I have found a Chinese paper by someone in CALT that describes the design rationale of the next generation small launch vehicle, now known as CZ-6. It also gives a rough description of the different configurations considered. The first stage uses a 3.35 m diameter first stage, modified to hold only one YF-100 kerolox engine (as opposed to two of them in the common 3.35 m kerolox block), and holds 76 tonnes of propellant. The second stage is powered by a restartable 150 kN thrust kerolox engine (the YF-115) that holds 15.15 tonnes of propellant. The most unusual aspect, however, is the thrusters on the ACS of the first two stages and a third "trim stage": they all use thrusters powered by a mixture of kerosene and hydrogen peroxide! Specifically:
- the first stage uses four 1000N thrusters for roll control
- the second stage uses four 25N thrusters for roll control
- the trim stage is powered by four 1000N thrusters, along with eight 100N thrusters for attitude control
The basic parameters for the chosen configuration (type "C" in the paper) is given as follows:
Length: 29.237 m
Total mass at liftoff: 103.217 tonnes
Thrust to weight ratio at launch: 1.20
Maximum dynamic pressure: 22.3 kPa
Maximum axial acceleration: 5.0 g
Fairing diameter: 2.25 m / 2.6 m
Payload to 700 km SSO: 1080 kg (500 kg if only Chinese tracking stations are used)
Dry mass of the three stages combined: 9.02 tonnes
The paper also shows why the original configuration considered (the one using the 2.25 m diameter kerolox block, i.e. configuration "B" in the paper) was not chosen:
1. The rocket would be too long and thin for current facilities (Length to diameter ratio = 15.9), and launching large satellites or multiple satellites would be a PITA.
2. The maximum loads are rather high (T/W ratio = 1.459, MDP = 36.9 kPa), and would require measures to reduce the load on the payloads.
3. The maximum payload isn't that high (payload to 700 km SSO = 870 kg).