Space Brief 2 Apr 2025
DARPA's accidental SpaceX detection highlights Earth as a natural sensor, while SpaceX's Fram2 launches into a polar orbit. Helsinki's defense budget rise hints at increased military satellite activity.
SL-4 R/B (21736)
COSPAR: 1991-069B | Alt Name: Soyuz-U2 No. 054 Blok-I
DECAYED
Image
Additional Sources
Launch Details
Launch Date
October 2, 1991
Launch Site
Launch Pad
LC1
Launch Vehicle
Soyuz-U2
Orbital Elements
NORAD ID
21736
International Designator
1991-069B
Decay Date
10/3/1991
Basic Satellite Info
Name
SL-4 R/B
Alternative Name
Soyuz-U2 No. 054 Blok-I
Type
Rocket Body
Status
Space Junk
Owner
RVSN
Country
USSR
Constellation
N/A
Related Satellites
Major Events
N/A
Summary
A rocket body, also commonly referred to as an upper stage or spent rocket stage, is the structural shell left behind after a rocket has delivered its payload to orbit. These large and often heavy pieces of space hardware can remain in orbit for years, posing significant collision hazards as part of the growing space debris problem. If left uncontrolled, rocket bodies have the potential to reenter Earth's atmosphere unpredictably, which can lead to falling debris in populated areas. Additionally, they risk colliding with operational satellites or the International Space Station, creating more debris and putting human life at risk.
Physical Characteristics
Length
6.7
Diameter
2.7
Span
6.7
Dry Mass
2350
Launch Mass
2350
Shape
Cyl
Radar Cross Section
14.31
Visual Magnitude
Unknown
Color
Unknown
Material Composition
Unknown
Technical Details
Payload
11S510
Purpose
Unknown
Mission
Unknown
Manufacturer
PROG
Life Expectancy
Unknown
Bus
Blok-I
Configuration
Unknown
Motor
Unknown
Equipment
Unknown
Power System
Unknown
ADCS
Unknown
Transmitter Frequency
Unknown
Satellite Articles
View All Posts »Learn more about satellites and other related topics.
GAO Warns Space Force Satellite Costs Rising, Workforce Cuts Add Risk | KeepTrack Space Brief
GAO flags growing cost problems across Space Force satellite portfolio with workforce reductions compounding risks to missile-warning constellations like NGG and SWAT.
X Report 25 Oct 2025
SpaceX prepares for a record-setting launch of Starlink satellites, while Iridium faces challenges against SpaceX's expanding services.
Space Brief 10 Dec 2025
Today's brief covers China's intense launch schedule, a new Arctic military constellation, Muon Space's defense innovations, and SpaceX's classified NROL-77 mission.
Space Brief 5 Dec 2025
Focusing on military satellite initiatives, defense strategies, and advancements in air and cyber capabilities
X Report 6 Aug 2025
SpaceX has adapted Pad 1 for Ship Static Fire tests while addressing the recent downtime at Massey’s, showcasing its commitment to maintaining launch schedules despite setbacks.
Space Brief 21 Nov 2025
Today's brief covers the Space Force's strategic roadmap, a groundbreaking DARPA mission in Very Low Earth Orbit, and enhanced cyber defenses due to AI-driven threats.
Space Brief 21 May 2025
Today's Space Brief covers significant events including a high-stakes missile defense program, recent Chinese satellite launches, military defense initiatives, and key profiles in defense leadership.