Proton (rocket family): Difference between revisions

Revision as of 06:27, 8 July 2007

Revision as of 19:03, 8 July 2007

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==Proton 8K82K==

The ([[GRAU|GRAU index]]) 8K82K version is now usually called "Proton K". It is fuelled by [[UDMH|unsymmetrical dimethyl hydrazine]] and [[nitrogen tetroxide]]. These are [[hypergolic]] fuels which burn on contact, avoiding the need for an ignition system, and can be stored at ambient temperatures. This avoids the need for low-temperature-tolerant components, and allows the rocket to sit on the pad indefinitely (the only other rockets with such capability were the U.S. [[Titan II]], [[Titan III]], and [[Titan IV]] rockets). In contrast, [[cryogenic fuel|cryogenic fuels]] need periodic topping-up of propellants as they boil off. Hypergols are, however, very [[corrosive]] and [[toxic]] fuels, requiring special handling by highly trained labor. When the spent first and second stages impact downrange, Russia must pay for cleanup of the residual fuel.

Note that the six structures around the base of the Proton are not strap on booster rockets, and do not detach from the core structure. There is a central oxidizer tank, and the six units are outrigger fuel tanks. This entire assembly forms the [[Multistage rocket | first stage]], which separates as one piece from the second stage at the lattice structure. Outrigger tanks reduce sloshing, compared to the short, wide fuel and oxidizer tanks that would have been used in a standard, tandem configuration. They may also be cheaper to fabricate. They do however raise the specter of uneven fuel consumption and resulting flight instability. (The Titan rockets avoided this by having the fuel and oxidizer tanks located in the body itself. Thus, unlike the Proton, the Titan II and III rockets can be flown with or without solid boosters).)

The first stage uses six RD-253 engines, designed by [[Valentin Glushko]]. RD-253 is a single chamber engine and uses the highly efficient staged combustion cycle. First-stage guidance was open-loop. Though this method is quite simple, it required significant amounts of propellant to be held in reserve. This reduces payload.

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The second stage ignites while still attached to the first stage (a "fire in the hole" event, not done by the Titans, as they required in-flight staging, then ignition). Exhaust gases escape through the lattice. The forward dome of the first-stage oxidizer tank is insulated to retain integrity until stage separation.

The RD-0210 engine of the third stage consists of a main engine, and four vernier nozzles with common systems. The main engine does not [[gimbal]]; the verniers provide steering, and also act as separation aids and [[Ullage_%28rocketry%29|ullage rockets(rocketry)|ullage]]. rockets. Ducts are built into the structure to channel vernier exhaust before stage separation. The stage's guidance electronics are also in charge of first- and second-stage flight.

The fourth stage camehas come in multiple variants, depending on the mission. The simplest, Blok D, was used for interplanetary missions. Blok D had no guidance module, depending on the probe to control flight. Three different Blok DM versions (DM, DM2, and DM-2M) were for high Earth orbits. (Low-Earth orbits often skipped a fourth stage entirely, hence the third stage's self-contained guidance capability.) The Blok D/DM were unusual in that the fuel was stored in a toroidal tank, around the engine and behind the conventional oxidizer tank.

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