For the first time, both fuel tanks of rocket R-5 were integral. Experience gained from operating rockets R-1 and R-2, as well as analysis and experiments showed that evaporation of liquid oxygen while on a launch pad and during an ascent phase were not so sizable as it was previously thought and, with a proper re-supply of the oxygen tank at a launch pad, heat shield might no longer be needed. Further, such an approach became routine for a rocket of any design using liquid oxygen in the capacity of a propellant component.
The rocket R-5 engine was provided with a special extension nozzle that enabled to increase a flight range up to 1200 km. The pressurized instrumentation compartment was removed. All control system instruments, except for sensitive elements (gyroscopic devices and integrators) were housed in a compartment being a direct continuation of the aft compartment. The sensitive elements were accommodated far from the engine, in the inter-tank section on special brackets to avoid vibration effects. In addition to the autonomous control system, range radio control, cross range radio correction, and engine emergency shutdown systems were used for the first time. The tanks were provided with vortex-free fuel intake devices to decrease fuel remainders.

241x800 (20 794 bytes)		Principal characteristics of rocket R-5
		Maximum firing range, km Launch mass, kg Warhead mass, kg Propellants mass (liquid oxygen, ethyl alcohol, hydrogen peroxide, gas), kg PU ground thrust, kgf	1200 28570 1425 24370 43860

Aerodynamic and heat resistance appeared to be a rather large problem. The warhead, re-entering atmosphere at a velocity of above 3000 m/s, was exposed to high temperature loads. To protect the warhead shell, application specific coatings based on sublimated (evaporating) high enthalpy materials have been developed.
Prior to carry out flight tests at the 2 NII-88 affiliate division, firing bench tests of rocket R-5 were run. The purpose was to define an actual temperature of propellants in fuel tanks, verify the control system and engine automatics functionality, verify the engine firing timeline and record its actual performance data.
Three cycles of R-5 flight tests were planned of which the first and the second cycles were experimental and the third cycle included adjustment and qualification tests.
The first cycle of R-5 flight tests has been carried out in March - May, 1953. Eight launches have been performed: two launches - to a range of 270 km, five launches - to a range of 1200 km, and one launch - to a range of 550 km. Six of eight rockets reached the destination. The first successful launch to a maximum range took place on April 19, 1953.
While preparing for the second cycle of R-5 tests, a number of modifications were made to the rocket structure and control system.
The second cycle of R-5 tests has been run in October-December 1953. A launch range of all 7 rockets was 1185 km. One launch failed because of a damage in the onboard cabling that triggered the engine shutdown command and, consequently, resulted in the rocket undershoot.
The third cycle of R-5 flight tests took place in a period from August 1954 to February 1955. In total, 19 launches have been carried out: 5 adjustment launches, 10 qualification launches and, in addition, 4 adjustment launches were added because of failures to verify range radio control.
Rocket R-5 introduced a qualitatively new approach to designing ballistic rockets. With a 37% increase in the R-5 launch mass its firing range increased two times as compared to R-2, masses of fore bodies being practically equal. It was achieved mainly through increasing the engine specific impulse and sufficiently decreasing (by 25%) the rocket structure relative mass (without the warhead) that in many aspects demonstrated technological maturity of the rocket.