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, which uses hypergolic fuel to trim orbits, and the majority of payloads do use it. The purpose of the Epsilon 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 changed since then, and the umber of customers with small satellites to launch boomed. For a while there was an unmet demand for small launch services, but now so many companies have entered the market that the deficit may be turning into a glut, especially in China. We have already seen a shakeout of minor launch companies in the USA, and there could be more to come as 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.) Of course, the Epsilon is more about national autonomy than about market competition, but even for that, once some private venture in Japan manages to be more or less competitive with Chinese small launchers, the Epsilon may well be obsoleted.

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 2025.