Проверить пропуск в зону ато по фамилии: РЕЄСТР ДОЗВОЛІВ ДЛЯ ПЕРЕМІЩЕННЯ ОСІБ ЧЕРЕЗ ЛІНІЮ ЗІТКНЕННЯ У МЕЖАХ ДОНЕЦЬКОЇ ТА ЛУГАНСЬКОЇ ОБЛАСТЕЙ

Как проверить, не аннулирован ли цифровой пропуск в Москве в период самоизоляции

Москва перешла на систему пропусков из-за сложной эпидемиологической ситуации. Для передвижения по городу необходимо получить электронный пропуск. Предъявить его нужно, если остановил сотрудник ГИБДД, а также при посадке в такси, при использовании метро.

Всего за сутки в столице уже оформили 3,2 млн цифровых пропусков для передвижения по городу на личном или общественном транспорте. Из них 900 тысяч пропусков будут аннулированы, так как были предоставлены некорректные или недостоверные данные. В Департаменте информационных технологий объяснили, что люди вводили фамилии с цифрами, нулевые и некорректные номера паспортов, неточно заполняли поля ИНН.

— Мы убедительно просим горожан не оформлять пропуска «просто так», для галочки или «на всякий случай», — сказал руководитель Департамента информационных технологий Эдуард Лысенко.

Поделиться видео </>

Жители Москвы накануне введения пропускного режима.

Если человеку не нужно на работу, то лучше просто оставаться дома, соблюдая правила самоизоляции. А пропуска нужны тем, кто вынужден покинуть квартиру.

— Пропуска выдаются по заявительному принципу, однако все сведения в дальнейшем проверяются, особенно данные о работодателях. В случае если какие-либо данные будут введены некорректно или окажутся недостоверными, пропуск будет аннулирован, а граждане, указавшие недостоверную информацию, будут привлечены к административной ответственности, — объяснил Эдуард Лысенко.

Проверять пропуска будут с 15 апреля. И вот здесь возникает вопрос: как проверить не аннулирован ли пропуск для поездок по Москве? Ведь кто-то может и балуется, оформляя пропуска, а кто-то случайно допустил ошибку при оформлении. Как быть? Рассказываем.

Как проверить, работает ли мой цифровой пропуск?

1. «Если ваш пропуск будет аннулирован, вы получите сообщение об этом на электронную почту или номер телефона, указанные при подаче заявки», — объясняют на портале мэра mos.ru.

2. Впрочем, проверить, активен ли ваш пропуск, можно и самостоятельно. Для этого нужно зайти на все тот же сайт nedoma.mos.ru и кликнуть на кнопку «Проверить цифровой пропуск».

Для передвижения по городу необходимо получить электронный пропуск.Фото: Иван МАКЕЕВ

Напомним, что пропуска нужно оформить тем, кто использует для передвижения по Москве транспорт (личный или общественный).

Выйти в магазин за хлебом, в аптеку за лекарствами или выгулять собаку по-прежнему можно без пропуска. При этом важно соблюдать правила и ограничения, установленные указом Мэра Москвы.

Как оформить цифровой пропуск?

— онлайн на портале mos.ru (nedoma.mos.ru),

— по телефону +7 (495) 777-77-77,

— с помощью смс на номер 7377, нужно указать цифру: 1 — для работающих, 2 – разовая поездка в больницу, 3 – разовая поездка в иных целях.

Поделиться видео </>

Как оформить пропуск передвижения по Москве.С 13 апреля для поездок на личном и общественном транспорте по Москве потребуется цифровой пропуск. Оформить его можно несколькими способами

ТЕМ ВРЕМЕНЕМ

Спецпропуска в Москве: самое главное, что вам нужно о них знать

Пешеходам спецпропуска оформлять пока не нужно, но это не означает, что режим самоизоляции в Москве сняли (подробности)

Штрафы за нарушения с цифровыми пропусками в Москве: сколько составят и какие предусмотрены

С 15 апреля по Москве и Московской области разрешат ездить на личном и общественном транспорте только с цифровым пропуском. Их уже начали оформлять сегодня, 13 апреля, на портале мэра mos.ru. Напомним, такой указ подписал мэр Москвы Сергей Собянин из-за ухудшения ситуации с коронавирусом (подробности)

Почему могут аннулировать цифровой пропуск в Москве и как проверить, работает ли он

Некоторые москвичи жалуются, что через какое-то время после оформления их пропуск оказывается аннулирован. Итак, давайте разберемся, почему это может происходить (подробности)

90000 Were there alternatives to the atomic bombings? 90001 90002 As we rapidly approach the 70th anniversary of the bombings of Hiroshima and Nagasaki, there have been all sorts of articles, tributes, memorials, and so forth expressed both in print and online. I’ve been busy myself with some of this sort of thing. I was asked if I would write up a short piece for Aeon Ideas about whether there were any alternatives to these bombings, and I figure it will not hurt to cross-post it here as well.90003 90002 An unusual photograph of the late clouds of Hiroshima, as seen from the air. This was probably taken by aircraft that arrived several hours after the bombing to do damage reconnaissance; they reported the target was obscured by huge amounts of smoke. Source: National Archives and Records Administration, via Fold3.com. 90003 90002 The point of the piece, I would like to emphasize, is not necessarily to «second guess» what was done in 1945. It is, rather, to point out that we tend to constrain our view of the possibilities generally to one of two unpleasant options.Many of those who defend the bombings seem to end up in a position of believing that 1. there were no other options on the table at the time except for 90007 exactly 90008 what did occur, and 2. that questioning whether there were other options does historical damage. As a historian, I find both of these positions absurd. First, history is full of contingency, and there were several explicit options (and a few implicit ones) on the table in 1945 — more than just «bomb» versus «invade.» These other options did not carry the day does not mean they should be ignored.Second, I think that pointing out these options helps shape our understanding of the choices that 90007 were 90008 made, because they make history seem less like a fatalistic march of events. The idea that things were «fated» to happen the way they do does much more damage to the understanding of history, because it denies human influence and it denies choices were made. 90003 90002 Separately, there is a question of whether we ought to «judge» the past by standards of the present. In some cases this leads to statements that are simply non-sequiturs — I think Genghis Khan’s methods were inhumane, but who cares that I think that? But World War II was not so long ago that its participants are of another culture entirely, and those who say we should not judge the atomic bombings by the morality of the present neglect the range of moral codes that were available at the time.The idea that burning civilians alive created a moral hazard was hardly unfamiliar to people in 1945 року, even if they did it anyway. Similarly, I will note that the people who adopt such a position of historical moral relativism never seem to apply it to nations that fought against their countries in war. 90003 90002 Anyway, all of the above is meant as a disclaimer, in case anyone wonders what my intent is here. It is not to argue that the leaders of 1945 necessarily ought to have done anything different than they did.It is merely to try and paint a picture of what sorts of possibilities were on the table, but were not pursued, and to try and hack away a little bit at the false dichotomy that so often characterizes this discussion — a dichotomy, I might note , that was started explicitly as a propaganda effort by the people who made the bomb and wanted to justify it against mounting criticism in the postwar. I believe that rational people can disagree on the bombings of Hiroshima and Nagasaki. 90003 90016 90002 90007 90019 What options were there for the United States regarding the atomic bomb in 1945? 90020 90008 90003 90002 Few historical events have been simultaneously second-guessed and vigorously defended as the atomic bombings of Hiroshima and Nagasaki, which occurred seventy years ago this August.To question the bombings, one must assume an implicit alternative history is possible. Those who defend the bombings always invoke the alternative of a full-scale invasion of the Japanese homeland, Operation Downfall, which would have undoubtedly caused many American and Japanese casualties. The numbers are debatable, but estimates range from the hundreds of thousands to the millions — an unpalatable option, to be sure. 90003 90002 These unusual before-and-after images come from the Report of the Joint Commission for the Investigation of the Effects of the Atomic Bomb on Japan, Volume I, «Medical Effects of Atomic Bombs,» NP-3036 (April 1951).I apologize for the poor image quality. I thought that even so they provide striking contrasts, and are much more easy to grasp that the familiar «view from above» photographs. This one is of the Hiroshima Commercial Museum, only 300 meters from Ground Zero, and now known as the famous «Genbaku dome.» The photographs are not labeled with when they were taken; the «before» photos seem like they are from the late 1930s, the «after» photos are likely no earlier than September 1945 року, and may be from 1946.90003 90002 But is this stark alternative the only one? That is, are the only two possible historical options available a bloody invasion of the Japanese home islands, or the dropping of two nuclear weapons on mostly-civilian cities within three days of one another, on the specific days that they were dropped? Well, not exactly. We can not replay the past as if it were a computer simulation, and to impose present-day visions of alternatives on the past does little good. But part of the job of being a historian is to understand the variables that were in the air at the time — the choices, decisions, and serendipity that add up to what we call «historical contingency,» the places where history could have gone a different direction.To contemplate contingency is not necessarily to criticize the past, but it does seek to remove some of the «set in stone» quality of the stories we often tell about the bomb. 90003 90002 90019 Varying the schedule. 90020 The military order that authorized the atomic bombings, sent out on July 25, 1945, was not specific as to the timing, other than saying that the «first special bomb» could be dropped «as soon as weather will permit visual bombing after about 3 August 1945. » Any other available bombs could be used «as soon as made ready by the project staff.»The Hiroshima mission was delayed until August 6th because of weather conditions in Japan. The Kokura mission (which became the Nagasaki mission) was originally scheduled for August 11th, but got pushed up to August 9th because it was feared that further bad weather was coming. At the very least, waiting more than three days after Hiroshima might have been humane. Three days was barely enough time for the Japanese high command to verify that the weapon used was a nuclear bomb, much less assess its impact and make strategic sense of it.Doing so may have avoided the need for the second bombing run altogether. Even if the Japanese had not surrendered, the option for using further bombs would not have gone away. President Truman himself seems to have been surprised by the rapidity with which the second bomb was dropped, issuing an order to halt further atomic bombing without his express permission. 90003 90002 «Komiya street (750 meters [from Ground Zero] before and after bombing. The archlike heavy lamp posts have fallen. One lies at the left of the lower photograph.»90003 90019 Demonstration. 90020 Two months before Hiroshima, scientists at the University of Chicago Metallurgical Laboratory, one of the key Manhattan Project facilities, authored a report arguing that the first use of an atomic bomb should not be on an inhabited city. The committee, chaired by Nobel laureate and German exile James Franck, argued that a warning, or demonstration, of the bomb on, say, a barren island, would be a worthwhile endeavor. If the Japanese still refused to surrender, then the further use of the weapon, and its further responsibility, could be considered by an informed world community.Another attractive possibility for a demonstration could be the center of Tokyo Bay, which would be visible from the Imperial Palace but have a minimum of casualties if made to detonate high in the air. Leo Szilard, a scientist who had helped launch the bomb effort, circulated a petition signed by dozens of Manhattan Project scientists arguing for such an approach. It was considered as high as the Secretary of War, but never passed on to President Truman. J. Robert Oppenheimer, joined by three Nobel laureates who worked on the bomb, issued a report, concluding that «we can propose no technical demonstration likely to bring an end to the war; we see no acceptable alternative to direct military use.»But was it feasible? More so than most people realize. Though the US only had two atomic bombs in early August 1945 року, they had set up a pipeline to produce many more, and by the end of the month would have at least one more bomb ready to use, and three or four more in September. The invasion of the Japanese mainland was not scheduled until November. So by pushing back the time schedule, the US could have still had at least as many nuclear weapons to use against military targets should the demonstration had failed.The strategy of the bomb would have changed — it would have lost some of its element of «surprise» — but, at least for the Franck Report authors, that would be entirely the point. 90002 90019 Changing the targets. 90020 The city of Hiroshima was chosen as a first target for the atomic bomb because it had not yet been bombed during the war (and in fact had been «preserved» from conventional bombing so that it could be atomic bombed), because the scientific and military advisors wanted to emphasize the power of the bomb.By using it on an ostensibly «military» target (they used scare quotes themselves!), «Located in a much larger area subject to blast damage,» they hoped both to avoid looking bad if the bombing was somewhat off-target (as the Nagasaki bombing was), and so that the debut of the atomic bomb was «sufficiently spectacular» that its importance would be recognized not only by the Japanese, but the world at large. But the initial target for the bomb, discussed in тисяча дев’ятсот сорок три (long before it was ready) was the island of Truk (now called Chuuk), an ostensibly purely military target, the Japanese equivalent of Pearl Harbor.By 1945 року, Chuuk had been made irrelevant, and much of Japan had already been destroyed by conventional bombing, but there were other targets that would not have been so deliberately destructive of civilian lives. As with the «demonstration,» option had the effect not been as desired, escalation was always available as a future option, rather than as the first step. 90003 90002 «Prefectural Office (900 meters [from Ground Zero]) before and after the bombing. The wooden structure has collapsed and burned.Note displacement of the heavy granite blocks of the wall. » 90003 90019 Clarifying the Potsdam Declaration. 90020 By the summer of 1945 року, a substantial number of the Japanese high command, including the Emperor, were looking for a diplomatic way out of the war. Their problem was that the Allies had, with the Potsdam Declaration, continued to demand «unconditional surrender,» and emphasized the need to remove «obstacles» preventing the «democratic tendencies» of the Japanese people. What did this mean, for the postwar Japanese government? To many in the high command, this sounded a lot like getting rid of the Imperial system, and the Emperor, altogether, possibly prosecuting him as a «war criminal.»For the Japanese leaders, one could no more get rid of the Emperor system and still be» Japan «than one could get rid of the US Constitution and still be» the United States of America. » During the summer, those who constituted the «Peace Party» of the high council (as opposed to the die-hard militarists, who still held a slight majority) sent out feelers to the then still-neutral Soviet Union to serve as possible mediators with the United States, hopefully negotiating an end-of-war situation that would give some guarantees as to the Emperor’s position.The Soviets rebuffed these advances (because they had already secretly agreed to enter the war on the side of the Allies), but the Americans were aware of these efforts, and Japanese attitudes towards the Emperor, because they had cracked the Japanese diplomatic code. No lesser figures than Winston Churchill and the US Secretary of War, Henry Stimson, had appealed to President Truman to clarify that the Emperor would be allowed to stay on board in a symbolic role. Truman rebuffed them, at the encouragement of his Secretary of State, James Byrnes, believing, it seems, that the perfidy of Pearl Harbor required them to grovel.It is not clear, of course, that this would have changed the lack of a Japanese response to the Potsdam Declaration. Even after the atomic bombings, the Japanese still tried to get clarification on the postwar role of the Emperor, dragging out hostilities another week. In the end, the Japanese did get to keep a largely-symbolic Emperor, but this was not finalized until the Occupation of Japan. 90002 90019 Waiting for the Soviets. 90020 The planned US invasion of the Japanese homeland, Operation Downfall, was not scheduled to take place until early November 1945.So, in principle, there was no great rush to drop the bombs in early August. The Americans knew that the Soviet Union had, at their earlier encouragement, agreed to renounce their Neutrality Pact with the Japanese and declare war, invading first through Manchuria. Stalin indicated to Truman this would happen around August 15th, to which Truman noted in his diary, «Fini Japs when that comes about.» Aside from cutting Japan off from its last bastion of resources, the notion of possibly being divided into distinct Allied zones of influence, as had been Germany, would possibly be more of a direct existential threat than any damage the Americans would inflict.And, in fact, we do now know that the Soviet invasion may have weighed as heavily on the Japanese high command as did the atomic bombings, if not more so. So why did not Truman wait? The official reason given after the fact was that any delay whatsoever would be interpreted as wasting time, and American lives, once the atomic bomb was available. But it may also have been because Truman, and especially his Secretary of State, Byrnes, may have hoped that the war might have ended before the Soviets had entered.The Soviets had been promised several concessions, including the island of Sakhalin and the Kuril Islands (giving them unimpeded access to the Pacific Ocean) for their entry in the war, but by late July 1945 року, the Americans were having second thoughts. As it was, once Stalin saw that Hiroshima did not provoke an immediate response from the Japanese, he had his marshals accelerate the invasion plans, invading Manchuria just after midnight, the morning of the Nagasaki bombing. 90003 90002 I find this one to be one of the most haunting — by filling in the missing structures, it contextualizes all of the «standard» Hiroshima photos of the rubble-filled wasteland.90050 «Rear view of Geibi and Sumitomo Buildings before and after bombing. Taken from Fukuya Department Store (700 meters [from Ground Zero]) looking toward center. Complete destruction of wooden buildings by blast and fire. Concrete structures stand. » In other places in the text, they usually point out that where you see a concrete structure like this, it has withstood the blast but was gutted by the fire. 90003 What should we make of these «alternatives»? Not, necessarily, that those in the past should have been clairvoyant.Or that their concerns were ours: like it or not, those involved in these choices certainly ranked Japanese civilian lives lower than those of American soldiers, as is typical in war. None of the «alternatives» come with any confidence, even today, much less for those at the time, and those making the choices were working with the requirements, uncertainties, and biases inherent to their historical and political positions. 90002 But by pointing out the alternatives that were on the table, one can see the areas of choice and discretion, the different directions that history might have gone — perhaps for better, perhaps for worse.We should see this history less as a static set of «inevitable» events, or of «easy» choices, but as a more subtle collection of options, motivations, and possible outcomes. 90003 90002 Tags: 1940s, Hiroshima, Historiography, Manhattan Project, Musings, Nagasaki, Speculation 90003 90002 90057 This entry was posted on Monday, August 3rd, 2015 at 12:53 pm and is filed under Meditations. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed. 90058 90003 90002 90061 Citation: 90062 Alex Wellerstein, «Were there alternatives to the atomic bombings ?,» 90007 Restricted Data: The Nuclear Secrecy Blog 90008, August 3, 2015 року, accessed July 11, 2020 року, http: //blog.nuclearsecrecy. com / 2015/08/03 / were-there-alternatives-to-the-atomic-bombings /. 90003 90050 .90000 N-word Pass | Know Your Meme 90001 90002 About 90003 90004 90005 N-word Pass 90006 refers to jokes about a satirical permit which grants the owner the ability to say the «n-word.» 90007 90002 Origin 90003 90004 The idea of ​​the N-word Pass is related to the «N Word Privileges» trope, which has a long history in pop culture as cataloged on the TV Tropes database. On June 13th, 2012 a listcle titled «Top 4 White People That Get The ‘N-Word’ Pass» was published on the hip-hop news site Hot97.90007 90002 Spread 90003 90004 On June 5th, 2018, Urban Dictionary user DefiningJusticeFromAssholes submitted an entry for «N-Word Pass,» defining it as «an unwritten pass that allows you to say the n-word ONCE!» (Shown below). 90007 90004 On November 12th, YouTuber Nass is Secretly a Pikmin uploaded a video a titled «The Penguins of Madagascar: Operation N-W.O.R.D.», In which Barack Obama grants an «n-word pass» (shown below). 90007 90018 90019 90004 On January 17th, 2019, Redditor lilbushplane submitted a photoshopped image featuring photographs of Barack Obama with the caption «The N-Word Pass» to / r / PewDiePieSubmissions (shown below).Within one month, the post garnered more than 5,000 points (95% upvoted) and 60 comments. 90007 90004 The following day, Redditor WinstonIsHarambe submitted a post titled «How to get N-Word Pass 2019 100% Works» to the / r / copypasta subreddit, where it gathered upwards of 6,200 points (94% upvoted) and 170 comments within 28 days . 90007 90024 Maryland High School Passes 90025 90004 On February 13th, 2019, the @TheScoop_US Twitter feed posted a video about students who were handing out «N-word passes» at the Winston Churchill High School in Potomac, Maryland (shown below).90007 90028 90029 Students at a Maryland high school were caught handing out «N-word passes.» 90007 90004 Is this just an offensive prank or is it unacceptable? pic.twitter.com/g9G41tg8Yn 90007 — THE SCOOP (@TheScoop_US) February 13, 2019 90033 90034 90004 That day, the webcomic Martian Magazine uploaded a comic in which a boy discovers an «N-word Pass» inside a Wonka chocolate bar (shown below). 90007 90034 90002 Search Interest 90003 90002 Know Your Meme Store 90003 90034 90002 External References 90003 .90000 21 Iteration | R for Data Science 90001 90002 Introduction 90003 90004 In functions, we talked about how important it is to reduce duplication in your code by creating functions instead of copying-and-pasting. Reducing code duplication has three main benefits: 90005 90006 90007 90004 It’s easier to see the intent of your code, because your eyes are drawn to what’s different, not what stays the same. 90005 90010 90007 90004 It’s easier to respond to changes in requirements. As your needs change, you only need to make changes in one place, rather than remembering to change every place that you copied-and-pasted the code.90005 90010 90007 90004 You’re likely to have fewer bugs because each line of code is used in more places. 90005 90010 90019 90004 One tool for reducing duplication is functions, which reduce duplication by identifying repeated patterns of code and extract them out into independent pieces that can be easily reused and updated. Another tool for reducing duplication is 90021 iteration 90022, which helps you when you need to do the same thing to multiple inputs: repeating the same operation on different columns, or on different datasets.In this chapter you’ll learn about two important iteration paradigms: imperative programming and functional programming. On the imperative side you have tools like for loops and while loops, which are a great place to start because they make iteration very explicit, so it’s obvious what’s happening. However, for loops are quite verbose, and require quite a bit of bookkeeping code that is duplicated for every for loop. Functional programming (FP) offers tools to extract out this duplicated code, so each common for loop pattern gets its own function.Once you master the vocabulary of FP, you can solve many common iteration problems with less code, more ease, and fewer errors. 90005 90024 Prerequisites 90025 90004 Once you’ve mastered the for loops provided by base R, you’ll learn some of the powerful programming tools provided by purrr, one of the tidyverse core packages. 90005 90002 For loops 90003 90004 Imagine we have this simple tibble: 90005 90004 We want to compute the median of each column. You 90033 could 90034 do with copy-and-paste: 90005 90004 But that breaks our rule of thumb: never copy and paste more than twice.Instead, we could use a for loop: 90005 90004 Every for loop has three components: 90005 90006 90007 90004 The 90021 output 90022: 90045 output <- vector ( "double", length (x)) 90046. Before you start the loop, you must always allocate sufficient space for the output. This is very important for efficiency: if you grow the for loop at each iteration using 90045 c () 90046 (for example), your for loop will be very slow. 90005 90004 A general way of creating an empty vector of given length is the 90045 vector () 90046 function.It has two arguments: the type of the vector ( "logical", "Integer", "double", "character", etc) and the length of the vector. 90005 90010 90007 90004 The 90021 sequence 90022: 90045 i in seq_along (df) 90046. This determines what to loop over: each run of the for loop will assign 90045 i 90046 to a different value from 90045 seq_along (df) 90046. It's useful to think of 90045 i 90046 as a pronoun, like "it". 90005 90004 You might not have seen 90045 seq_along () 90046 before. It's a safe version of the familiar 90045 1: length (l) 90046, with an important difference: if you have a zero-length vector, 90045 seq_along () 90046 does the right thing: 90005 90004 You probably will not create a zero-length vector deliberately, but it's easy to create them accidentally.If you use 90045 1: length (x) 90046 instead of 90045 seq_along (x) 90046, you're likely to get a confusing error message. 90005 90010 90007 90004 The 90021 body 90022: 90045 output [[i]] <- median (df [[i]]) 90046. This is the code that does the work. It's run repeatedly, each time with a different value for 90045 i 90046. The first iteration will run 90045 output [[1]] <- median (df [[1]]) 90046, the second will run 90045 output [[2]] <- median (df [[2]]) 90046, and so on. 90005 90010 90019 90004 That's all there is to the for loop! Now is a good time to practice creating some basic (and not so basic) for loops using the exercises below.Then we'll move on some variations of the for loop that help you solve other problems that will crop up in practice. 90005 90024 Exercises 90025 90006 90007 90004 Write for loops to: 90005 90006 90007 Compute the mean of every column in 90045 mtcars 90046. 90010 90007 Determine the type of each column in 90045 nycflights13 :: flights 90046. 90010 90007 Compute the number of unique values ​​in each column of 90045 iris 90046. 90010 90007 Generate 10 random normals from distributions with means of -10, 0, 10, and 100.90010 90019 90004 Think about the output, sequence, and body 90021 before 90022 you start writing the loop. 90005 90010 90007 90004 Eliminate the for loop in each of the following examples by taking advantage of an existing function that works with vectors: 90005 90010 90007 90004 Combine your function writing and for loop skills: 90005 90006 90007 90004 Write a for loop that 90045 prints () 90046 the lyrics to the children's song "Alice the camel". 90005 90010 90007 90004 Convert the nursery rhyme "ten in the bed" to a function.Generalise it to any number of people in any sleeping structure. 90005 90010 90007 90004 Convert the song "99 bottles of beer on the wall" to a function. Generalise to any number of any vessel containing any liquid on any surface. 90005 90010 90019 90010 90007 90004 It's common to see for loops that do not preallocate the output and instead increase the length of a vector at each step: 90005 90004 How does this affect performance? Design and execute an experiment. 90005 90010 90019 90002 For loop variations 90003 90004 Once you have the basic for loop under your belt, there are some variations that you should be aware of.These variations are important regardless of how you do iteration, so do not forget about them once you've mastered the FP techniques you'll learn about in the next section. 90005 90004 There are four variations on the basic theme of the for loop: 90005 90006 90007 Modifying an existing object, instead of creating a new object. 90010 90007 Looping over names or values, instead of indices. 90010 90007 Handling outputs of unknown length. 90010 90007 Handling sequences of unknown length.90010 90019 90024 Modifying an existing object 90025 90004 Sometimes you want to use a for loop to modify an existing object. For example, remember our challenge from functions. We wanted to rescale every column in a data frame: 90005 90004 To solve this with a for loop we again think about the three components: 90005 90006 90007 90004 90021 Output 90022: we already have the output - it's the same as the input! 90005 90010 90007 90004 90021 Sequence 90022: we can think about a data frame as a list of columns, so we can iterate over each column with 90045 seq_along (df) 90046.90005 90010 90007 90004 90021 Body 90022: apply 90045 rescale01 () 90046. 90005 90010 90019 90004 This gives us: 90005 90004 Typically you'll be modifying a list or data frame with this sort of loop, so remember to use 90045 [[90046, not 90045 [90046. You might have spotted that I used 90045 [[90046 in all my for loops: I think it's better to use 90045 [[90046 even for atomic vectors because it makes it clear that I want to work with a single element. 90005 90024 Looping patterns 90025 90004 There are three basic ways to loop over a vector.So far I've shown you the most general: looping over the numeric indices with 90045 for (i in seq_along (xs)) 90046, and extracting the value with 90045 x [[i]] 90046. There are two other forms: 90005 90006 90007 90004 Loop over the elements: 90045 for (x in xs) 90046. This is most useful if you only care about side-effects, like plotting or saving a file, because it's difficult to save the output efficiently. 90005 90010 90007 90004 Loop over the names: 90045 for (nm in names (xs)) 90046.This gives you name, which you can use to access the value with 90045 x [[nm]] 90046. This is useful if you want to use the name in a plot title or a file name. If you're creating named output, make sure to name the results vector like so: 90005 90010 90019 90004 Iteration over the numeric indices is the most general form, because given the position you can extract both the name and the value: 90005 90024 Unknown output length 90025 90004 Sometimes you might not know how long the output will be.2 \)) times as long to run. 90005 90004 A better solution to save the results in a list, and then combine into a single vector after the loop is done: 90005 90004 Here I've used 90045 unlist () 90046 to flatten a list of vectors into a single vector. A stricter option is to use 90045 purrr :: flatten_dbl () 90046 - it will throw an error if the input is not a list of doubles. 90005 90004 This pattern occurs in other places too: 90005 90006 90007 90004 You might be generating a long string.Instead of 90045 paste () 90046 ing together each iteration with the previous, save the output in a character vector and then combine that vector into a single string with 90045 paste (output, collapse = "") 90046. 90005 90010 90007 90004 You might be generating a big data frame. Instead of sequentially 90045 rbind () 90046 ing in each iteration, save the output in a list, then use 90045 dplyr :: bind_rows (output) 90046 to combine the output into a single data frame. 90005 90010 90019 90004 Watch out for this pattern.Whenever you see it, switch to a more complex result object, and then combine in one step at the end. 90005 90024 Unknown sequence length 90025 90004 Sometimes you do not even know how long the input sequence should run for. This is common when doing simulations. For example, you might want to loop until you get three heads in a row. You can not do that sort of iteration with the for loop. Instead, you can use a while loop. A while loop is simpler than for loop because it only has two components, a condition and a body: 90005 90004 A while loop is also more general than a for loop, because you can rewrite any for loop as a while loop, but you can not rewrite every while loop as a for loop: 90005 90004 Here's how we could use a while loop to find how many tries it takes to get three heads in a row: 90005 90004 I mention while loops only briefly, because I hardly ever use them.They're most often used for simulation, which is outside the scope of this book. However, it is good to know they exist so that you're prepared for problems where the number of iterations is not known in advance. 90005 90024 Exercises 90025 90006 90007 90004 Imagine you have a directory full of CSV files that you want to read in. You have their paths in a vector, 90045 files <- dir ( "data /", pattern = "\\. Csv $", full.names = TRUE) 90046, and now want to read each one with 90045 read_csv () 90046.Write the for loop that will load them into a single data frame. 90005 90010 90007 90004 What happens if you use 90045 for (nm in names (x)) 90046 and 90045 x 90046 has no names? What if only some of the elements are named? What if the names are not unique? 90005 90010 90007 90004 Write a function that prints the mean of each numeric column in a data frame, along with its name. For example, 90045 show_mean (iris) 90046 would print: 90005 90004 (Extra challenge: what function did I use to make sure that the numbers lined up nicely, even though the variable names had different lengths?) 90005 90010 90007 90004 What does this code do? How does it work? 90005 90010 90019 90002 For loops vs.functionals 90003 90004 For loops are not as important in R as they are in other languages ​​because R is a functional programming language. This means that it's possible to wrap up for loops in a function, and call that function instead of using the for loop directly. 90005 90004 To see why this is important, consider (again) this simple data frame: 90005 90004 Imagine you want to compute the mean of every column. You could do that with a for loop: 90005 90004 You realise that you're going to want to compute the means of every column pretty frequently, so you extract it out into a function: 90005 90004 But then you think it'd also be helpful to be able to compute the median, and the standard deviation, so you copy and paste your 90045 col_mean () 90046 function and replace the 90045 mean () 90046 with 90045 median () 90046 and 90045 sd () 90046: 90005 90004 Uh oh! You've copied-and-pasted this code twice, so it's time to think about how to generalise it.Notice that most of this code is for-loop boilerplate and it's hard to see the one thing (90045 mean () 90046, 90045 median () 90046, 90045 sd () 90046) that is different between the functions. 90005 90004 What would you do if you saw a set of functions like this: 90005 90004 Hopefully, you'd notice that there's a lot of duplication, and extract it out into an additional argument: 90005 90004 You've reduced the chance of bugs (because you now have 1/3 of the original code), and made it easy to generalise to new situations.90005 90004 We can do exactly the same thing with 90045 col_mean () 90046, 90045 col_median () 90046 and 90045 col_sd () 90046 by adding an argument that supplies the function to apply to each column: 90005 90004 The idea of ​​passing a function to another function is an extremely powerful idea, and it's one of the behaviours that makes R a functional programming language. It might take you a while to wrap your head around the idea, but it's worth the investment. In the rest of the chapter, you'll learn about and use the 90021 purrr 90022 package, which provides functions that eliminate the need for many common for loops.The apply family of functions in base R (90045 apply () 90046, 90045 lapply () 90046, 90045 tapply () 90046, etc) solve a similar problem, but purrr is more consistent and thus is easier to learn. 90005 90004 The goal of using purrr functions instead of for loops is to allow you to break common list manipulation challenges into independent pieces: 90005 90006 90007 90004 How can you solve the problem for a single element of the list? Once you've solved that problem, purrr takes care of generalising your solution to every element in the list.90005 90010 90007 90004 If you're solving a complex problem, how can you break it down into bite-sized pieces that allow you to advance one small step towards a solution? With purrr, you get lots of small pieces that you can compose together with the pipe. 90005 90010 90019 90004 This structure makes it easier to solve new problems. It also makes it easier to understand your solutions to old problems when you re-read your old code. 90005 90024 Exercises 90025 90006 90007 90004 Read the documentation for 90045 apply () 90046.In the 2d case, what two for loops does it generalise? 90005 90010 90007 90004 Adapt 90045 col_summary () 90046 so that it only applies to numeric columns You might want to start with an 90045 is_numeric () 90046 function that returns a logical vector that has a TRUE corresponding to each numeric column. 90005 90010 90019 90002 The map functions 90003 90004 The pattern of looping over a vector, doing something to each element and saving the results is so common that the purrr package provides a family of functions to do it for you.There is one function for each type of output: 90005 90408 90007 90045 map () 90046 makes a list. 90010 90007 90045 map_lgl () 90046 makes a logical vector. 90010 90007 90045 map_int () 90046 makes an integer vector. 90010 90007 90045 map_dbl () 90046 makes a double vector. 90010 90007 90045 map_chr () 90046 makes a character vector. 90010 90429 90004 Each function takes a vector as input, applies a function to each piece, and then returns a new vector that's the same length (and has the same names) as the input.The type of the vector is determined by the suffix to the map function. 90005 90004 Once you master these functions, you'll find it takes much less time to solve iteration problems. But you should never feel bad about using a for loop instead of a map function. The map functions are a step up a tower of abstraction, and it can take a long time to get your head around how they work. The important thing is that you solve the problem that you're working on, not write the most concise and elegant code (although that's definitely something you want to strive towards!).90005 90004 Some people will tell you to avoid for loops because they are slow. They're wrong! (Well at least they're rather out of date, as for loops have not been slow for many years.) The chief benefits of using functions like 90045 map () 90046 is not speed, but clarity: they make your code easier to write and to read. 90005 90004 We can use these functions to perform the same computations as the last for loop. Those summary functions returned doubles, so we need to use 90045 map_dbl () 90046: 90005 90004 Compared to using a for loop, focus is on the operation being performed (i.e. 90045 mean () 90046, 90045 median () 90046, 90045 sd () 90046), not the bookkeeping required to loop over every element and store the output. This is even more apparent if we use the pipe: 90005 90004 There are a few differences between 90045 map _ * () 90046 and 90045 col_summary () 90046: 90005 90024 Shortcuts 90025 90004 There are a few shortcuts that you can use with 90045 .f 90046 in order to save a little typing. Imagine you want to fit a linear model to each group in a dataset.The following toy example splits up the 90045 mtcars 90046 dataset into three pieces (one for each value of cylinder) and fits the same linear model to each piece: 90005 90004 The syntax for creating an anonymous function in R is quite verbose so purrr provides a convenient shortcut: a one-sided formula. 90005 90004 Here I've used 90045. 90046 as a pronoun: it refers to the current list element (in the same way that 90045 i 90046 referred to the current index in the for loop). 90005 90004 When you're looking at many models, you might want to extract a summary statistic like the \ (R ^ 2 \).To do that we need to first run 90045 summary () 90046 and then extract the component called 90045 r.squared 90046. We could do that using the shorthand for anonymous functions: 90005 90004 But extracting named components is a common operation, so purrr provides an even shorter shortcut: you can use a string. 90005 90004 You can also use an integer to select elements by position: 90005 90024 Base R 90025 90004 If you're familiar with the apply family of functions in base R, you might have noticed some similarities with the purrr functions: 90005 90408 90007 90004 90045 lapply () 90046 is basically identical to 90045 map () 90046, except that 90045 map () 90046 is consistent with all the other functions in purrr, and you can use the shortcuts for 90045.f 90046. 90005 90010 90007 90004 Base 90045 sapply () 90046 is a wrapper around 90045 lapply () 90046 that automatically simplifies the output. This is useful for interactive work but is problematic in a function because you never know what sort of output you'll get: 90005 90506 90045 x1 <- list ( c (0.27, 0.37, 0.57, 0.91, 0.20), c (0.90, 0.94, 0.66, 0.63, 0.06), c (0.21, 0.18, 0.69, 0.38, 0.77) ) x2 <- list ( c (0.50, 0.72, 0.99, 0.38, 0.78), c (0.93, 0.21, 0.65, 0.13, 0.27), c (0.39, 0.01, 0.38, 0.87, 0.34) ) threshold <- function (x, cutoff = 0.8) x [x> cutoff] x1%>% sapply (threshold)%>% str () #> List of 3 #> $: Num 0.91 #> $: Num [1: 2] 0.9 0.94 #> $: Num (0) x2%>% sapply (threshold)%>% str () #> Num [1: 3] 0.99 0.93 0.87 90046 90509 90010 90007 90004 90045 vapply () 90046 is a safe alternative to 90045 sapply () 90046 because you supply an additional argument that defines the type. The only problem with 90045 vapply () 90046 is that it’s a lot of typing: 90045 vapply (df, is.numeric, logical (1)) 90046 is equivalent to 90045 map_lgl (df, is.numeric) 90046. One advantage of 90045 vapply () 90046 over purrr’s map functions is that it can also produce matrices — the map functions only ever produce vectors. 90005 90010 90429 90004 I focus on purrr functions here because they have more consistent names and arguments, helpful shortcuts, and in the future will provide easy parallelism and progress bars. 90005 90024 Exercises 90025 90006 90007 90004 Write code that uses one of the map functions to: 90005 90006 90007 Compute the mean of every column in 90045 mtcars 90046.90010 90007 Determine the type of each column in 90045 nycflights13 :: flights 90046. 90010 90007 Compute the number of unique values ​​in each column of 90045 iris 90046. 90010 90007 Generate 10 random normals from distributions with means of -10, 0, 10, and 100. 90010 90019 90010 90007 90004 How can you create a single vector that for each column in a data frame indicates whether or not it’s a factor? 90005 90010 90007 90004 What happens when you use the map functions on vectors that are not lists? What does 90045 map (1: 5, runif) 90046 do? Why? 90005 90010 90007 90004 What does 90045 map (-2: 2, rnorm, n = 5) 90046 do? Why? What does 90045 map_dbl (-2: 2, rnorm, n = 5) 90046 do? Why? 90005 90010 90007 90004 Rewrite 90045 map (x, function (df) lm (mpg ~ wt, data = df)) 90046 to eliminate the anonymous function.90005 90010 90019 90002 Dealing with failure 90003 90004 When you use the map functions to repeat many operations, the chances are much higher that one of those operations will fail. When this happens, you’ll get an error message, and no output. This is annoying: why does one failure prevent you from accessing all the other successes? How do you ensure that one bad apple does not ruin the whole barrel? 90005 90004 In this section you’ll learn how to deal with this situation with a new function: 90045 safely () 90046.90045 safely () 90046 is an adverb: it takes a function (a verb) and returns a modified version. In this case, the modified function will never throw an error. Instead, it always returns a list with two elements: 90005 90006 90007 90004 90045 result 90046 is the original result. If there was an error, this will be 90045 NULL 90046. 90005 90010 90007 90004 90045 error 90046 is an error object. If the operation was successful, this will be 90045 NULL 90046. 90005 90010 90019 90004 (You might be familiar with the 90045 try () 90046 function in base R.It’s similar, but because it sometimes returns the original result and it sometimes returns an error object it’s more difficult to work with.) 90005 90004 Let’s illustrate this with a simple example: 90045 log () 90046: 90005 90004 When the function succeeds, the 90045 result 90046 element contains the result and the 90045 error 90046 element is 90045 NULL 90046. When the function fails, the 90045 result 90046 element is 90045 NULL 90046 and the 90045 error 90046 element contains an error object.90005 90004 90045 safely () 90046 is designed to work with map: 90005 90004 This would be easier to work with if we had two lists: one of all the errors and one of all the output. That’s easy to get with 90045 purrr :: transpose () 90046: 90005 90004 It’s up to you how to deal with the errors, but typically you’ll either look at the values ​​of 90045 x 90046 where 90045 y 90046 is an error, or work with the values ​​of 90045 y 90046 that are ok: 90005 90004 Purrr provides two other useful adverbs: 90005 90408 90007 90004 Like 90045 safely () 90046, 90045 possibly () 90046 always succeeds.It’s simpler than 90045 safely () 90046, because you give it a default value to return when there is an error. 90005 90010 90007 90004 90045 quietly () 90046 performs a similar role to 90045 safely () 90046, but instead of capturing errors, it captures printed output, messages, and warnings: 90005 90010 90429 90002 Mapping over multiple arguments 90003 90004 So far we’ve mapped along a single input. But often you have multiple related inputs that you need iterate along in parallel.That’s the job of the 90045 map2 () 90046 and 90045 pmap () 90046 functions. For example, imagine you want to simulate some random normals with different means. You know how to do that with 90045 map () 90046: 90005 90004 What if you also want to vary the standard deviation? One way to do that would be to iterate over the indices and index into vectors of means and sds: 90005 90004 But that obfuscates the intent of the code. Instead we could use 90045 map2 () 90046 which iterates over two vectors in parallel: 90005 90004 90045 map2 () 90046 generates this series of function calls: 90005 90004 90687 90005 90004 Note that the arguments that vary for each call come 90033 before 90034 the function; arguments that are the same for every call come 90033 after 90034.90005 90004 Like 90045 map () 90046, 90045 map2 () 90046 is just a wrapper around a for loop: 90005 90004 You could also imagine 90045 map3 () 90046, 90045 map4 () 90046, 90045 map5 () 90046, 90045 map6 () 90046 etc, but that would get tedious quickly. Instead, purrr provides 90045 pmap () 90046 which takes a list of arguments. You might use that if you wanted to vary the mean, standard deviation, and number of samples: 90005 90004 That looks like: 90005 90004 90716 90005 90004 If you do not name the list’s elements, 90045 pmap () 90046 will use positional matching when calling the function.That’s a little fragile, and makes the code harder to read, so it’s better to name the arguments: 90005 90004 That generates longer, but safer, calls: 90005 90004 90725 90005 90004 Since the arguments are all the same length, it makes sense to store them in a data frame: 90005 90506 90045 params <- tribble ( ~ Mean, ~ sd, ~ n, 5, 1, 1, 10, 5, 3, -3, 10, 5 ) params%>% pmap (rnorm) #> [[1]] #> [1] 6.02 #> #> [[2]] #> [1] 8.68 18.29 6.13 #> #> [[3]] #> [1] -12.24 -5.76 -8.93 -4.22 8.80 90046 90509 90004 As soon as your code gets complicated, I think a data frame is a good approach because it ensures that each column has a name and is the same length as all the other columns. 90005 90024 Invoking different functions 90025 90004 There’s one more step up in complexity — as well as varying the arguments to the function you might also vary the function itself: 90005 90004 To handle this case, you can use 90045 invoke_map () 90046: 90005 90004 90744 90005 90004 The first argument is a list of functions or character vector of function names.The second argument is a list of lists giving the arguments that vary for each function. The subsequent arguments are passed on to every function. 90005 90004 And again, you can use 90045 tribble () 90046 to make creating these matching pairs a little easier: 90005 90506 90045 sim <- tribble ( ~ F, ~ params, "Runif", list (min = -1, max = 1), "Rnorm", list (sd = 5), "Rpois", list (lambda = 10) ) sim%>% mutate (sim = invoke_map (f, params, n = 10)) 90046 90509 90002 Walk 90003 90004 Walk is an alternative to map that you use when you want to call a function for its side effects, rather than for its return value.You typically do this because you want to render output to the screen or save files to disk — the important thing is the action, not the return value. Here’s a very simple example: 90005 90004 90045 walk () 90046 is generally not that useful compared to 90045 walk2 () 90046 or 90045 pwalk () 90046. For example, if you had a list of plots and a vector of file names, you could use 90045 pwalk () 90046 to save each file to the corresponding location on disk: 90005 90004 90045 walk () 90046, 90045 walk2 () 90046 and 90045 pwalk () 90046 all invisibly return 90045.x 90046, the first argument. This makes them suitable for use in the middle of pipelines. 90005 90002 Other patterns of for loops 90003 90004 Purrr provides a number of other functions that abstract over other types of for loops. You’ll use them less frequently than the map functions, but they’re useful to know about. The goal here is to briefly illustrate each function, so hopefully it will come to mind if you see a similar problem in the future. Then you can go look up the documentation for more details.90005 90024 Predicate functions 90025 90004 A number of functions work with 90021 predicate 90022 functions that return either a single 90045 TRUE 90046 or 90045 FALSE 90046. 90005 90004 90045 keep () 90046 and 90045 discard () 90046 keep elements of the input where the predicate is 90045 TRUE 90046 or 90045 FALSE 90046 respectively: 90005 90004 90045 some () 90046 and 90045 every () 90046 determine if the predicate is true for any or for all of the elements. 90005 90004 90045 detect () 90046 finds the first element where the predicate is true; 90045 detect_index () 90046 returns its position.90005 90004 90045 head_while () 90046 and 90045 tail_while () 90046 take elements from the start or end of a vector while a predicate is true: 90005 90024 Reduce and accumulate 90025 90004 Sometimes you have a complex list that you want to reduce to a simple list by repeatedly applying a function that reduces a pair to a singleton. This is useful if you want to apply a two-table dplyr verb to multiple tables. For example, you might have a list of data frames, and you want to reduce to a single data frame by joining the elements together: 90005 90004 Or maybe you have a list of vectors, and want to find the intersection: 90005 90506 90045 vs <- list ( c (1, 3, 5, 6, 10), c (1, 2, 3, 7, 8, 10), c (1, 2, 3, 4, 8, 9, 10) ) vs%>% reduce (intersect) #> [1] 1 3 10 90046 90509 90004 The reduce function takes a «binary» function (i.e. a function with two primary inputs), and applies it repeatedly to a list until there is only a single element left. 90005 90004 Accumulate is similar but it keeps all the interim results. You could use it to implement a cumulative sum: 90005 90024 Exercises 90025 90006 90007 90004 Implement your own version of 90045 every () 90046 using a for loop. Compare it with 90045 purrr :: every () 90046. What does purrr’s version do that your version does not? 90005 90010 90007 90004 Create an enhanced 90045 col_summary () 90046 that applies a summary function to every numeric column in a data frame.90005 90010 90007 90004 A possible base R equivalent of 90045 col_summary () 90046 is: 90005 90004 But it has a number of bugs as illustrated with the following inputs: 90005 90004 What causes the bugs? 90005 90010 90019 .90000 How I Learned to Stop Worrying and Love the Atomic Spaceship • Damn Interesting 90001 90002 90003 The year was 1957. The power of the atom had been unleashed upon the world. Technology⁠-along with just about everything else⁠-was booming. Safe, plentiful nuclear energy promised to be too cheap to meter, and radioactive waste seemed only a minor concern. It was an age of optimism and naiveté; a time of action without consequences. 90004 90003 Though man was the master of the Earth, only once had he managed to explore beyond the confines of the atmosphere, in the form of a beachball-sized spacecraft called Sputnik.Werner von Braun’s rocket men had drawn up plans for spacecraft that would launch humans into orbit, but even then it was clear that inefficient chemical rockets would allow only a few to enter space; the rest of mankind would be mere spectators. Fresh from their success with the atomic bomb, a small team of Manhattan Project physicists gathered to try and change all that. Working in secret within the brand new Advanced Research Projects Agency (ARPA, now called DARPA), they designed and tested an enormously ambitious nuclear spaceship concept that would have made everything the Soviets and NASA were doing seem like hobby rockets in comparison.The codename was 90006 Project Orion 90007. 90004 90003 Project Orion was intended to harness nuclear energy in its rawest form: by detonating a series of nuclear bombs in rapid succession to propel enormous spaceships from the Earth into the heavens. The largest of the Orions was to be seven million tons⁠-more than 7,000 times more massive than the Space Shuttle⁠- and powerful enough to launch a small city. Provided sufficient numbers of bombs, an Orion spaceship theoretically could have reached 1 / 10th the speed of light, enabling interstellar travel.The motto of Project Orion was «Mars in 1965, Saturn in 1970.» 90004 90003 When General Atomics (GA) pitched the idea behind Project Orion to ARPA in 1958 the concept of a nuclear-propelled spaceship was nothing new. Pulp science-fiction invoked a vague «atomic drive» as early as the mid-1930s. Yet until the Manhattan Project, atomic energy was the stuff of the future. That all changed in late August 1945 when the United States opened the nuclear Pandora’s box, and the entire world stood aghast.As the dust was still settling over Hiroshima and Nagasaki, scientists and engineers almost immediately began working to harness nuclear energy for non-destructive purposes. Atoms for Peace exported civilian nuclear reactors across the world, and few companies stood to gain as much from increased use of nuclear technology as GA. The California-based company positioned itself as one of the gatekeepers of the Atomic Age, and in the process they snapped up many of the brilliant Manhattan Project minds.90004 90003 Two of those men⁠-physicists Stanislaw Ulam and Freeman Dyson⁠-came to GA with an Earth-shaking idea. Intoxicated by the heady aroma of a new Age, GA hired Ulam and Dyson to study their idea for the nuclear spaceship. On its face, the very idea of ​​nuclear explosions being harnessed for useful purposes seemed ridiculous. Many GA employees had seen the awesome specter of mushroom clouds first-hand, and the entire world had witnessed the destruction wreaked upon Japan. But Ulam and Dyson reasoned that properly shaped nuclear explosions could yield most of their energy to the propulsion of a spacecraft while leaving the ship and its occupants intact.90004 90003 The fundamental design of a Project Orion spacecraft consisted of four parts: a payload of nuclear bombs, propellant, a pusher plate, and a spaceship. During launch from the Earth’s surface, the nuclear bombs would be rapidly detonated behind the Orion craft at pre-calculated distances. A disk of propellant material attached to each bomb would be vaporized to a plasma by the explosion. This plasma would expand into a cigar shape while being propelled at astounding velocities toward a heavy metal plate at the base of the ship.That pusher plate, attached to enormous hydraulic shock absorbers, would absorb the momentum of the plasma and propel the Orion spaceship forward. 90004 90017 Time-lapse image sequence running from bottom to top of the flight of «Hot Rod» 90003 Project Orion was fueled by the raw intellectual prowess and unerring faith in technology held by some of the world’s most brilliant people. Its budget was tiny compared to that of the defense conglomerate General Dynamics in which it existed. Nevertheless, within a year the Orion team had completed calculations that indicated the project was feasible.In the next few months, a series of scale-model experiments called «putt-putts» were conducted with the high-powered chemical explosive C4. The first few designs were destroyed, but in November 1959 a putt-putt called Hot Rod flew to an altitude of 100 meters. The flight was surprisingly stable, and the craft nearly unscathed, lending strong evidence to the feasibility of the entire project. 90004 90003 A full-size Orion vehicle would have had a mass of 4,000 tons, ⁠- about 40 times that of the Space Shuttle⁠- and would include a «pusher plate» about 1-meter thick at the center.This solid mass of metal served to reflect the Orion craft away from the nuclear explosions, while at the same time protecting the passengers from the neutron radiation. The enormous shock absorbers between the pusher plate and the crew module would then distribute the 10,000 G’s of each nuclear blast to something much more comfortable for Orion’s passengers. In fact, an Orion launch would probably be much more comfortable than a conventional chemical rocket because of the sheer mass of the vehicle.90004 90003 Consider the launch of a hypothetical 4,000 ton Orion spaceship propelled by four-kiloton bombs. The need for protective eye wear would immediately become evident as the enormous ship would become engulfed in a fireball more intensely bright than the surface of the sun. A rapid series of blossoming explosions would push the first expanding ball of plasma skyward, though the ship would be completely invisible against the blinding glare. Within one minute, the chain of blasts would start to become visibly separate as a new flash of light would appear every few thousand feet.This pace would continue, gradually slowing until Orion reached orbit several minutes later. The final flash would then expand into the cap of a hundred-mile-long string of enormous, fiery pearls that would seem to ooze out of the ground into the atmosphere and arch gracefully into space. For observers at a safe distance, the entire launch would be completely silent. But when the pressure wave reached them a few seconds after the Orion completed its launch, the long series of thundering explosions would have sounded like the coming of the Apocalypse.90004 90003 Perhaps, then, it is small surprise that the launch of the Orion was the greatest technical hurdle to its success. A single Orion launch would have left a trail of fallout across a tremendous swath of the land or sea, the radiation from its bombs would have charged the ionosphere and the Van Allen belts around the Earth, and its series of electromagnetic pulses would have destroyed all electronics within hundreds of miles of the launch site with the larger designs. It became clear to the GA physicists that solving these problems was crucial for the viability of the Project.90004 90003 While they worked feverishly at overcoming the technical challenges, political forces were moving against the Project. The young NASA had the ear of the President, and parts of the agency fiercely opposed Project Orion. Werner von Braun, the German head of NASA’s manned space rocket effort was supportive of the Project and visited GA several times to confer with managers and physicists. Collaborations involving smaller Orions launched atop modified Saturn V vehicles were proposed by both parties.In early 1963 it seemed that NASA might support Orion, but the agency’s administration never came around to the idea and Project Orion was soon orphaned. 90004 90028 Rendering of an Orion launch by Rhys Taylor 90003 After years of steadily declining budgets, 1965 brought the end of Project Orion. A powerful quartet of forces had aligned against it including the Defense Department, NASA, supporters of Nuclear Test Ban and Outer Space treaties, and much of the scientific establishment. While opposition from agencies and individuals may have been the immediate cause of its cancellation, the ultimate cause of its demise was probably the inability for most people to grasp how such a vehicle could ever be made safe.In addition, it was clear that every launch of an Orion would have had a massive impact on the environment. 90004 90003 Though Project Orion is long dead, the idea of ​​a pulse-detonation nuclear spaceship is still alive. To some, the idea of ​​discarding our flimsy aluminum / carbon rockets in favor of such battleship-sized behemoths is deeply romantic. More pragmatic supporters suggest a version of Orion assembled in orbit, thus avoiding most of the environmental dangers. Some have also suggested using massive, unmanned Orion craft mounted to the surface of an asteroid to push it away from collision course with Earth.One thing is certain: Orion and its nuclear-pulsed propulsion is one of the only technologies capable of reaching the speeds necessary for real-live humans to explore the outer solar system. Moreover, if mankind wishes to penetrate the frontier of interstellar space, this mothballed Atomic-Age technology may be our best chance. 90004 .