SL-4 R/B (21561)

COSPAR: 1991-049B | Alt Name: Soyuz-U 59-726 Blok-I
DECAYED

Image
SL-4 R/B Satellite Image
Additional Sources
Launch Details

Launch Date

July 10, 1991

Launch Pad

LC31

Launch Vehicle

Soyuz-U

Orbital Elements

NORAD ID

21561

International Designator

1991-049B

Decay Date

7/13/1991

Basic Satellite Info

Name

SL-4 R/B

Alternative Name

Soyuz-U 59-726 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

Unknown

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.

Iran Struck U.S. Aircraft Despite 'Maxed Out' Defense | KeepTrack Space Brief

Iran Struck U.S. Aircraft Despite 'Maxed Out' Defense | KeepTrack Space Brief

Iran successfully struck U.S. aircraft in Saudi Arabia despite maxed-out defensive posture. Space Force ISR and missile warning gaps exposed. Tracking impacts.

Space Brief 9 Sep 2024

Space Brief 9 Sep 2024

Today's Space Brief explores new satellite launches, significant reentries, funding milestones, and critical policy updates.

Space Brief 1 Jun 2025

Space Brief 1 Jun 2025

Today's highlights cover critical satellite launches including SpaceX's GPS III mission, advancements in SATCOM technology, and changes in NASA leadership.

Space Brief 10 Feb 2025

Space Brief 10 Feb 2025

Discover today's key space events: SpaceX's Starlink launch, rocket debris risks, and advancements in nuclear rocket technology.

The Day America's Revolutionary Rocket Design Made Its Final Flight

The Day America's Revolutionary Rocket Design Made Its Final Flight

Twenty years ago, an Atlas rocket carrying a classified payload lifted off from Cape Canaveral, marking the end of a revolutionary spacecraft design that helped launch America into the Space Age

X Report 7 Dec 2024

X Report 7 Dec 2024

SpaceX celebrates 300 successful booster landings, further solidifying its dominance in reusable rocket technology.

Space Brief 6 Dec 2024

Space Brief 6 Dec 2024

Today's brief covers various military applications of climate-monitoring satellites, new defense strategies against unmanned threats, and the potential impacts of geopolitical tensions on orbit.

X Report 30 Oct 2025

X Report 30 Oct 2025

SpaceX continues to ramp up its operations with the launch of 29 more Starlink satellites, while significant upgrades at its Starbase facility signify ambitious future plans.