MiG-105 and the Spiral Program: The Soviet Vision for an Orbital Spaceplane
In the mid-1960s, Soviet engineers began conceptualizing a revolutionary approach to spaceflight: the Spiral program. Known formally as the Experimental Passenger Orbital Aircraft (EPOS), this ambitious project aimed to develop an orbital spaceplane capable of returning to Earth with precision. While the full-scale spaceplane was never realized, the development of the MiG-105 test vehicle provides a fascinating window into the Soviet Union's competitive response to the U.S. Space Shuttle Program.
The MiG-105, nicknamed "Lapot" (meaning "bast shoe" in Russian) due to the distinctive shape of its nose, served as a crucial crewed test vehicle. Its primary mission was to explore the complexities of low-speed handling and landing characteristics essential for a reusable spacecraft.
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Key Facts
- Project Name: Spiral (also known as EPOS)
- Test Vehicle: MiG-105-11
- Manufacturer: Mikoyan
- Primary Goal: To develop a crewed orbital spaceplane
- Launch Concept: "50/50" midair launch from a hypersonic mothership
- Status: Cancelled in favor of the Buran project
The Evolution of the Spiral Concept
The development of the Spiral program was non-linear. Work initially began in 1965 but was halted in 1969. However, the project was revived in 1974 as the Soviet Union sought to match American advancements in reusable spacecraft technology. The MiG-105 made its first subsonic free-flight test in 1976, taking off from an airstrip near Moscow. A total of eight flight tests were conducted sporadically between 1976 and 1978.
The "50/50" Launch Scheme
Unlike the vertical rocket launches common in spaceflight, the Spiral concept utilized a unique midair launch scheme. This method, dubbed "50/50," involved a custom-built hypersonic mothership—to be designed by the Tupolev Design Bureau—carrying the spaceplane and a liquid fuel booster stage to high altitudes before release. This mothership was intended to leverage technologies from the Tu-144 supersonic transport and the Sukhoi T-4 bomber.
Innovative Design and Thermal Protection
The Spiral was designed as a conventional delta wing aircraft featuring variable-dihedral wings. To optimize performance, these wings would fold upward at a 60-degree angle during launch and reentry. Once the vehicle reached subsonic speeds after reentry, the pilot could lower the wings to a horizontal position to improve flight characteristics for landing.
To survive the intense heat of reentry, engineers developed scale-plate armour. This system utilized niobium alloy (VN5AP) and molybdenum disilicide plated steel plates. These plates were mounted on articulated ceramic bearings, a design choice that allowed for thermal expansion during the extreme temperature shifts of atmospheric reentry.
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Safety and Landing Mechanisms
Safety was a paramount concern in the Spiral design. In the event of an in-flight emergency or a booster explosion, the crew compartment was engineered to separate from the main vehicle and descend via parachute, functioning much like a traditional ballistic capsule. For landing, the spaceplane was designed to use skids that deployed from doors located on the sides of the fuselage, just above and ahead of the wings. Additionally, a single Kolesov turbojet engine, protected by a clamshell door, allowed for powered landings and go-around maneuvers.
The BOR Reentry Test Vehicles
To test the Spiral's reentry capabilities, the Soviet Union utilized a series of uncrewed, sub-scale reentry test vehicles known as BOR (Bespilotnyi Orbital'nyi Raketoplan, or Unpiloted Orbital Rocketplane). These vehicles served as functional analogs to the American X-23 PRIME and ASSET programs.
| Type | Launch Date | Usage | Current Status |
|---|---|---|---|
| BOR-1 | 15.07.1969 | 1:3 scale experimental model | Burned during test |
| BOR-2 | 1969–1972 | Sub-scale Spiral model (4 launches) | NPO Molniya, Moscow |
| BOR-3 | 1973–1974 | Sub-scale Spiral model (2 launches) | Crashed on landing |
| BOR-4 | 1980–1984 | Sub-scale Spiral model (4+ launches) | NPO Molniya, Moscow |
| BOR-5 | 1984–1988 | Sub-scale base model (5 launches) | Museums in Germany and Russia |
| BOR-6 | N/A | Sub-scale Spiral model | NPO Molniya, Moscow |
Technical Specifications: MiG-105-11
The following data represents the specifications for the MiG-105-11 test vehicle used during the flight test program:
General Characteristics
- Crew: 1
- Length: 10.6 m (34 ft 9 in)
- Wingspan: 6.7 m (22 ft 0 in)
- Empty Weight: 3,500 kg (7,716 lb)
- Gross Weight: 4,220 kg (9,304 lb)
- Powerplant: 1 × RD-36-35K turbojet (19.61 kN thrust)
Performance
- Maximum Speed: 800 km/h (Mach 0.65)
- Landing Speed: 250–270 km/h
- Wing Loading: 175 kg/m²
Frequently Asked Questions
Why was the Spiral program cancelled?
The Spiral project was ultimately cancelled when the Soviet Union decided to prioritize the development of the Buran project instead.
What does the nickname "Lapot" mean?
"Lapot" is Russian for "bast shoe," a nickname given to the MiG-105 because of the specific shape of its nose.
Where can I see the MiG-105 today?
The MiG-105 test vehicle is currently preserved and on display at the Monino Air Force Museum in Russia.
How did the Spiral plan to protect the pilot during reentry?
The design included a crew compartment that could separate from the vehicle and descend via parachute in the event of an emergency.
What was the purpose of the BOR vehicles?
The BOR series were uncrewed, sub-scale rocketplanes used to test the reentry and aerodynamic concepts intended for the full-scale Spiral spaceplane.