science

Return of Apollo 15 to Earth

Return of Apollo 15 to Earth 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 Return of Apollo 15 to Earth rather than just read about it. In short: After the Apollo 15 LM Falcon lifted from the lunar surface on August 2, 1971, it rendezvoused and docked with the CSM Endeavour. After transferring across the lunar samples and other equipment, Falcon was jettisoned.

Key takeaways

Return of Apollo 15 to Earth belongs to science; place it in that map before memorising details.
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Connect Return of Apollo 15 to Earth to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Return of Apollo 15 to Earth from memory before moving on to harder problems.

Reference excerpt

After the Apollo 15 LM Falcon lifted from the lunar surface on August 2, 1971, it rendezvoused and docked with the CSM Endeavour. After transferring across the lunar samples and other equipment, Falcon was jettisoned. It would fire its rocket engine to cause it to impact the lunar surface. Apollo 15 spent one more day in lunar orbit, continuing Worden's observations. After releasing a subsatellite, they ignited their service propulsion system to put them on a trajectory back to Earth. The next day, Worden performed an EVA to retrieve the film cassettes from the scientific instrument module (SIM) bay cameras. The twelfth day in space was uneventful, with Mission Control holding a press conference where the astronauts were asked questions submitted by the news media. On their 13th and final day they prepared for reentry. During descent one of their three parachutes failed, and they splashed down successfully with only two.

Rendezvous and docking Falcon lifted off from the lunar surface after 171 hours, 37 minutes and 16 seconds GET. ("Ground Elapsed Time" from the time of liftoff from Earth) During ascent from the Moon, Worden played "The Air Force Song". Although he thought it was only being played for Houston, unbeknownst to him, a switch had been flicked in Mission Control that relayed his voice transmissions to the LM. It is understood that Scott was not very happy with this, as it was impossible to make out any communications from Mission Control while the song played.

The LM was placed into a 42 by 9 nm (77.8 by 16.7 km) orbit. Apollo 15 would be the first direct rendezvous, where the two craft would rendezvous within one orbit. The LM orbit was not perfectly in the same plane as the CSM's, so another burn of the LM's ascent engine was required. During the following near side pass, the spacecraft continued to close, with Falcon, in its lower orbit, catching Endeavour. Once about 120 feet (40 m) apart the spacecraft started to station-keep — keeping the distance between them constant. As on all Apollo flights, the crew extensively photographed and filmed this process. Endeavour closed in to hard dock and the mission of Falcon had come to an end.

After opening the hatches, the crew began the task of transferring the rock samples that had been collected on the surface. Scott and Irwin also vacuumed their spacesuits to try to rid them of as much dust as possible. Also transferred were film magazines, food, used urine and fecal bags (they were included for medical investigators). One Oxygen Purge System (OPS) was also transferred. On the lunar surface the OPS would be used as an emergency oxygen supply, or by the crew of the LM in the event that they were unable to achieve hard docking with the CSM and had to undertake an EVA to transfer across from the LM. Worden would use it during his EVA later in the mission. Following the completion of the transfer, the crew resealed the hatches between the two craft and prepared to jettison the LM. This was different from the undocking that took place before landing. In this case it would be an explosive jettison as much of the docking probe structure was now unneeded and would stay in the LM. There was some difficulty in getting the tunnel between the craft to depressurize. This suggested that there was an improperly sealed hatch, delaying the separation by one orbit. After checking the hatches the crew could not find a cause for the improper seal, but the tunnel now vented successfully. In his 2001 memoir, Flight Director Christopher Kraft wrote that some of these difficulties may have been the result of crew fatigue. Because of the longer lunar stay time, by this point Scott and Irwin had gone an arduous 22 hours without sleep, and both men had experienced some heart irregularities on the lunar surface after their EVAs. Kraft wrote that coordination between ground controllers and the crew broke down several times at this point in the mission, and he recalled this as one of the most stressful experiences during his career in mission control. A change in crew procedure had come after the deaths of three crewmembers of Soyuz 11 less than a month before the launch of Apollo 15. On Soyuz 11 the crew had been killed after a repressurization valve opened during the separation of the orbital and service modules from the reentry module of the Soyuz spacecraft. Mission planners for Apollo 15 decided that the crew should now wear their pressure suits during the separation of the LM from the CSM, something that had not previously occurred. The suits caused some problems for 15 as during an integrity test before the tunnel venting they were unable to achieve suit integrity in Scott's suit. After finally jettisoning the LM, the CSM performed a small RCS (reaction control system) burn to further separate from the LM. Falcon was directed to burn its ascent stage engine, so that it would impact the lunar surface. The delay has meant it would not impact in the planned site, instead impacting at 26°12' N, 0°6' E, about 56 miles (90 km) from the landing site. The crew should have started their sleep period, but due to the delays now had to finish housekeeping chores. Mainly these centered around turning back on the SIM instruments which had been turned off during the rendezvous and docking and orientating the spacecraft for their proper use. Just before the sleep period, Deke Slayton, who was effectively the astronauts' boss, radioed the crew and told them to take a Seconal sedative. The crew decided against this. Doctors on the ground had become worried when they saw that Scott's and Irwin's EKG had developed a bigeminy rhythm. Caused by a lack of potassium, the ventricles beat in couplets, instead of a single constant beat. The potassium deficiency is thought to have been caused by the training schedule and stress of the flight. Irwin would later die in 1991 of a heart attack. Finally 3½ hours after they were meant to go to sleep and 2 hours after Mission Control first said good night to the crew, they started their sleep period on the 54th orbit of the Moon. Scott and Irwin had been awake over 23 hours and Worden 21 hours.

Last day in lunar orbit and TEI

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Return of Apollo 15 to Earth

Start with the simplest possible case. Write down what Return of Apollo 15 to Earth 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 Return of Apollo 15 to Earth 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 Return of Apollo 15 to Earth 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 Return of Apollo 15 to Earth

In research: Return of Apollo 15 to Earth 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 Return of Apollo 15 to Earth 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: Return of Apollo 15 to Earth is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alfred Worden, Apollo 15, David Scott, so understanding it makes those chapters shorter.
In everyday life: Look for Return of Apollo 15 to Earth 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 Return of Apollo 15 to Earth in 20 minutes

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Frequently asked questions

What is Return of Apollo 15 to Earth in simple terms?

Why does Return of Apollo 15 to Earth 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 Return of Apollo 15 to Earth?

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 Return of Apollo 15 to Earth.