The history of Japanese reusable rocket R&D came up in my interview on @tmro last weekend. It’s a subject that’s pretty unknown (even within Japan), so it might be worth a bit more of a deep dive. Still a twitter rookie, so I’ll take the thread function for a test drive! (1/14) 
@tmro In 1993, the Japanese Rocket Society started a space tourism study. The goal was to investigate a range of requirements for a commercial airline-style space transportation industry. They looked at engineering, economics, safety/regulations, operations, etc. (2/14)
@tmro The study continued for the rest of the 90’s, and resulted in the “Kankoh Maru” concept - VTVL SSTO rocket capable of ferrying 50 passengers to orbit, with a cadence of 270 flights/year. Kankoh Maru would be lifted by 12 LH2/LOx engines and tip the scales at 550 ton. (3/14)
@tmro The Kankoh Maru never materialized, but some of the people involved in the study at @ISAS_JAXA continued with technical and operational studies. Inspired by the then-recent DC-X project in the US, they created the RVT - a small VTVL rocket testbed for reusable research. (4/14)
@tmro @ISAS_JAXA The RVT (Reusable Vehicle Testing) was used to “learn the art” of reusable rockets - they focused not only on technical/engineering issues, but also operations/ground handling. From 1998 to 2009, a series of flight tests were conducted at Noshiro Testing Center in Akita. (5/14)
@tmro @ISAS_JAXA Over the course of the program, 4 prototypes were built and tested. These vehicles progressively became more advanced. RVT #1 used a bare airframe, aluminum tanks and a pressure-fed engine. RVT #4 had a full aeroshell, composite tanks and an expander-bleed cycle engine. (6/14)
@tmro @ISAS_JAXA The RVT program allowed ISAS (now part of @JAXA_en) to develop knowledge and hands-on experience in reusable rockets. Notable developments included propulsive landing aerodynamics, streamlined ground turnaround and reusable engine technology. But they weren’t done yet. (7/14)
@tmro @ISAS_JAXA @JAXA_en In the mid 2000’s, ISAS began planning a “successor” project to the RVT. A project which would combine continuing reusability R&D with a practical application: The Reusable Sounding Rocket. Eventually, the goal would be to replace JAXA’s expendable sounding rocket fleet. (8/14)
@tmro @ISAS_JAXA @JAXA_en The initial reusable sounding rocket design called for the capability to take a 100kg payload to an apogee of 100km. Capabilities such as impact-free payload retrieval and hover-at-altitude could push the envelope in terms of what could be achieved with sounding rockets. (9/14)
@tmro @ISAS_JAXA @JAXA_en The reusable sounding rocket would be powered by 4x 40kN LH2/LOx expander-bleed cycle engines. Reusability was key in this engine design: long life (100 flight cycles), maintainability, health monitoring (for safe mission aborts) and deep throttling were all factored in. (10/14)
@tmro @ISAS_JAXA @JAXA_en Another focus was aerodynamics. The reusable sounding rocket would re-enter the atmosphere in a nose-first orientation, then use control surfaces to deliberately induce aerodynamic instability, tumbling into a base-first orientation before stabilizing itself for landing. (11/14)
@tmro @ISAS_JAXA @JAXA_en Unfortunately, it seems like the reusable sounding rocket project has been put on ice for now - I don’t know why, and I think it would be unfair to speculate. The good news is that the team is still active, with a new project underway. Enter the RV-X. (12/14)
@tmro @ISAS_JAXA @JAXA_en The RV-X borrows from a lot of the reusable sounding rocket knowledge and technology, but on a smaller scale. It will use a single 40kN LH2/LOx engine, fly to an altitude of 4-5km, perform the “turnover” maneuver, and land vertically. Flight tests are scheduled for 2020! (13/14)
@tmro @ISAS_JAXA @JAXA_en Do you want to know more about Japan’s reusable rocket research, or JAXA’s activities more generally? If there’s interest, I’d like to do more here - maybe articles or interviews? Let me know what you think!
Sources:
bit.ly/32wz6UP
(14/14)
Sources:
bit.ly/32wz6UP
(14/14)
