Krunichev’s Proton is a three-stage vehicle that can be used to put heavy payloads into low earth orbit or, more frequently, to boost a fourth stage and payload on a geosynchronous transfer orbit (GTO) mission. Proton can use either the RSC Energia Blok DM or the Krunichev Briz-M as a fourth stage. The new Proton-M, with updated electronics and improved first stage engines, replaces the older Proton-K model. A fully fueled Proton stands 61 meters tall and weighs nearly 700 metric tons.
The three core Proton stages burn hypergolic N2O4/UDMH. The first stage consists of a 20.2 meter long, 4.1 meter diameter central oxidizer tank surrounded by six, 1.7 meter diameter fuel tanks. Each outboard fuel tank carries one RD-253 (Proton K) or RD-275 (Proton M) engines. The six engines provide a total of more than 1,000 tons of thrust for about 120 seconds.
The 4.1 meter diameter second stage is powered by four gimbaled RD-210 engines that develop a total of 237 tons thrust for about 215 seconds. The 4.1 meter diameter third stage is powered by a single fixed RD-210 engine that produces 59 tons thrust for about 232 seconds and a four-nozzle vernier/steering engine that produces 25,827 pounds of vacuum thrust for about 247 seconds. Proton’s flight control system, mounted in the third stage, controls the vehicle during the first three stage burns.
Proton must fly one of three, fixed-ascent trajectories from Baikonur to reach a 200 km parking orbit with an inclination of either 51.6, 64.8 or 72.7 degrees. Launch trajectories are fixed by landing zones for the spent first stage, about 310 km from the Baikonur launch site, and the second stage and payload fairing, about 1,985 km from the launch site.
Typically, the second stage begins a “fire in the hole” ignition 122 seconds after liftoff while still attached to the first stage. After a 215 second burn, the Stage 3 verniers ignite, the second stage engines shut down, six solid second stage retro rockets fire to separate the second and thrid stages, and the third stage engine ignites. The payload fairing is jettisoned a few seconds later.
The third stage main engine shuts down 567 seconds after liftoff. Its verniers burn for another 10 seconds. 595 seconds after liftoff, the Stage 3 retro rockets fire to separate the stage from the upper stage/payload.
On most Proton K/DM missions, the third stage injects the upper stage and payload directly into a parking orbit. On Proton-M/Briz-M flights, the third stage does not reach orbital velocity. Instead, Briz-M performs a brief parking orbit injection burn.
Block DM
Proton’s RSC Energia Block DM fourth stage is derived from the Block D stage developed for the Soviet lunar landing program during the 1960s. The stage is powered by a restartable 11D58M (RD-58M) gimbaled main engine that burns liquid oxygen (LOX) and kerosene to deliver 8,5 tons of thrust. Two storable bipropellant (N2O4/UDMH) “SOZ”, or “micro”, thruster units located at the base of the stage provide three-axis stabilization during unpowered flight.
Block DM is built around a spherical LOX tank mounted above a toroidial (doughnut-shaped) kerosene tank. An equipment bay containing stage guidance, navigation, and control hardware is located above the LOX tank.
The main engine is mounted below, and partially nestled within the center of, the kerosene tank. A tubular truss structure ties the separate tanks and equipment bay together. A tapered aft shroud and a cylindrical forward shroud protect Block DM during ascent.
Several Block DM variants are currently in use. The Block DM-2, or 11S861, is the standard government version. It is powered by the RD-58M. The newer Block DM-2M (11S861-01) provides slightly better performance by burning synthetic kerosene fuel in an RD-58S engine. The Block DM-5, or 17S40, also uses the RD-58M engine, but it is designed to carry heavy payloads to low earth orbit. It has a stronger, heavier payload adapter and it carries less fuel than Block DM-2.
Block DM stage nomenclature got confusing when RSC Energia established a new identification system for commercial flights in 1996. Since then, commercial Block DM-2M stages have usually been identified as Block DM3 (usually for ILS missions) stages.
Briz-M
Krunichev’s Briz-M fourth stage is derived from the Briz-K stage flown on Rokot. It provides improved payload performance compared to the Blok DM series. Much of the performance gain comes from the use of a jettisonable toroidial propellant tank. The “drop tank” surrounds a core section, effectively a Briz-K, composed of propellant tanks, an avionics bay, and a propulsion system. A single, gimbaled R2000 19.62 kN thrust main engine powers the stage. It is augmented by four 394 N “impulse adjustment thrusters” and twelve 13.3 N attitude control thrusters. The main engine can be restarted up to eight times.
Breeze M uses a lower thrust engine than Block DM. As a result, it must perform at least two perigee burns, in place of a single Block DM perigee burn, to put payloads into GTO. Typically, the first burn raises apogee to 5,000-7,000 km. The second burn, one orbit and about 2.5 hours later, boosts apogee to GTO altitude (35,000 km). This second perigee burn is actually two burns conducted in succession, with the empty drop tank jettisonned in between. The final burn, at apogee about 5.2 hours later, raises perigee and lowers orbital inclination. Proton/Briz-M missions can last 9-10 hours, compared to 5.5-6.5 hours for Proton-K/Blok DM.
Also read: Pegasus – Space Launch Report
Launch Sites
Since the mid-1960s, Proton has flown only from Baikonur. Initially, the rocket lifted off from one of two launch pads (Pad 23 and 24) at Area 81. During the late 1970s and early 1980s, two new pads (39 and 40) entered service at Area 200. During the late 1990s, Area 81/Pad 24 was modified to support Proton M, but also continued to host Proton K. Area 200/Pad 39 began handling Proton M/Briz M flights in 2004. Area 81/Pad 23 was not used in 2006 or during the first half of 2007. Area 200/Pad 40 has been out of service since the early 1990s.
Like Soyuz, Proton and payload are integrated horizontally on a rail-transporter in a hanger. A few days before launch, the entire 61 meter long vehicle is rolled out horizontally to its austere launch pad where the rail-transporter erects the vehicle into a vertical position. A mobile service tower then partially encloses the vehicle until launch day. This flexible system supported a record 14 Proton launches in 2000.
ILS
Since 1995, Proton has flown commercial satellite missions for International Launch Services (ILS), an international consortium originally owned by Lockheed Martin, Krunichev, and RSC Energia. Lockheed Martin sold its ILS share to Space Transport Inc in 2006. Through ILS, Proton, long a government civil/military launcher, has steadily gained commercial market share. Since 1990, Proton has been one of the world’s most reliable high-mass GTO launchers. The Saturn I/IB class Proton launcher performed its 325th mission on April 9, 2007.
Vehicle Configurations
| LEO Payload (metric tons) 200 km x 51.6 deg | GTO Payload 1500 m/s from GEO* (metric tons) | Earth Escape Payload C3=0 (metric tons) | Configuration | LIftoff Height (meters) | Liftoff Mass (metric tons) | |
| Proton K | 19.76 t | 3 Stage Proton-K | 61 m | 669 t | ||
| Proton K/DM-2M | 4.9 t | 3 Stage Proton-K + Blok DM-2M | 61 m | 686 t | ||
| Proton M | 21.60 t | 3 Stage Proton-M | 56.2 m | 669 t | ||
| Proton M/Briz-M | 5.65 t | 5.65 t | 3 Stage Proton-M + Briz-M | 56.2 m | 691 t | |
| Proton M/Briz-M Enhanced | 6.3 t | 6.3 t | 3 Stage Proton-M Enhanced + Briz-M | 56.2 m | 691 t |
Vehicle Components
| Proton-K/M First Stage | Proton-K/M 2nd Stage | Proton-K/M 3rd Stage | Blok DM-2M 4th Stage | Briz-M 4th Stage | |
| Diameter (m) | 7.4 m | 4.1 m | 4.1 m | 3.7 m | 4.0 m |
| Length (m) | 20.2 m | m | m | 6.28 m | 2.61 m |
| Propellant Mass (tons) | 419.41 t | 156.11 t | 46.56 t | 15.05 t | 19.8 t |
| Total Mass (tons) | 450.41 t | 167.83 t | 50.75 t | 17.49 t | 22.17 t |
| Engine | RD-253/RD-275 | RD-210 | RD-210 | 11D58M | S5.98M |
| Engine Mfgr | Glushko | Kosberg | Kosberg | Energia | Isayev |
| Fuel | UDMH | UDMH | UDMH | Kerosene | UDMH |
| Oxidizer | N2O4 | N2O4 | N2O4 | LOX | N2O4 |
| Thrust (SL tons) | 970.5 t/1,016 t | ||||
| Thrust (Vac tons) | 1,070 t/1,120 t (avg) | 237 t | 62 t | 8.5 t | 2.0 t |
| ISP (SL sec) | 285 s | ||||
| ISP (Vac sec) | 316 s | 327 s | 327 s | 361 s | 326 s |
| Burn Time (sec) | 120 s | 215 s | 237 s | 680 s | 3200 s |
| No. Engines | 6 | 4 | 1 | 1 | 1 |
