Rockets of Today

SSLV — India, 2022

The Indian space agency’s PSLV has been a considerable success, but clearly they have to bring launch prices down. Although they are working on a reusable launch vehicle, for the short term the way to do it is the way everyone else has been doing it: by building a cheap solid rocket with minimal capacity.

They’re talking up plans to have fifty or more launches a year, bringing in lots of revenue. But given the large number of direct competitors this rocket will have, especially in China, I am doubtful of it finding that much business. One thing they’ve done to add potential customers is make a deal to launch it from South Korea’s Naro facility.

SSLV stands for Small Satellite Launch Vehicle, and they originally said it would cost a tenth of what the PSLV costs, despite its not being all that tiny. They say, for instance, that it could be prepped and stacked by six people in a week, whereas the PSLV takes hundreds of people. Despite this, they’re now naming a cost around a quarter of the PSLV’s, so not much better per ton.

The rocket itself is as uninteresting as most of its small solid peers. The bottom stage is called the S85, which makes it smaller than the core booster of the PSLV, but not a lot smaller. It has a segmented body, presumably made of steel. The second stage is the S7, which is the third stage on the PSLV, or a minor variation of it. Atop that goes the S4, which is similar but shortened. Finally, a liquid-fueled kick stage is used for orbital trimming. It has open mesh interstages like an old Russian rocket — a feature which seems pointless when solid fuel is used, as its main benefit is to allow ignition of liquid stages while under thrust, obviating the need for separate ullage motors.

Detailed specs are still a bit scant. The most interesting bit is the kick stage, or Velocity Trimming Module, which has sixteen tiny thrusters and no main engine. It burns monomethylhydrazine.

The rocket has been subjected to extensive delays. First, all work on it was paused so that ISRO could concentrate on their Chandrayaan 2 moon shot (which crashed on the lunar surface, like Israel’s Beresheet). Then the following year, the whole space center pretty much shut down due to covid-19. It finally got to fly in August 2022, and it did get to orbit, but not to a usable orbit. The guidance controller got a bit disoriented by the unexpectedly sharp jolt of stage separation, and the payload soon ended up back in the atmosphere. Six months later, it flew successfully.

SSLV: mass 120 t, diam 2.02 m, thrust 2.5 kN, imp unknown, solid fuel, payload 0.5 t (0.4%), cost ~$10M/t, record 1/0/1 through 2023.