Baikal Reusable Booster

Vladimir KIRILLOV

At the 44^th international aerospace show in Le Bourget on June 16-23, 2001 the Khrunichev State Research and Production Space Center (the Khrunichev Center) presented its promis­ing Baikal first stage reusable booster (RB) for all azimuthal launch vehicles (LV) of the An­gara-B family. Baikal was designed at Molniya Research and Industrial Corporation (NPO Molniya) at orders from the Khrunichev Center. The project of the light all azimuthal Angara A1-V LV with the Baikal RB as its first stage passed approval at the Khrunichev Center on November 19, 1999. The Baikal demonstrated in Le Bourget in 2001 was a full-size engineering mock-up.

Work on the project began practically simulta­neously with the development of the Angara family of expendable LV. However, the Khrun­ichev Center failed to win government funding for the program, therefore it had to finance the project solely at the expense of its own commer­cial operations.

Experts from the Khrunichev Center believe the concept of a two-stage launch vehicle with a re­usable “atmospheric” first stage can guarantee flexibility in using various “space” stages. Space shuttles can also be among them, of course. However, a shuttle will have a much smaller size and weight (including the weight of its thermal protection and undercarriage) than a one stage reusable spaceship having the same orbiting and re-entry payload capacities. Conse­quently, a two-stage reusable space system will have higher technical indicators. This in its turn should affect the economic indicators that de­pend on the correlation between the payload weight and the weight of the injection system (the latter is significantly smaller in a two stage system). As for the total design and operational costs, the development of a system component by component may prove much less expensive than bringing a bigger and more complicated single stage spacecraft to operating condition. The only additional operation – staging – is well-developed in world practice and should not require significant spending.

A reusable “atmospheric” first stage for inject­ing singular payloads may be applied not only in two-stage injection systems. A combination of the ultimate payload with expendable upper stages and boosters that may be part of launch vehicles of any class can be a payload for a re­usable first stage. If the modular principle of forming reusable first stages (module stages) is applied, it is even possible to combine such re­usable modules with expendable first stages launched from the surface together.

It is this idea of applying reusable module stages that lies at the heart of the advanced concepts that the Khrunichev Center is cur­rently working on together with NPO Molniya in the framework of the Baikal project. Such module stages having a rocket engine for launch and boost, a fly-back jet engine, a tilting wing, aerodynamic control equipment, fly-back and landing gear are meant to be used both as first stages of light LV and as clusters or mounted boosters in medium and heavy LV.

The distinctive feature of Baikal is that it guar­antees not only the landing of the booster but also it return to the launch site thanks to its fly-back equipment. This equipment includes a fly-back engine and control system developed for the Buran spaceship. Designers estimate that its combination with Angara family LV will al­low cutting expenses on the delivery of payloads to orbit in 2-3 times.

The booster body comprises the nose, tank and tail sections. The nose section carries the fly-back turbojet engine (TJE) and altitude-control engines for the extra-atmospheric part of the flight. The liquid oxygen tank is installed in the front part of the tank section and the kerosene tank in its rear. Kerosene is used as a propellant both by the main rocket engine and the TJE during the flight to the landing site. The tanks are fully identical to those of the first stage of the Angara-1.2 LV. They are connected by a section containing the booster’s control and telemetric systems. The tail section contains the main liquid fuel rocket engine (LFRE) RD-191M and altitude-control engines.

Baikal RB has the aerodynamic configuration of a high-wing plane with a tiltable straight wing attached to the section between the two fuel tanks on the top of the fuselage body. The leading edge of the wing will be made of heat-resistant composite material.

The mock-up demonstrated at the air show in Le Bourget was equipped with the RD-191M rocket engine and RD-33 TJE currently applied on the MiG-29 fighter.

The single-chamber RD-191M main rocket en­gine designed at the Glushko Research and Pro­duction Association for Power Engineering weighs 2.2 tons and runs on kerosene and liquid oxygen. Its thrust at sea level is 196 tons, spe­cific impetus at sea level - 309 sec and in zero gravity - 337.5 sec. It is attached to the tail end of the booster in gimbal mount with a swinging angle of ±8° for pitching and yawing control.

The RD-33 fly-back jet engine designed at Kli­mov Corporation (St. Petersburg) in 1981 has a thrust of 81.4 Kn and weight of 1.05 tons. Its dimensions are: length – 4.3 m, width – 2 m, height - 1.1 m. The parameters of its cruising mode are: altitude – 11 km with a speed of speed - 0.8 M. In this mode the specific fuel consumption is 0.098 k/H an hour. The engine is equipped with safety and early defect detec­tion systems.

Under the Baikal project the RB may also be equipped with the RD-35 engine developed for the Yak-130 trainer aircraft.

The undercarriage of the booster is in fact a modified undercarriage of the Su-17 ground-at­tack aircraft.  The front strut is located in the nose section of the RB and the two rear ones in the section between tanks.

The designers of Baikal currently plan to use each booster for 25 launches but in the future intend to raise the number to 200.

Parameters of Baikal RB:

The Baikal mock-up shown at Le Bourget will later be used for statical strength and other ground tests. A spokesman for the Khrunichev Center has said that several Baikals are under work for flight tests. However, according to un­official statements by other Khrunichev Center representatives, there still is a long way to the production of models for captive tests, while the mock-up demonstrated at Le Bourget was made in haste and differs greatly in appearance and design from the Baikal that will actually be launched from Plesetsk cosmodrome.

The RB flight tests will be held in several stages. At the first the M-4 (Bison) strategic bomber is expected to be used and Baikal will be attached to its fuselage. After the bomber takes off and climbs the RB will separate from the bomber and land independently. Later Bai­kal will be launched from the Angara LV launch pad without the second stage. At the third stage of tests a regular Angara A1-V LV will be launched: Baikal plus the second stage of Angara-1.2 LV (I block). The possibility of testing Baikal with a lighter stage of the Rokot LV - the Briz-KM booster is also being consid­ered.

The flight of the Angara A-1V LV will have the following stages (T - moment of time, H - flight altitude, q_max  - maximum dynamic head, V_land - landing speed, L_land - landing run):

·   Take-off (T=0 sec);

·   Maximum dynamic head (T=80 sec, H=9.6 km, V=316 m/sec, q_max=2200 kg/m²);

·   Staging (T=180 sec, H=60.7 km, V=2220 m/sec);

·   Head fairing separation (T=220 sec, H=86.8 km, V=2424 m/sec);

·   Payload separation (T=500 sec, H=200.0 km, V=7783 m/sec);

·   Extra-atmospheric RB flight (T=260 sec, H=87.5 km, V=2081 m/sec);

·   Atmosphere re-entry (T=340 sec, H=58.0 km, V=2151 m/sec);

·   Atmospheric descent and return turn (T=640 sec, H=10.6 km, V=150 m/sec);

·   TJE starting, back flight (T=960 sec, H=4.9 km, V=150 m/sec);

·   Descent, landing approach (H=1.0 km, V=107 m/sec);

·   Airdrome landing (T=4000 sec, V_land= 280 km/h, L_land= 1200 m).

The wing tilts during the extra-atmospheric part of the flight. Before re-entry in the atmosphere the stage turns with its upper part where the wing attachment fin is located in the direction of the flow to guarantee a more effective use of the aerodynamic controls attached to the tail section. The incoming flow load presses it to, not from the body, unlike a conventional air­craft.

At the altitude of 30 km the stage experiences maximum dynamic head of q_max=4750 kg/m² at the speed of 6.4 M. At that moment the stage is exposed to transverse g-load of n_y=4.0. After passing the maximum dynamic head zone the stage makes a 180° banked turn. The tilting wing turns upward and undercarriage down­ward. When velocity drops below the speed of sound the turbojet engine is started. Baikal will independently enter the airdrome zone and land using its navigation system and avionics.

Parameters of Angara A1-V LV with Baikal RB

Launch weight, tons	168.9
Payload injected in lower circular orbit  (H=200 km, i=90°), tons	1.9
Propellant weight:
First stage, tons	109.7
Second stage, tons>	32.2
Fly-back propellant weight, tons	2.9
Launch site	Plesetsk

According to the most optimistic forecasts made by representatives of the Khrunichev Center in Le Bourget, the first Angara A1-V LV with the Baikal RB will be launched in 2-3 years. How­ever, the same implementation period was named two years ago at the previous air show in Le Bourget. Consequently, either the pace of work has not been high enough or the designers have come across serious technical and techno­logical difficulties. Khrunichev Center General Director Alexander Medvedev after the exhibi­tion gave a more realistic estimate of the first launch date for the Angara + Baikal combina­tion. “If everything succeeds from the financial point of view, I think 2006 is a fairly realistic date for its first launch with a light class launch vehicle,” Medvedev told the web publication Press Center.ru. “The development of Baikal is at its very early stage: we have carried out a number of projects and made four mock-ups for tunnel tests. We conducted a series of such tests at TsAGI at velocities of 0.5 to 10 speeds of sound. Molniya has done an invaluable job on the basis of the experience of Buran. We have already advanced to the publication of design plans and specifications. Three-four years after the first flight tests of Angara (its first launch is scheduled for 2003-2004 – ed.) we want to launch Baikal as well,” he said. Experts from the Khrunichev Center emphasize that Baikal is a multi-purpose booster that may be used with LV of varying classes, including U.S. space shuttles, the French Ariane LV and other carri­ers. Baikal will be the first stage of the Angara light LV. However, the market of light launch vehicles is not big enough to pay back the de­velopment of such an expensive reusable first stage. In the late 1980s – the first half of 1990s the world widely spoke of the brilliant pros­pects of light class launch vehicles because it was forecasted that the number of small space­craft operating in low orbits would radically in­crease and a whole series of low and medium orbit global satellite communication networks would be deployed. However, the number of properly funded small spacecraft projects at the stage of implementation has not grown that much in the past few years. Satellite communi­cation networks based on nonstationary groups of small spacecraft have not proved economi­cally effective yet; therefore they are not broadly used. Hence, the scores of light class LV launches predicted ten years ago have not taken place. In this connection the potential of 200 flights designed for Baikal in the light LV class may simply not be used up before the booster becomes obsolete and its systems and units reach the end of their service life. There­fore the development of the Baikal RB may pay back only if it is applied in LV of the medium and even more so heavy classes that are in greater demand on the market.

The all-azimuthal Angara-V LV of the medium and heavy classes can be produced if the mounted universal rocket modules (URM) are replaced by Baikal RB. Thus the medium An­gara-A3 LV is expected to be equipped with two Baikal boosters making it Angara A3-V. Simi­larly if four mounted URM on Angara-A5 are replaced by four RB, it will be the Angara A5-V. Experts are also considering the use of Bai­kal boosters on the heavy Angara-A4 LV with an oxygen-hydrogen second stage (Angara A4-V LV). However, the use of two to four reusable boosters on one LV may cause a number of problems. Thus in case of Angara A5-V and An­gara A4-V, the tailplanes of two out of four boosters have to be made folding. Besides, there may be serious difficulties when four RBs sepa­rating from the LV simultaneously return to the airdrome of the space center.

The Khrunichev Center and NPO Molniya are also studying the possibility of launching Angara LV family with Baikal RB from the An-124 Ruslan (Condor) aircraft – another option for a reus­able “atmospheric” stage.

Besides, in the framework of advanced research the Khrunichev Center is working on fully reus­able systems consisting of Baikal and a reusable second stage. However, their materialization is a matter of a more distant future and is not a pri­ority of the Center today.

Experts at Khrunichev Center believe that the consistent development of such reusable “atmospheric” stages should inevitably lead to the construction of hypersonic launch aircraft of space stages. To become single stage aerospace reusable vehicles they only have to be equipped with highly efficient combined rocket-air en­gines. However, the development of such en­gines evidently requires more advanced tech­nologies than the world today, not only the Khrunichev Center currently has at its disposal.

Parameters of Angara-V LV with Baikal RB

LV	Angara ?1-V	Angara ?3-V	Angara ?5-V	Angara ?4-V
Launch weight, tons	168.9	446	709	700
Number of RB at first stage	1	2	4	4
Propellants:
First stage	?2+kerosene	?2+kerosene	?2+kerosene	?2+kerosene
Second stage	Nitrogen tetroxide + UDMH	?2+kerosene	?2+kerosene	?2+H2
Payload launched from Plesetsk space center to:
LEO, tons	1.9	9.3	18.4	22.0
Geo-transfer orbit, tons	-	1.0	4.4	5.66
GSO, tons	-	-	2.5	3.2

Therefore, the road paved by the advanced re­search at the Khrunichev Center and NPO Molniya, as the engineers at both believe, will lead to the materialization of the old dream of aerospace equipment designers – the development of spacecraft capable of flying in space with the same effectiveness as aircraft does in current air traffic in the atmosphere of the Earth.

Sources: releases of the Khrunichev Center, NPO Molniya, reports of Interfax news agency, the Military News Agency and Press Center.ru.