STS-91

Key takeaways

STS-91 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect STS-91 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of STS-91 from memory before moving on to harder problems.

Reference excerpt

STS-91 was the 24th flight of Discovery, and the final Space Shuttle mission to the Mir space station. It was flown by Space Shuttle Discovery, and launched from Kennedy Space Center, Florida, on 2 June 1998.

Crew

Crew seat assignments

Mission highlights STS-91 marked the final Shuttle/Mir Docking Mission, as well as the only such docking for Discovery. This Phase 1 Program was a precursor to the International Space Station maintaining a continuous American presence in space and developing the procedures and hardware required for an international partnership in space. The mission was the first to use the super lightweight external tank (SLWT) which was the same size, at 154 feet (47 m) long and 27 feet (8.2 m) in diameter, as the external tank used on previous launches, but 7,500 pounds (3,400 kg) lighter. The tank was made of an aluminium lithium alloy and the tank's structural design had also been improved making it 30 percent stronger and 5 percent less dense. The walls of the redesigned hydrogen tank were machined in an orthogonal waffle-like pattern, providing more strength and stability than the previous design. These improvements would later provide additional payload capacity to the International Space Station. Docking of Discovery to Mir, the first for that orbiter, occurred at 16:01 UTC, 4 June 1998 at an altitude of 208 miles. Hatches opened at 2:34 pm the same day. At hatch opening, Andy Thomas officially became a member of Discovery's crew, completing 130 days of living and working on Mir. The transfer wrapped up a total of 907 days spent by seven U.S. astronauts aboard the Russian space station as long-duration crew members. During the next four days, the Mir 25 and STS-91 crews transferred more than 500 kilograms (1,100 lb) of water, and almost 2,130 kilograms (4,700 lb) of cargo experiments and supplies were exchanged between the two spacecraft. During this time, long-term U.S. experiments aboard the Mir were moved into Discovery's middeck locker area and the SPACEHAB single module in the orbiter's payload bay, including the Space Acceleration Measurement System (SAMS) and the tissue engineering co-culture (COCULT) investigations, as well as two crystal growth experiments. The crews also conducted Risk Mitigation Experiments (RMEs) and Human Life Sciences (HLS) investigations. When the hatches closed for undocking at 9:07 am, 8 June, and the spacecraft separated at 12:01 pm that day, the final Shuttle-Mir docking mission was concluded and Phase 1 of the International Space Station (ISS) program came to an end.

STS-91 also carried a prototype of the Alpha Magnetic Spectrometer (AMS) into space. The AMS, designed to look for dark and missing matter in the universe, was powered up on Flight Day 1. Data originally planned to be sent to ground stations through Discovery's Ku-band communications system was recorded on board because of a problem with the Ku-band system that prevented it from sending high-rate communications, including television signals, to the ground. The system was able to receive uplink transmissions. On 3 June 1998 the crew was able to set up a bypass system that allowed AMS data to be downlinked via S-band/FM communications when the orbiter came within range of a ground station. Data that could not be recorded by ground stations was recorded on board throughout the mission. The Ku-band system failure was determined to be located in a component that was not accessible to the crew. The failure prevented television transmission throughout the mission. Television broadcasts from Mir were prevented by a problem between a Russian ground station and the mission control center outside Moscow, limiting communications to audio only on NASA television. Other experiments conducted by the Shuttle crew during the mission included a checkout of the orbiter's robot arm to evaluate new electronics and software and the Orbiter Space Vision System for use during assembly missions for the ISS. Also on board in the payload bay were eight Get Away Special experiments, while combustion, crystal growth and radiation monitoring experiments were conducted in Discovery's mid-deck crew cabin area.

Illustrations

Worked examples

Example 1 — a first encounter with STS-91

Start with the simplest possible case. Write down what STS-91 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 STS-91 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 STS-91 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 STS-91

In research: STS-91 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 STS-91 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: STS-91 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Human spaceflights to Mir, Space Shuttle missions, Spacecraft launched in 1998, so understanding it makes those chapters shorter.
In everyday life: Look for STS-91 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.

How to study STS-91 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what STS-91 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 STS-91 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is STS-91 in simple terms?

STS-91 was the 24th flight of Discovery, and the final Space Shuttle mission to the Mir space station. It was flown by Space Shuttle Discovery, and launched from Kennedy Space Center, Florida, on 2 June 1998.

Why does STS-91 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 STS-91?

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 STS-91.