsion system with a much simplified architecture. These characteristics make this kind of propulsion attractive, among others, for applications such as satellites and upper stages. In this paper, the use of hybrid rockets for those situations is reviewed. It is shown that, for a competitive implementation, several challenges need to be addressed, which are not the general ones often discussed in the hybrid literature. In particular, the optimal thrust to burning time ratio, which is often relatively low in liquid engines, has a deep impact on the grain geometry, that, in turn, must comply some constrains. The regression rate sometime needs to be tailored in order to avoid unreasonable grain shapes, with the consequence that the dimensional trends start to follow some sort of counter-intuitive behavior. The length to diameter ratio of the hybrid combustion chamber imposes some packaging issues in order to compact the whole propulsion system. Finally, the heat soak-back during long off phases between multiple burns could compromise the integrity of the case and of the solid fuel. Therefore, if the advantages of hybrid propulsion are to be exploited, the aspects mentioned in this paper shall be carefully considered and properly faced.

Modeling and CFD Simulation of Regression Rate in Hybrid Rocket Motors

“…Several aspects of hybrid rockets make them an attractive technology for next-gen propulsion, such as simplicity, low cost, safety, reliability, environmental friendliness, thrust modulation and the ability to be restarted [1][2][3][4][5][6]. Nevertheless, sufficient maturity has not yet been attained and nowadays, no system has reached full operational status, even if this could happen in the near future [7][8][9][10][11][12][13]. In this frame, Computational Fluid Dynamics (CFD) is a powerful tool that can help develop a high-performance solution and increase the TRL of hybrid rocket motors in a cost-effective way [14].…”

Review of Alternative Sustainable Fuels for Hybrid Rocket Propulsion

“…Several issues have always hindered hybrid rockets from reaching operational status, but this topic is out of the scope of this paper, and an extensive literature is already available e.g., [24][25][26][27][45][46][47][48][49]. At the moment, a few companies have serious plans to develop hybrid launch vehicles, such as HyImpulse (Neuenstadt am Kocher, Germany) [50], Gilmour Space Technologies (Helensvale, Australia) [51], INNOSPACE (Sejong-si, Republic of Korea) [52], TiSPACE (Taiwan) [53], DeltaV (Turkey) [54][55][56], and NAMMO (Raufoss, Norway) [57], while many others have similar ambitions but are still behind in large scale development (Equatorial Space Systems [58], Vaya Space [59], Hybrid Propulsion for Space [60] .…”

Special Issue “Hybrid Rocket (Volume II)”

“…Furthermore, by designing the thrust profile appropriately, the acceleration environment of the payload can be made milder, which is also desirable for practical use as an upper stage engine. In this special issue, Barato [6] has reviewed the challenges in the design of hybrid rockets for upper stage engines from a new perspective in terms of ablative cooling, packaging, and fuel regression rate; Kamps et al [7] have studied the suitability of various oxidizers for hybrid rockets when the on-board envelope is limited to one cubic meter and showed that both hydrogen peroxide at 85% and nitorus oxide are superior to LOX.…”