The Soviet Union’s Buran Orbiter - by Andrea
Buran grew out of the Soviet Union´s need to respond to the reusable spacecraft US started building in 1972, mainly for military missions, and the USSR felt the need to respond with a comparable craft to maintain a parity.
The Soviet Union built its own Orbiter, that was known as Buran ("snowstorm" in Russian) and, even if only the first built space-ready vehicle was named this way, the entire project was known as Buran.
The goals of the Buran project:
- To prevent the US gaining military supremacy in space
- To operate research for defence, science and the economy
- To carry out military research and experiments in space
- To deliver to orbit and return to Earth spacecraft, cosmonauts, and supplies
- To deliver a 30 ton payload to orbit, followed by seven days of orbital operations and return of a 20 ton payload to Earth
- To exploit the technology developed for the American Space Shuttle in order to enhance Soviet space technology capability
The last one was of particular interest. The Soviets attempted to build an equivalent to the Saturn V (Apollo program), but the N1 Soviet rocket was a failure, causing fear that the USSR would be left behind by the US in heavy rocket technology. The Soviet solution was to copy as much of the American Shuttle design as possible, in order to save a lot of money and time. But they modified the American project, where necessary, to take advantage of Soviet capabilities and to substitute technologies not available in the USSR.
For example, the Soviets had no experience building large solid rocket motors like those being developed as reusable boosters for the American Shuttle. On the other hand, they had a large liquid oxygen and kerosene engine under development, usable as an equivalent booster rocket. The Soviets also had little experience with cryogenic propellants, like those to be used in the main engines on the Shuttle, and lacked the ability to make such engines reusable.
|The Energia complex had a total of 20 engines!|
|Mass of Energia, t||2266.6|
|Mass of 1st stage, t||1490.4|
|Mass of 2nd stage, t||776.2|
|1st stage engine (RD-170) thrust, t||740|
|2nd stage engine (RD-120) thrust, t||190|
|1st stage height, m||39.46|
|1st stage diameter, m||3.92|
|2nd stage height, m||58.765|
|2nd stage diameter, m||7.75|
These considerations led to a number of key decisions in the design. For example, the lack of reusable rocket engines meant no need to carry the main engines aboard the Buran. So the booster was composed of a large central core called the Energia rocket, that took the place occupied by the external fuel tank on the US Shuttle.
This central core was surrounded by four liquid rocket strap-on boosters similar to the two solid rocket boosters used in the American design. Unlike the US Shuttle, this basic core and strap-on system could also be used as an independent rocket.
The Energia core was a modular design that could be equipped with one to four rocket engines and from two to eight strap-on boosters. The Energia could also be fitted with different payload capsules permitting great flexibility in the launch configuration. The Buran was just one of several payload options that could be attached to the Energia core.
The Buran was externally very similar to the American Shuttle, but with many differences. Although Soviet engineers studied a number of innovative lifting body configurations for the reusable spacecraft, none appeared to be superior to the shape chosen by the Americans for theirs. The Soviets added a few changes of their own, however.
Buran versus the US Shuttle
The main differences between the Buran and Shuttle orbiters are the following ones:
- The automatic landing of Buran from orbit onto aerodrome
- The absence of a main rocket engine on the orbiter. The main engine was placed onto a central block of the carrier-rocket Energia, which is able to launch into an orbit 120 tonne of payload compared to the 30 tonne of the Space Shuttle
- The high lift-drag ratio of Buran is 6.5 against 5.5 for the Space Shuttle
- Buran was capable of returning 20 tonne of payload compared to 15 tonne for the Shuttle - from orbit to aerodrome
- The cutting lay-out pattern of thermal protection tiles of Buran is optimal, the longitudinal slits of tile belts are orthogonal to the flow line. Sharp angles of tiles are absent. The tile belts of Burans fuselage and fin have an optimal position
|The Shuttle and Buran Orbiters comparison|
Most notably, removing the propulsion system from Buran allowed it to carry a larger payload of 30 tonne into orbit, compared to the 25-tonne maximum of the US Shuttle. This is the reason for the big difference in the shapes of the aft fuselages. The landing weight was similarly increased to 20 tonbe from the 15-tonne limit for the American orbiter.
The general layout of Buran was very similar to that of the Shuttle and consisted of a long, cylindrically shaped fuselage attached to a low-mounted double delta wing. A two-deck crew cabin at the forward end of the fuselage contained the flight controls on the upper deck and living space below.
Compared to the American Shuttle, maximum crew size was increased from seven to ten with room for four cosmonauts provided on the main deck and the remaining six crew on the lower deck.
Aft of the cabin was a large payload bay capable of carrying docking modules, a manipulator arm, and payload containers similar to those of the American Shuttle. Also like the US orbiter, the external surface of the Buran was covered with 38,000 thermal protection tiles and carbon material to survive the heat of re-entry.
However, the Soviets believed that the orientation selected for the tiles was a more optimized configuration than that used by the US. And the maximum temperatures on Buran during re-entry were foreseen as lower than the Shuttle ones.
|Buran at lift-off|
As the overall configuration of the Buran was finalized, the Soviets constructed a number of test sub-scale models, five full-scale mock-ups and three structural test vehicles used to investigate a variety of manufacturing, assembly, and flying quality characteristics as well as handling procedures.
The information gained using these test vehicles made a success of the first flights of the Energia and Buran in the late 1980s.The Energia flew its first operational mission on May 11, 1987, and the launch vehicle performed flawlessly. This success spurred the Soviets to attempt the first flight of the complete Buran-Energia system the following year.
The launch occurred at 0600 on the morning of 15 November 1988 from the Baikonur Cosmodrome, in what is now Kazakhstan.
Unlike American Shuttle missions, this flight was conducted without a single human aboard the vehicle. The first mission was launched unmanned since the life support system was still not certified or fully installed and software for cockpit displays was incomplete.
Moreover, the primary goal of the flight was to test the automated launch, orbital maneuvering, and landing systems developed for the orbiter. It was considered unnecessary to risk a human crew on a shakedown flight.
|Comparing the vehicles|
|Payload at H=200km|
|Overall length, m||36.37||37.23|
|Fuselage width, m||5.5||6.91|
|Height from the ground, m||16.35||17.27|
|Payload bay length, m||18.55||18.3|
|Payload bay diameter, m||4.7||4.6|
The Buran orbital flight
Though the first flight occurred more than four years behind schedule, the mission was a complete success.
The automated launch sequence performs flawlessly, and at 6h00 a.m. Moscow time the Buran-Energia take off from the launching pad.
At 6h08 Buran and Energia separate, Buran begins its first autonomous flight. Altitude is almost 150 km and as planned by the flight program, piloting is made automatically and the Energia booster lifts the vehicle into a temporary orbit before the Buran separates as designed.
It then boosts itself to a higher orbit of 240-250 km, to complete two orbits around the Earth. After 1 h 30 min of flight the on-board computer sends the orders and transmits the operation parameters for slowing down to prepare for re-entry, and Buran automatically fires its retrorockets to begin the descent back into the atmosphere.
The data about wind speed and direction are downloaded and the shuttle stabilized, the tail ahead. The impulse of braking is given at 8h20 a.m. and 30 minutes later it comes in contact with the dense layers of the atmosphere. During its descent of 100 km the control system turnes the shuttle over once again to present the nose ahead. At 8h53 and 90 km of altitude, radio connection cuts off because of the plasma that surrounds the shuttle.
At 9h11 and an altitude of 50 km, the Buran is still 550 km from the aerodrome and, in spite of its speed decreasing, it is 10 times higher than the speed of sound. Now only 10 minutes remain before landing.
At 9 h 24 min 42 s a.m., exactly 206 minutes into the mission, only one second earlier than the flight plan, the shuttle smoothly touches the landing strip at Baikonur - and after a small race, stops at 9 h 25 min 24 seconds a.m.
|Buran immediately after its stop on Baikonur runway after the successful orbital flight|
Buran lost only five of its 38,000 thermal tiles over the course of the flight. Its unmanned flight marked the first time in history that a spacecraft of such size and complexity was launched, completed maneuvers in orbit, re-entered the atmosphere, and made a precise and elegant landing under completely automatic control.
In addition to Buran the Soviet program planned to build four additional orbiters. Work had begun on all four but none were completed before the fall of the Soviet Union.
Unfortunately, the ambitious plans to further develop the Buran and her sisters for a variety of military and scientific applications were not to be. Funding for the program was slashed after the first flight and further work had essentially stopped even before the collapse of the Soviet Union.
Buran never flew again, and though never officially cancelled, President Boris Yeltsin finally cut off funding in 1993.The ultimate failure of the Buran program was due to the massive costs - estimated to between 14.5 and 20 billion Rubles. This burden was so enormous and put such a strain on the national economy that it was likely a contributing factor to the demise of the Soviet Union itself.
The end of the Buran project
On 12 May 2002, most of the roof of the Baikonur enormous Site 112, the hangar where the Buran orbiter and all remaining Energia boosters were being stored, collapsed under the weight of snow and strong winds, killing eight workers and destroying the only Buran that had tasted space.
|Buran after the hangar collapse|
|The end - as a fight simulator in Gorky Park|
The second shuttle (named Ptichka), at least 95% complete, is still stored in the MIK Building at the Baikonur Cosmodrome in Kazakhstan.
The third, (unnamed) shuttle remained at the Tushino factory in Moscow where it was being assembled until 2004, when it was sold to the Auto & Technik Museum in Sinsheim, Germany.
The fourth (unnamed) one moved outdoors of the Tushino factory where it was being assembled. Stripped components like thermal tiles have been sold over the internet.
One of the training vessels was brought to Moscow from Baikonur and leased to a private company in 1995. Installed in the Gorky Park, it was converted into a flight simulator with 30 movable seats inside, capable of giving the illusion of weightlessness, and accompanied by a cinema screen showing Buran's only launch. Actually it´s abandoned.
This is the inglorious end of an ambitious project, that could give an enormous impulse to the space exploration and to the human activities on board of the ISS.