ISRO- Vehicle Of Progress

ISRO crosses yet another milestone with the successful launch and return of a winged Reusable Launch Vehicle in a scaled-down configuration that flew in a hypersonic regime.

- R.Ramachandran AND T.S.Subramanian

Bringing down significantly the cost of access to space is a primary goal of space programmes around the world today. What this means, for example, is reducing the cost/kg of payload delivered when a launch vehicle is used to put a satellite into orbit. There are, of course, different options by which one can think of reducing this cost from the following basic considerations. Typically, the on-board propellant accounts for about 85 per cent of the mass and the rest is structural hardware. The payload fraction itself is quite small, ranging from 0.4 per cent to 1 per cent of the total mass depending upon the mission and the efficiency of the system. In terms of cost, however, the hardware accounts for about 80 per cent of the launch cost. The cost of the fuel itself is negligible.

Conceptually, therefore, there are three strategies to reduce the cost/kg of payload mass: (i) improve the payload fraction by adopting newer technologies and improving the overall efficiency of the system, including increasing the thrust of the vehicle by more efficient liquid fuel engines, such as semi-cryogenic and cryogenic engines; (ii) recover the hardware and reuse for multiple launches; and (iii) reduce the initial propellant loading by adopting newer combustion modes such as air breathing ramjet / scramjet propulsions, and any suitable combination thereof depending on the mission at hand.