|UR-700M - |
Credit: Mark Wade. 6,911 bytes. 73 x 480 pixels.
By the middle of 1969, NASA was pressing for funding for a manned expedition to Mars. On 30 June 1969 he Soviet Ministry of Defence authorised preparation of Soviet draft projects for a manned Mars expedition. Code named Aelita, the TTZ specification called for a launch vehicle with a low earth orbit payload of 200 to 250 tonnes to be available by 1976. Chelomeiís response used a modular approach to the launch vehicle design in order to achieve payloads of 300 to 800 tonnes. This would allow an expedition to Mars using a single docking in low earth orbit.
The proposed UR-700M launch vehicle had a gross lift-off mass of 16,000 tonnes and could deliver 750 tonnes to a 250 km, 51.6 degree orbit. It consisted of three stages: Stage 1 and 2 used Lox/Kerosene propellants, and stage 3 Lox/LH2. As in the UR-700, all the engines of Stage 1 and Stage 2 operated at lift-off, but the engines of the second stage were fed from propellant tanks in the first stage. The vehicle consisted of five 9 m diameter first stage blocks with a dry mass of 750 tonnes, three second stage blocks (two of 9 m diameter flanking a 12.5 m diameter core block) with a dry mass of 500 tonnes, and a 12.5 m diameter, 200 tonne empty mass third stage. Each of the outer blocks had 4 x 600 tf engines by KBEM (two 300 tf chambers per engine), while the 12.5 m diameter core block had a total of 6 x 600 tf engines. The third stage had 6 x NK-35 engines of 200 tf each.
The UR-700M/LK-700 advanced project was reviewed by the expert commission in 1972. The commission concluded the Mars project - and the UR-700M booster - were beyond the technical and economical capabilities of the Soviet Union and should be shelved indefinitely.
In 1962 Vladimir Chelomei proposed a family of modular launch vehicles. The UR-700 was designed for direct manned flight to the surface of the moon. While approval to proceed with development of the UR-500 came in April 1962, no such go-ahead was received for the UR-700. Studies continued however, and report index number 4855CC by TsNIIMASH in 1966 showed that any development of improved versions of the N1 would be practically equivalent to design and qualification of a new rocket, while the UR-700 modular approach allowed a range of payloads without requalification. UR-700 derivatives could better support the DLB lunar base, Venus/Mars manned flybys and Mars landing expeditions. Development of the UR-700 was approved on 17 September 1967. However no go-ahead to proceed past the design phase was forthcoming in 1968.
By January 1969, Chelomei was proposing the UR-900 for the Mars expedition. Chertok asked Chelomei what would happen if, God forbid, such a booster exploded on the launch pad. Wouldn't the entire launch complex be rendered a dead zone for 18 to 20 years? Chelomei's reply was that it wouldn't explode, since Glushko's engines were reliable and didn't fail. Aside from that, these propellants had been used in hundreds of military rockets, deployed in silos, aboard ships and submarines, with no problem. Fear of these propellants was irrational. Related propellants were used by the Americans on the Apollo manned spacecraft.
Less than three months later, on 2 April 1969, the unimaginable happened. A Proton rocket, one tenth the size of the planned UR-900, was launched in an attempt to send an unmanned probe to Mars. The leadership of the Soviet Rocket Forces and most of the Chief Designers were present for the event. The Proton rocket lifted off, but one engine failed. The vehicle flew at an altitude of 50 m horizontally, finally exploding only a few dozen metres from the launch pad, spraying the whole complex with poisonous propellants that were quickly spread by the wind. Everyone took off in their autos to escape, but which direction to go? Finally it was decided that the launch point was the safest, but this proved to be even more dangerous - the second stage was still intact and liable to explode. The contamination was so bad that there was no way to clean up - the only possibility was just had to wait for rain to wash it away. This didn't happen until the Mars 1969 launch window was closed, so the first such probe was not put into space until 1971.
This accident seems to have made a powerful impression on the military, and plans for a new generation of space launchers drawn up in the early 1970's specified use of non-toxic liquid oxygen and kerosene propellants. This also forced Chelomei to specify these propellants in the redesignated UR-700M for the Mars expedition.
By the middle of 1969, in the post-Apollo moon landing euphoria, NASA was pressing for funding for a manned expedition to Mars. Ministry of Defence decree 232 of 30 June 1969 authorised preparation of Soviet draft projects for a manned Mars expedition. Code named Aelita, the TTZ specification for the expedition was prepared by TsNIIMASH and NIITI. The TTZ called for a launch vehicle with a low earth orbit payload of 200 to 250 tonnes to be available by 1976. This vehicle would be used to support a Soviet lunar base, heavy military and civilian space stations, and a Mars expedition spacecraft of 1,500 tonnes mass.
Analysis of the requirement by Chelomei indicated a larger launch vehicle than that required by the TTZ would be optimum. Opportunities for launches to Mars had limited launch windows at two year intervals. The combined proability of successfully launching, docking, and assembling a half dozen payloads in low earth orbit was relatively low. The optimum chance for mission success was to use no more than one or two dockings in earth orbit. (NASA came to a similar conclusion in the early 1960's, leading to the Nova launch vehicle studies). Chelomei used a modular approach to the launch vehicle design in order to achieve payloads of 300 to 800 tonnes. By the advanced project stage the MK-700 Mars spacecraft assembly sequence had been reduced to two variants:
Unit p/ya A-1233 of TsKBM determined that it would be possible to reduce the mass of the Mars spacecraft to 900 to 1,000 tonnes. This would allow the Variant 2 booster to be used with only one docking.
The design evolved considerably over the next three years. The preliminary draft project utilised the following design principles of the UR-700M were:
The UR-700M/LK-700 advanced project was reviewed by the expert commission in 1972. Their conclusions were:
LEO Payload: 750,000 kg. to: 200 km Orbit. at: 51.0 degrees. Liftoff Thrust: 20,400,000 kgf. Total Mass: 16,000,000 kg. Core Diameter: 31.0 m. Total Length: 175.0 m.
Ministry of General Machine Building (MOM) Decree 232 'On start of work on the UR-700M rocket' was issued. The decree allowed development of an advanced project for a manned Mars expedition using the UR-700M booster and MK-700 spacecraft. The TTZ specification document was written by the TsNIIMASH and NIITI institutes, and the project was given the code name 'Aelita'.
Chelomei's preliminary draft project for the UR-700M launch vehicle and LK-700 spacecraft was reviewed by a government expert commission. Based on the decades worth of development and tens of billions or roubles required to realise the project, the state commission recommended that further work on manned Mars expeditions be deferred indefinitely.