science

Soyuz 21

Soyuz 21 is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Soyuz 21 rather than just read about it. In short: Soyuz 21 (Russian: Союз 21, Union 21) was a 1976 Soviet crewed mission to the Salyut 5 space station, the first of three flights to the station. The mission's objectives were mainly military in scope, but included other scientific work.

Key takeaways

Soyuz 21 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Soyuz 21 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Soyuz 21 from memory before moving on to harder problems.

Reference excerpt

Soyuz 21 (Russian: Союз 21, Union 21) was a 1976 Soviet crewed mission to the Salyut 5 space station, the first of three flights to the station. The mission's objectives were mainly military in scope, but included other scientific work. The mission ended abruptly with cosmonauts Boris Volynov and Vitaly Zholobov returning to Earth after 49 days in orbit. The precise reason for the early end of the mission was the subject of much speculation, but was reported to be an emergency evacuation after the Salyut atmosphere developed an acrid odor, possibly from "the station's atmosphere becoming toxic as a result of the chemicals being used to expose surveillance photographs. By some accounts, Zholobov, in particular, fell ill."

Crew

Backup crew

Reserve crew

Mission parameters Mass: 6,750 kg (14,880 lb) Perigee: 193.0 km (119.9 mi) Apogee: 253.0 km (157.2 mi) Inclination: 51.6° Period: 88.7 minutes

Mission highlights Salyut 5, the last dedicated military space station in the Soviet space program, was launched 22 June 1976. Its first crew was launched 14 days later on 6 July 1976, with Commander Volynov and Flight engineer Zholobov aboard Soyuz 21. Based on landing opportunities, observers estimated the mission was intended to last 54 to 66 days. They docked with the station the next day, and gave a televised tour 8 July 1976. Their stay coincided with the start of the Siber military exercise in Siberia, which they observed as part of an assessment of the station's military surveillance capabilities. They conducted only a few scientific experiments, including the first use of the Kristall furnace for crystal growth. Engineering experiments included propellant transfer system tests with implications for future operation of the freight-carrying Progress spacecraft. Experiments conducted during the mission were mainly of a military nature as part of the Almaz program. Various purely scientific tasks were also carried out, including solar observations and biological observations of an aquarium of fish carried into orbit. A television link-up with school children on 17 August 1976 was also undertaken. On 24 August 1976, it was announced the mission was to end in only 10 hours, a development which caught even the reporters of Radio Moscow by surprise. The reason for the sudden termination of the mission was reported at the time to have been an acrid odor that developed in the environmental control system. The problem was said to have begun as early as 17 August 1976. The Soviets made no comments at the time, but the next crew to board the station wore breathing masks. Later reports indicate that the mission may have ended owing to a deterioration in the health of Zholobov. The mission was to last two months but was cut short by a gradually worsening illness of Zholobov. The cosmonauts boarded Soyuz 21 but as Volynov tried to undock from the station, the docking latches failed to release properly. As he fired the jets to move the spacecraft away, the docking mechanism jammed, resulting in the Soyuz being undocked but still linked to Salyut. As the two spacecraft moved out of range of ground communications, the cosmonauts received only the first set of emergency procedures. Volynov tried a second time to undock but only managed slightly to loosen the latches. The situation persisted for an entire orbit, 90 minutes, when the final set of emergency procedures were received and the crew finally disengaged the latches. Because Soyuz 21 was returning early, it was outside the normal recovery window. It then encountered strong winds as it descended, which caused uneven firing of the retrorockets. It made a hard landing around midnight 200 km (120 mi) at the southwest of Kokchetav, Kazakhstan. Zholobov's illness was apparently caused by nitric acid fumes leaking from the Salyut's propellant tanks; other reports, however, indicate that the crew failed to follow their physical exercise program and suffered from lack of sleep. Sources at NASA have reported that psychologists with the Russian Aviation and Space Agency cited Soyuz 21 as ending prematurely due to unspecified "interpersonal issues" with the crew. The next mission to successfully dock with the station, Soyuz 24, would vent Salyut 5's air to space and replace it due to concerns the air had become toxic.

References

Illustrations

Worked examples

Example 1 — a first encounter with Soyuz 21

Start with the simplest possible case. Write down what Soyuz 21 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Soyuz 21 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Soyuz 21 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Soyuz 21

In research: Soyuz 21 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Soyuz 21 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Soyuz 21 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1976 in the Soviet Union, Crewed Soyuz missions, Human spaceflights to Salyut space stations, so understanding it makes those chapters shorter.
In everyday life: Look for Soyuz 21 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Soyuz 21 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Soyuz 21 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Soyuz 21 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Soyuz 21 in simple terms?

Why does Soyuz 21 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Soyuz 21?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Soyuz 21.