# A Brazilian Space Launch System for the Small Satellite Market
## 2 Methodology and Launch Vehicle Configuration
### Vehicle Configurations  
Concerning orbital stages, solid rocket motors have limited applications when multiple burns are necessary. Consequently, some configurations have a liquid propellant upper stage with re-ignition capability for multiple payload orbit insertion and de-orbiting operation. To speed up the development of the launch system, as well as to reduce overall costs, the upper stage was designed to rely on off-the-shelf components, mostly from the satellite industry. Therefore, we selected for the liquid upper stage the RD-843 motor from Yuzhnoye SDO, Ukraine. This engine is employed in the fourth stage (AVUM) of the VEGA launch vehicle. Table 1 presents the main characteristics of the RD-843 liquid engine [17]. We conducted a preliminary performance analysis considering six configurations for the small satellite launch system based on combinations of the S50 motor for lower stages and the S44 and RD-843 for the upper stages. From this set of candidates, we selected the best three configurations for further cost assessment analysis, namely:  
* Concept 1 (**C-1**)--this expendable launch system relies on adding two S-50 engines to the first stage of the basic VLM-1 configuration, We kept the S-50 and S-44 motor in the second and upper stages, respectively;
* Concept 2 (**C-2**)--is a three-stage (all serial) expendable launcher, in which three S-50 motors are combined into the first stage, one S-50 motor is used for the second stage and one RD-843 engine (2.5 kN) is employed for the upper stage;
* Concept 3 (**C-3**)--this expendable launch vehicle has three S-50 motors for the first stage, one S-50 motor for the second stage and a liquid upper stage comprised of four RD-843 engines. Figure 5 shows the vehicle concept number 3, in which the first stage is comprised of a cluster of three S-50 motors, another S-50 motor is employed in the second stage and a cluster of four RD-843 liquid rocket engines is used for the upper stage. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Mass** & **Thrust** & **Specific Impulse** & **Number of Burns** & **Operation Time** \\ \hline
16.5 kg & 2.5 kN & 315.5 s & 5 & 700 s \\ \hline \hline \end{tabular}
\end{table} 
Table 1: RD-843 main characteristics [17]. Table 2 presents relevant properties for each stage, as claimed by the _DBallistic_ model for performance predictions. The propellant mass and specific impulse necessary to model the S-50 and S-44 motors were taken from system requirement data documentation from the Brazilian Space Agency. On the C-1 configuration, the S-44 is used as the circularization motor and that stage is comprised of the motor and payload adapter masses. In Table 3, PM, PMF, and area refer to the total stage propellant mass, propellant mass fraction, and aerodynamic area, respectively. The propellant mass for the liquid upper stage (C-2 and C-3) was calculated based on the maximization of vehicle's \(\Delta V\). The liquid stage dry mass was inferred based on commercial components from geostationary satellites propulsion systems with a composite tube structure similar to a satellite's central tube, thus ensuring a short design to operation time. The mass of the fairing was also included to the dry mass of the third stage. The mass of the interstage linking the second and upper stage was included into the dry mass of the second stage. The first stage derived from the combination of three S-50 motors was modelled considering a dry mass equivalent to three S-50 motors plus and addition of 550 kg to account for the interstage, structural linkage and reinforcements. This modelling seems conservative for performance and cost estimation. Propellant mass fraction estimations were based on the adopted technology for the engines. The S-50 solid-fuel motor, for instance, is manufactured based on composite casing technology. From Table 2 it is possible to infer the gross lift-off weight (GLOW) of each configuration, without payload mass.