science

Kosmos 391

Kosmos 391 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 Kosmos 391 rather than just read about it. In short: Kosmos 391 (Russian: Космос 391 meaning Cosmos 391), also known as DS-P1-I No.11 was a satellite which was used as a radar target for anti-ballistic missile tests. It was launched by the Soviet Union in 1971 as part of the Dnepropetrovsk Sputnik programme.

Key takeaways

Kosmos 391 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Kosmos 391 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kosmos 391 from memory before moving on to harder problems.

Reference excerpt

Kosmos 391 (Russian: Космос 391 meaning Cosmos 391), also known as DS-P1-I No.11 was a satellite which was used as a radar target for anti-ballistic missile tests. It was launched by the Soviet Union in 1971 as part of the Dnepropetrovsk Sputnik programme.

Launch It was launched aboard a Kosmos-2I 63SM rocket, from Site 133/1 at Plesetsk. The launch occurred at 12:00:00 UTC on 14 January 1971.

Orbit Kosmos 391 was placed into a low Earth orbit with a perigee of 267 kilometres (166 mi), an apogee of 803 kilometres (499 mi), 70.9 degrees of inclination, and an orbital period of 95.3 minutes. It decayed from orbit on 21 February 1971. Kosmos 391 was the tenth of nineteen DS-P1-I satellites to be launched. Of these, all reached orbit successfully except the seventh.

Worked examples

Example 1 — a first encounter with Kosmos 391

Start with the simplest possible case. Write down what Kosmos 391 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 Kosmos 391 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 Kosmos 391 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 Kosmos 391

In research: Kosmos 391 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 Kosmos 391 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: Kosmos 391 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1971 in spaceflight, 1971 in the Soviet Union, Dnepropetrovsk Sputnik program, so understanding it makes those chapters shorter.
In everyday life: Look for Kosmos 391 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 Kosmos 391 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kosmos 391 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 Kosmos 391 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kosmos 391 in simple terms?

Why does Kosmos 391 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 Kosmos 391?

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 Kosmos 391.