EPSILON (イプシロンロケット) — Japan, 2013 This is another of the small solid-fuel type which has been catching on lately. It has three stages, and no interesting features. A fourth stage option is available, using hypergolic fuel. Its purpose is to cut costs, that’s all. The first stage is based on the side boosters of the H-IIA. It doesn’t get much use, flying only about once a year. In 2022, the sixth launch failed, after the first five had all been good. As the H3 comes into service, they’ll be replacing the booster with a new one, and also updating the third stage. This new version will be called Epsilon S. Its performance is about the same as the original. I was doubtful that these baby launchers were a good market strategy. Elon Musk apparently agreed with me: SpaceX’s first rocket to launch a satellite was the Falcon 1, which was about this size, and as soon as they got it working he didn’t bother making any more, despite having some waiting customers at the time. But conditions have changed since then, and the number of customers with small satellites to launch has boomed. Currently there is an unmet demand for small launch services, but now so many companies are entering the market that within a couple of years, the deficit could turn into a glut. Some in the industry are now expecting a shakeout, where the less competitive small launch ventures fail to find customers. Solid rockets in particular may be vulnerable, as there may be hard limits on how low they can cut prices. (At the same time, SpaceX’s low prices may also be shaking out some large launchers, though there’s a lot more inertia in that market, particularly since so many of the customers are governments.) SS-520 Speaking of smallness, I should mention the SS-520, a little suborbital sounding rocket with two solid-fuel stages. The Japanese stuck a third stage onto one and orbited a single cubesat with it in 2018, setting a record for the smallest vehicle to ever lift anything to orbit. This was a one-time stunt; they are not going to offer launch services on it. For the record, the rocket had a mass of 2.6 metric tons and a diameter of 0.52 meters (20.4 inches). The payload weighed four kilograms. Epsilon: mass 91 t, diam 2.5 m, thrust 2.3N, imp 2.8 km/s, solid fuel, payload 1.2 t (1.3%), cost $32M/t, record 5/0/1 through July 2023.