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The Buran !
So just how do the world's two shuttle systems go head to head, here’s a look at some of the improvemnets added to the Buran system in light of being built after the US STS...
At first glance, it would appear as if the U.S Shuttle and Buran-Energia are quite similar, and in many ways, they are. The Buran was, after all, based on the American space shuttle design. On a purely visual level the two shuttles look almost identical, their sizes are little more than centimetres apart.
Numerous important differences do, however, exist underneath the surface. Key aspects of the American design were rejected by Russian engineers, and here we will highlight some of the features that we feel illustrate the superior capability of the Buran-Energia system.
A critical difference between the two shuttle designs is in their rocket systems. The Energia is a monster of a rocket, with significantly more thrust that the American shuttle central fuel tank and solid rocket boosters (SRB's). The Energia is a dedicated heavy lift rocket that is capable of sending up to a staggering 175 tonnes into orbit! (with eight strap on boosters and Energia-M upper stage), or 90-100 tonnes in standard mode. To put that into perspective the U.S shuttle and Protons are assembling the International Space Station Alpha in 20-30 tonne pieces (the limit that it can take up). Energia could take up easily over 100 tonnes in one go, because it doesn’t have to take up the Buran shuttle, the shuttle is simply one of its cargoes!
There are also significant differences in how the two rocket systems get their respective cargoes into orbit. The U.S shuttle's central tank is not a rocket, but simply, as the name implies, a tank. The U.S shuttle system must rely on the side booster rockets as well as the shuttle's own rockets to take it to a sufficiently high orbit, without the shuttle, the system won't get very far off the ground.
The Energia, on the other hand, serves as a launch platform for the Buran but is a fully fledged heavy lift rocket system in its own right, capable of taking up varied cargos as far as the Moon or even potentially Mars! As many as eight Zenit boosters can be strapped on it to give it a lifting power that far exceeds its nearest equivalent.
Another important difference is that the Buran-Energia is designed as a fully reusable shuttle system, that includes the four side 'Zenit' boosters and the main huge 'Energia' core super booster (Energia-T). The U.S shuttle system, on the other hand, is only semi reusable. Every time a U.S shuttle is launched a new central fuel tank has to be constructed, an extremely expensive process. In addition the SRB's, often described as fully reusable are in fact far from it, they need to be heavily refurbished after each launch. The Buran does not suffer from such problems. The Zenit boosters that strap on to the Energia core rocket are equipped with large parachute/retro rocket soft landing systems. The Energia core booster itself is designed to use such a system. This allows Energia and Zenit rockets to be recovered, refuelled, and re used at least ten times. It it worth noting, however, that the first flight of Buran-Energia in space did not take place with recoverable side or core booster rockets, but this was still in the development phase of the shuttle's life. Future launches would feature the fully recoverable Energia system, which of course, never got to occur as the program was suspended.
One important difference that the Cosmonauts would no doubt have appreciated was that the Energia rocket system is powered solely by liquid propellant, both in the core booster and in the side booster rockets. Liquid propellant is a safe and effective form of rocket propulsion. It is also quite expensive. The Amercian shuttle does not have liquid propellant in its solid rockets boosters (SRB's) as a result of budget cuts in the 1970's. As any American Astronaut will tell you, SRB's are dangerous, little more then controlled explosions. The famous U.S astronaut Story Musgrave, does not welcome being in close proxmity to an SRB, he once commented "The very concept of SRB's that large.... (his voice trailed off) ...A launch is incredibly frightening, probably the most dangerous part of the mission... ...On subsequent ones (launches) I have become more and more scared". The simple facts are that a fault in a SRB means instant destruction of the shuttle. It was a faulty SRB O-ring seal on the shuttle Challenger that led to its unfortunate destruction. Buran-Energia does not share this problem. As an added safety feature, Buran was fitted with ejection seats for her crew. Remarkably, these high-tech seats can withstand Mach 4+ blow outs. Thermal protection was also considerably better on the Buran, allowing for safer reentries to Earth’s atmosphere. Jet engines for the Buran shuttle were also to be installed, so as to give a little added safety to the shuttle on landing, as most people know shuttle tend to glide into landing like bricks, a few engines up back certainly will be appreciated if you’re landing in adverse weather conditions.
Another notable difference between the Buran Shuttle and the U.S design is that Buran, when separated from Energia, does not have any real engines in the sense that the American shuttle does. It simply does not need them. The Energia rocket which carries the Buran into orbit is so powerful that the Buran does not need its own propulsion. The Energia can take the Buran as high as it likes. This is in stark contrast to the American shuttle design where after the core booster separates the U.S shuttle must still propel itself forward if it is to reach significant altitude.
The lack of a need for engines also allows the Buran to have a significantly longer cargo bay, therefore allowing of the deployment of larger and heavier cargo.
The Buran shuttle itself, otherwise, is quite similar to the U.S shuttle, it is, however, more advanced in the sense that unlike the U.S shuttle it can be piloted unmanned solely by computer, completing even complex two week missions with no-one on board.
To summarise... Buran-Energia was in many ways an improvement on the US Shuttle system, with a much more flexible design, even if sadly, it is not the system that is currently in operation.