Commercial Rockets

TAURUS / MINOTAUR — USA, 1994

The Taurus is the second commercial rocket from Orbital Sciences. This one launches from the ground, with a solid fuel booster much bigger than that of the Pegasus (though still small compared to most of its competition). The Taurus is a variation of the Minotaur series, which has various models derived from the Minuteman and Peacekeeper ICBMs. They didn’t just copy the ICBM designs — as the Russians did with START, they actually recycled old booster cores as the missiles were decommissioned by the Pentagon. There is a large supply of these now being stored in military warehouses. Unfortunately for this brilliant plan, however, Congress decided it would be anticompetitive to allow the contractor recycling these old solid rockets to be able to underprice the other launch providers, so they made a rule that these recycled boosters could only be used for governmental launches, not commercial ones. So the Minotaur series are the government’s main small launch system, replacing the long-discontinued Scout. You’d think that would be a good useful role, since they’re abundant and cheap, but it gets surprisingly little use.

There are many models in the Minotaur series. The I and II are based on old Minuteman missiles, using their first and second stages with new upper stages. The I adds an Orion 50XL and an Orion 38, both as used in the Pegasus, with the option of a liquid kick stage. It can orbit 0.58 tons. The II has a choice of third stages and no fourth stage, and is for suborbital use only. The Pentagon liked to use it as a practice target for ICBM defense techniques. The III is based on a Peacekeeper’s first three stages, which are substantially bigger than those of the Minuteman. It’s also a suborbial rocket. The Minotaur IV is where they get serious: it uses three Peacekeeper stages and an Orion 38 (plus optional kicker) to huck 1.7 tons into orbit. The V uses a heftier Star 48V fourth stage and the Orion 38 as a fifth, and can do geosynchronous transfer orbits with up to 0.56 tons of payload. These missiles have huge thrust-to-weight ratios and take off with terrific speed; I’m told they reach the speed of sound in about fifteen seconds. You can see why that would be desirable in an ICBM; for other payloads, you’d sure better be ready for some G forces.

The Taurus is the commercialized version of this kind of launcher. It replaces the Peacekeeper booster stage with a civilian equivalent which can legally be used for private sector customers. This stage is known as the Castor 120 — Castor (like Star) being a product line of Thiokol, which was the original builder of the ICBM stages, and later got merged with ATK and then with Orbital.  This stage then essentially has a Pegasus stuck on top of it (without the wings and tail), acting as the second through fourth stages, which are much skinnier than the bottom stage. So basically they’ve substituted a “stage zero” booster for the carrier airplane, and by doing so have roughly doubled the payload capacity relative to the Pegasus. The resulting vehicle has occasionally been mocked as a “Frankenstein rocket”, but there’s a great tradition of rockets pieced together from mismatched preexisting stages, especially in the early days. The Taurus’s commercial mission success rate has not been good. It recently had a hiatus of six years after a particularly embarrassing failure, and the new version they came up with in 2017 has been significantly revised. It was then that they dropped the Taurus name, and called it “Minotaur-C”, for Commercial. It has found very few customers under that name.

Two of the Taurus’s failures were not Orbital’s fault: it was eventually found that a supplier involved in making the fairings, Hydro Extrusion USA, had been falsifying their test results and delivering substandard junk. This resulted in criminal charges. One testing supervisor got jail time, and the company had to pay around $45 million in penalties.

Unlike the commercial version, the governmental Minotaurs have never failed — hence the use of the Minotaur brand for the revised Taurus.

Minotaur-C: mass 73 t, diam 2.4 m, thrust 1600 kN, imp 2.3 km/s, type S, payload 1.3 t (1.8%), cost $30M/t, record 12/0/3 (including IV and V — record of I is 12/0/0).