- " Now, on October 25, 1985, he [Doc] was ready for fulfillment. He had worked out every element of his time-travel theory until it was perfect. By the end of the century, scientists and historians would be using his device to explore the future and past, and through this exploration, work to improve the present. His view of time as a dimension was summed up in the simple explanation he once gave to the editor of the Hill Valley newspaper. "I think of time as spherical and unending," he said. "Like the skin of an orange. A change in the texture at any point will be felt over the entire skin. The future affects the past and present, just as the past and present affect the future." / "But the past is over and done with," the editor replied. "How can it be affected?" / "That's just my point," Doc Brown had retorted. "The past isn't over and done with. It's still there. And once we find a way to penetrate it, we'll be able to change things that may happen tomorrow." / The editor didn't buy it, but he printed the interview anyway. Residents of Hill Valley either ignored the article or complained that valuable space had been wasted printing the ravings of a madman. / Such unfavorable publicity once hurt, but now that was all behind him. "If all goes well..." he murmured as he began to prepare for the evening's work. "
- —From Back to the Future by George Gipe (quote, pages 26 and 27)
Time travel was the process of traveling through time, and was done with a time machine.
In 1943, Emmett Brown was working as a professor at the California Institute of Technology. He convinced the president of CalTech, Robert Millikan, to get him an interview with the government for the top secret project for which they were recruiting. After a disastrous interview where he pretended the house of his landlady was his own, Emmett walked back to his apartment. He was surprised to see Vannevar Bush and J. Robert Oppenheimer there waiting for him. They told him that his unusual method of thinking was exactly what they were looking for, and hired him to work on the Manhattan Project.
While working on the project, Emmett became an expert in the field of nuclear physics. He also was prone to come up with wild hypotheses, which Major General Leslie Groves called "flights of fancy". However, Emmett left a lasting impression on Groves, who believed that if anyone could invent time travel, he could.
On November 5, 1955, Doc Brown came up with the idea of a device that would make time travel possible after slipping and bumping his head while standing on his toilet to hang a clock. The idea came to him in a vision he had after being knocked out. He drew an inverted Y-shape with wires and stated "flux compression". He also performed some mild calculations on the paper.
Temporal field time machine prototypes
By the 1960s, Doc utilized his ideas of flux compression to develop a time machine that was capable of sending objects through time, but only during the lifespan of the device. The time machine, known as the temporal field capacitor, was only useful for sending objects into the future. Sending an object even a few minutes into the past caused a buildup of flux energy. If an object was sent any further back than that, the arrival of the object would overheat the capacitor and start an electrical fire.
On October 24, 1962, Leslie Groves and Colonel Lomax visited Doc, on behalf of the United States military, as they were looking for a way to travel back in time to prevent the Cuban Missile Crisis from ever occurring. Doc told them about his invention, as he needed funding for his other inventions. He later had worries that he could be ushering in an arms race through time, coupled with his regrets about ushering in the nuclear arms race of the Cold War through his participation in the Manhattan Project.
The next day, he wrote himself a letter about his plans, and purposefully sent the letter back several months in the past, to August 1, when he knew that he and his dog, Copernicus, would be safe asleep in his fireproof garage. The Brown family mansion burned down, and the military personnel came and left in the new timeline without ever talking to Doc. Doc used the insurance money to fund the rebuilding of the temporal field capacitor, as well as his future inventions.
The invention of the temporal field capacitor was a necessary step towards the invention of the flux capacitor, which was the device that made time travel possible, as it solved the problem of the excess flux energy when traveling to the past.
After Doc had received the insurance money for his family mansion, he built an improved version of the temporal field capacitor called the temporal field generator mark II. Like the original, it could only send objects through time during the time period in which the device had been turned on. However, it improved upon the original device in that it could transport larger objects through time. It could also send objects many years into the past without causing an electrical fire. However, Doc was careful not to use this device too much, as one test nearly resulted in the destruction of the fabric of reality.
The first DeLorean time machine
On October 2, 1982, Marty McFly sneaked into Doc's garage to get the interocitor tubes that Doc had purchased under the name of his company, ELB Enterprises. Marty had to solve the riddles of the various traps that Doc had set up to prevent people from entering his garage. Due to Marty's ingenuity, as well as his honesty in admitting that he had sneaked in to get the tubes, Doc hired Marty as his assistant.
This allowed Doc to not have to worry about the care of his garage and his dog, Einstein. He was able to work on experiments in his secret lab. Doc didn't reveal the location to this lab to anyone, including his assistant. He even went to extreme lengths to keep it a secret, registering the building under his birth name, Von Braun.
Doc wanted to use the DeLorean because its stainless steel construction would help with the dispersal of flux energy. In addition, Doc had made a deal with terrorists from Libya. They would steal a box containing plutonium, and in exchange, Doc would build a nuclear weapon for them. Instead, once they gave Doc the plutonium, he sent them a useless shell that simply contained the pinball machine parts.
By 1985, Doc Brown had finished his DeLorean time machine, which was the first time machine capable of transporting living beings through time. It utilized the flux capacitor, as well as a nuclear reactor that used plutonium pellets to generate 1.21 jigowatts of electricity. This allowed it to break the time barrier in what was called temporal displacement. It traveled along the space-time continuum, bringing the occupant safely to any point in time, but not in space. The original DeLorean time machine could only arrive at the same location from which it departed.
The first successful test of the DeLorean time machine occurred at 1:20:00 am on October 26, 1985 at the Twin Pines Mall. Doc sent Einstein one minute into the future. After the successful test, he planned to travel to 2010. However the Libyan terrorists managed to track Doc down, and shot him.
Marty McFly, while trying to outrun the terrorists, accidentally traveled to November 5, 1955, the day that Doc came up with the idea for the flux capacitor. He accidentally prevented the moment that his mother and father fell in love, which made a ripple in space-time, and led to his brother and sister slowly fading out of existence as the ripple caught up to the dates of their birth. Marty, being the youngest, was effected last. Since he was also a time traveler, a time bubble was formed around him when he entered the past, which also temporarily protected him from the ripple effect.
Marty had to convince his father, George McFly, to stand up to the high school bully Biff Tannen, in order to convince his mother, Lorraine Baines, to choose him rather than Biff. The plan succeeded, and on November 12, 1955, the couple fell in love at the Enchantment Under the Sea dance, as they did in the original timeline.
Marty gave Doc's 1955 counterpart a letter warning him of his death, however he tore it up. Ultimately, Doc's 1955 counterpart was able to hook a cable up to the clock tower on the Hill Valley Courthouse, which was hit by lightning that night. The lightning rod on the DeLorean hit the cable at the moment of the lightning strike, powering the nuclear reactor and successfully sending Marty back 1985, ten minutes before he left.
In the new timeline, Doc revealed that he taped the letter back together, and wore a bulletproof vest, enabling him to survive the shooting. Doc left Marty at home that night, and accomplished his original goal, by becoming the first person to travel to the future.
The next morning, Marty woke up to discover that more things had changed in the new timeline. Due to his newfound courage thanks to Marty's guidance, George McFly was a successful writer, and his mom was more confident in herself. Biff no longer rode on George's coat-tails, forcing him to write reports for him to advance his career. Because of this, Biff now ran his own auto detailing business, and George was a client. Marty now owned the 4x4 truck that he had dreamed of owning, and had made plans to go with his girlfriend to the lake.
Doc's trip to the future brought him to August 8, 2015, where he saw two inventions that could improve his DeLorean time machine. The Mr. Fusion nuclear reactor, which was powered by waste, could be used to replace the existing nuclear reactor, as plutonium pellets were hard to come by. In addition, getting a hover conversion would allow the DeLorean to travel more easily, as there would be no need for roads.
He entered the DeLorean in the Hill Valley 1980s Car Expo, and won first place, which entitled him to 10% off a hover conversion at Goldie Wilson Hover Conversion Systems. He searched the internet at the Hill Valley Public Library for prices of valuable items to find out what would be the most valuable investment. Finding what he was searching for, he left the library, entered the date April 18, 1938 into the time circuits, and headed towards his destination.
He arrived two miles outside of Hill Valley, parked the DeLorean behind a billboard advertising Studebakers, and headed into town. At a shop in Courthouse Square, he used one his silver dollar heirlooms for his purchase. He then headed back to the DeLorean, and then traveled back to 2015.
Once there, he went to Southby's Auction House to sell a near mint first issue of Action Comics for $2,500,000. He then headed back to the DeLorean, where he had stored several more. With his investment, Doc had surmised that he had managed to set him self up financially for life. He then took off in the DeLorean, which had been successfully hover converted and had the Mr. Fusion unit installed.
He established false credentials for himself in 2015 under the name Leroy Brown. Under the pseudonym Leroy Brown, Doc opened an account at the bank. He put his comic collection in a safety deposit box for safe keeping, in case he found himself in a situation where he needed extra money.
While in the future, Doc discovered that Marty's son was framed by Griff Tannen for the robbery of the Hill Valley Payroll Substation. This set up a chain of events that led to the imprisonment of Marty's daughter, as well as her suicide. Doc traveled back to November 13, 1985 to pick up Marty, just as Jennifer and Marty were going to head to the lake, so he could help fix the future for his children.
They traveled to October 21, 2015. Marty posed as his son, and he succeeded in stopping the robbery. Griff Tannen and his gang instead crashed into the Courthouse Mall, after chasing Marty on hoverboards around Courthouse Square, and were arrested.
However, before they headed back to 1985, Biff Tannen stole the DeLorean time machine. He took a Grays Sports Almanac, detailing every sporting event from 1950 to 2000, back to 1955 to make his younger self rich.
Biff wasn't sure how to operate the time machine, so he hit the time circuits with his cane. This caused the time circuits to malfunction, and Biff ended up traveling to the past once he reached 88 mph. However, the malfunctioning time circuits sent him farther than possible with the limited amount of digits currently available to input for the year.
Biff found himself in the past, during a time when the land that would be Hill Valley was under the ocean, and dinosaurs roamed the Earth. He encountered a velociraptor, which stole the Blast from the Past bag containing the Grays Sports Almanac. Biff hit the raptor in the head with his cane, retrieved the bag, and traveled forward in time to November 12, 1955.
Biff gave his 1955 counterpart the almanac. After spending time in 1955 revisiting his youth, Biff traveled back to 2015, dropping the DeLorean off where he left it. However, his actions in the past had caused him to no longer live to be an old man, and he began to fade from existence. Marty and Doc went back to the DeLorean with Jennifer and Einstein, so they could go back to 1985, not knowing that Biff had changed the past.
They found themselves in an alternate reality where Biff controlled Hill Valley, Marty was sent to a boarding school in Switzerland, and Doc was committed to an asylum. Doc found the tip of Biff's cane in the DeLorean, and realized that Biff had stolen the DeLorean to change time. He spotted the almanac in Biff's pocket in an old photograph he found at the closed Hill Valley Public Library, and realized that he had taken it from 2015 to the past to make himself rich.
Marty then went to Biff Tannen's Pleasure Paradise Casino & Hotel to find out the moment where he got the almanac. After getting the information, Doc and Marty traveled to November 21, 1955. They had to be careful not to let their younger selves see them, as there were now two versions of both of them in that time period. They were able to successfully get the almanac back and burn it. However, the DeLorean was hit by a bolt of lightning in the air, and was sent spinning on its axis up to 88 miles per hour. Due to the malfunctioning time circuits, it was sent back to January 1, 1885 with Doc inside.
A Western Union man showed up, giving Marty a letter that his office had received seventy years ago with instructions to deliver it to Marty at his exact location on November 12, 1955. Marty discovered that Doc ended up in the Old West, and that he had left the DeLorean in the Delgado Mine.
While retrieving the DeLorean, Marty discovered Doc's tombstone at Boot Hill Cemetery. With the help of Doc's 1955 counterpart, he was able to fix the DeLorean, which needed repair due to the lightning strike as well as decades of disuse while buried in the mine.
When Marty traveled back to 1885 to save Doc, he discovered that Doc fell in love with a woman named Clara Clayton. Doc ultimately ended up saving her life with the hoverboard that Marty had kept from 2015. Marty traveled back to 1985, and the DeLorean was destroyed by a diesel locomotive upon its arrival. Doc and Clara remained in 1885.
Trying to return to the 20th century
Doc was happy in 1885, as his job as the town blacksmith allowed him to conduct scientific experiments, but he didn't have to worry about being tempted with altering the space-time continuum. However, Clara wanted to travel through time. She had seen her mother struggle with fighting her rebellious nature to present herself as a proper 19th century housewife, and she didn't want that life for herself. While Doc had found a happy life in the past, she wondered if she would have been happier in his time period, where she would be allowed by society to pursue her interest in science.
When Doc and Clara had their two sons, Jules and Verne, Clara saw how happy he was reading them stories and telling them tales of his adventures. She didn't want to upset his happiness, but she was becoming less happy herself as time went on, as his stories made her want to travel to the future even more.
In the 1890s, Doc began to become homesick for his own time. He wanted to visit Marty and pick up his dog, Einstein. He began to build a time machine out of a steam locomotive. He was initially unsuccessful with his experiments to generate the amount of electricity needed for time travel. However, he was able to use the technology from the hoverboard that was left behind to create a frictionless dynamo that was able to store multiples of the 1.21 jigowatts needed to power the flux capacitor.
So, he paid some railroad workers to set up 50 yards of track and continued building the train. In 1893, he had deemed the train finished, but feared telling Clara the news. He didn't know that she wanted to travel to the future so badly, and was worried about making her unhappy just to please him.
Clara eventually told Emmett that she knew that he was inventing another time machine, telling him that he couldn't hide anything from her. She said that she would be happy to travel to the future with him and their sons. Doc, feeling his burden being lifted, decided that it was time to attempt to travel back to the future.
On June 12, 1893, the Brown family attempted to travel in the Jules Verne train to 1985. Doc calculated that 50 yards would be enough to reach 88 m.p.h, since he had improved the performance of the presto logs used to heat the boiler of the steam engine. The trip failed however, as the train didn't achieve temporal displacement, and crashed.
Doc had intended to give up his quest for time travel at that point, as he was happy in the 19th century, and didn't want to put his family in unnecessary risk. However, Clara finally told him that she had wanted to travel to the future ever since she found out about the DeLorean time machine. Time travel wasn't just his dream, it was hers too. Jules and Verne also told him that they wanted to go as well. Since his family wanted to travel through time so badly, Doc decided to try another approach towards accomplishing time travel.
The steam time car
After seeing a Steam tricycle driver driving a Serpollet steam tricycle, Doc decided to use one as a time machine. He used the flux capacitor, the frictionless dynamo, and the time circuits from the prototype Jules Verne Train in his steam time car. He had intended to travel to 2015 to pick up everything he needed to finish the Jules Verne train.
However, the stresses of space-time and the temperature variation would wreak havoc on the cast-iron frame of the steam time car. In addition, the car provided no protection for the driver, so Doc had to wear a diving suit when he traveled through time in the time car in order to survive.
He left his family for the future in the steam time car on August 13, 1893, and had intended to arrive back seconds after he left. The time travel was a success, however due to the 19th century parts he had to use, there was a fluctuation in the space-time continuum. Doc ended up in 2035 instead of 2015, and didn't return home for days.
Marty McFly got the note, and looked for Doc in a secret lab that he was able to find, with the help of his girlfriend Jennifer. Marty and Jennifer had no idea when and where Doc had gone, so Marty wrote Doc a note and left it in the secret lab. Doc found it in 2035, while going back to the lab to pick up the clothes he wore in 2015.
However, Doc soon found himself pursued by officer Griff Tannen, after he tried to retrieve his safety deposit box from the bank. Tannen had been given a sage implant and a level one personality rewiring after he was released from prison. As he was deemed rehabilitated, he became an officer of the Hill Valley Police Department. However, the new personality implant didn't work, and Griff retained his violent tendencies. He was known to disobey orders, to use excessive force, and to use equipment that he was not authorized to use, such as a flame thrower. He also was reprimanded in the past for taking bribes.
The police were after Doc as the biological scan of Doc's age did not match that of the fake identity he set up in 2015. Doc had intended to travel back to 2015, to pick up the parts he needed, at a time that his fake identity would still be valid. However, Griff shot an electrical surge at Doc as he was about to head back in the steam time car. This surge was meant to disable his bio-mechanical implants, but since Doc didn't have any, he suffered amnesia due to the jolt.
He saw Marty's note in his pocket, and headed to the time and place that was written there, since that was his only clue as to what was happening. Doc arrived at the date on the note, March 3, 1986, in his secret lab. However, upon arriving there, he had no memory of who he was, and he was confused about the date and the location of which he had arrived. He also did not recognize Marty and Jennifer.
Marty and Jennifer decided to help the amnesiac Doc find the vehicle that had transported him there, not knowing which time machine he had used. They went to the spot where Doc had crashed into a stop sign, but the steam tricycle was gone. They discovered that the towing service, Lee Bros. Towing & Repair, had left a flyer with their company name, as they had wanted the owner of the car to know where it was towed.
They then traveled to the towing service, and discovered that a man who worked for the company, Jack, already had a buyer for the car. He stated that he would sell it to them instead for $300. Since they didn't have the money, they sneaked into the lot, and found the car still hooked up to the tow truck. Knowing that they didn't have any way to get the money, Marty decided to steal the car, tow truck and all. Douglas J. Needles arrived and threatened to smash the car, so Marty started the tow truck and sped away from Needles, who pursued him in his Ford F-150.
Marty managed to outrun Needles, who crashed into a delivery truck. Jennifer and Doc, who had split up from Marty once Needles arrived, joined back up with Marty, and they headed to the Lone Pine Mall to inspect the steam time car. They discovered that Doc had arrived in 1986 from 2035.
The time parachute
Since the steam time car would be battered by the rigors of space time, Doc surmised that it would not survive a return trip. Thus, he had come up with a plan to travel without a time machine. He devised an idea for a time parachute, in which a person would ascend in a balloon to a distance of half a mile, and then would be released from the balloon. The person would fall at a rate of 35 feet per second per second, and would reach 88 m.p.h. between four and five seconds. Since the time circuits, frictionless dynamo, and flux capacitor are connected to the parachute, the person, who would be protected from the rigors of space-time and the temperature variation by wearing a protective suit, would travel through time. The time traveler would then pull the ripcord of the parachute once they traveled through time, and arrive safely on the ground in that time period.
Since the steam time car had surprisingly survived two trips, Doc and Marty knew it wouldn't survive another trip through time. Marty grabbed a radiation suit and traveled via the time parachute with Doc to September 16, 2035. There Marty hoped that they would discover what had happened to Doc, and why he lost his memory.
The time parachute was a success, and they crashed into the glass roof of the Lone Pine Fli-Drome once they arrived in 2035. They arrived in the middle of a fliderb, a hoverboard roller derby. As they arrived in a radiation suit and a diving suit, and had crashed through the roof, the fliderb players thought they were terrorists, and called the police.
While on the run, Doc and Marty ran into officer Griff Tannen, who caught them in Bistro Twenty/15. This restaurant was themed on life in 2015, as Cafe 80's was modeled after the 1980s in 2015. Officer Tannen recognized Doc as the person who supposedly stole the identity of Leroy Brown. Once he saw the diving suit, he realized that Doc and Marty were the two people who were the cause of the disturbance at the Fliderb.
Tannen chased them in his police vehicle while they fled on hoverboards. While they were being chased, Doc fell backwards on his board and hit his head. This shock caused him to remember everything, and he told Marty all about how he had found himself in that situation once they reached Doc's secret lab.
It seemed like the two were cornered, however Marty discovered that the machine that he had turned on out of curiosity in 1986 was actually the temporal field generator mark II. Although the device could only transport objects through time during the time in which the machine had been turned on, since it was turned on nearly fifty years prior, time would not be a factor. Doc donned the diving suit and went back to 2015.
The second DeLorean time machine
Marty and Jennifer found another DeLorean DMC-12 in Doc's secret lab in 1986. Although it wasn't adapted for time travel, Marty and Jennifer took it to escape the police, who had been alerted when the alarm was tripped in the secret lab. Later, Jennifer drove it when chasing after Marty, who stole the tow truck that had the steam time car hooked up to it, and was trying to outrun Needles. At the parking lot, Jennifer ran towards the DeLorean when she spotted Needles' truck, but stopped when it turned out that Doc was driving it.
Doc had purchased a Mr Fusion in 2015, and had brought the time circuits and flux capacitor from the time parachute. He installed all of these devices into the spare DeLorean, and Jennifer and Doc headed to 2035 to rescue Marty.
When they had arrived, Commissioner Wilson had arrested Griff Tannen. She had also arrested Marty for his actions at the Fliderb, and told him that he'd likely get the same sage implant and personality rewrite that Griff Tannen had received.
Griff broke free and attempted to run them all over when Jennifer and Doc arrived in the DeLorean and knocked his hovercar out of the way. Marty got into the DeLorean and Jennifer attempted to outrun the police, who were in pursuit, along with Griff Tannen.
Doc informed Marty and Jennifer that every person in 2035 wore a suit outfitted with a hover technology protection that acted as a force field and made them bounce when hit. Knowing that the people would be unharmed, Jennifer sped full speed into a crowd of people. As the bouncing pedestrians blocked Griff's view, he did not see the sewage reclamation project ahead, and crashed into it. Jennifer sped up to 88 m.p.h and traveled back to 1986.
She informed Marty that the steam time car, minus the equipment for time travel, was in the back of Marty's truck. Marty walked Jennifer home, then Marty returned to his own home. Doc picked up Einstein, then traveled to August 14, 1893, hours after Clara dropped off the note addressed to Marty at the Western Union office.
The Jules Verne train
Later in the 1890s, Doc was able to successfully complete the Jules Verne train. He then traveled to October 27, 1985. There, the Brown family met up with Marty McFly and Jennifer Parker in the most likely place that they might be at that given time, the site of the DeLorean's destruction. He introduced his family, and explained to Jennifer how the fax that showed that Marty had been fired in 2015 disappeared after Marty chose not to drag race Douglas J. Needles in 1985. The future hadn't been written yet, so he told Jennifer and Marty to make it a good one. He also gave Marty the picture that was taken in 1885 of Marty and Doc in front of the clock that had yet to be installed in the Hill Valley Courthouse.
When the Brown family began to live part time in the 20th century, they brought the Jules Verne train with them. It had the ability for spatial displacement, which allowed it to travel to any location in any time period.
The temporal duplicate DeLorean
On May 14, 1986, a DeLorean time machine arrived at Doc's garage, six months after Doc's original DeLorean was destroyed. This DeLorean was a temporal duplicate, which had been created when the original DeLorean was hit by lightning in 1955. While the original DeLorean was sent seventy years in the past, the temporal duplicate DeLorean was sent seventy years into the future. Doc traveled to the future and discovered that DeLorean. He was able to get it back from Griff Tannen before he caused damage to the time stream.
As it was an exact duplicate of the original DeLorean, it had all the additions that the original DeLorean had when it was hit by lightning in 1955. It also had some additions that Doc had made since then, including an automatic retrieval system which would send the DeLorean to the future to retrieve Marty in the event that Doc didn't use the DeLorean for an extended period of time.
Marty played a tape of Doc explaining this feature, and realized that Doc was in trouble. He traveled to June 13, 1931 to rescue Doc. Things didn't go as planned, and Doc was erased from time due to Marty accidentally causing a young Emmett to fall in love with and marry Edna Strickland. Doc never created the time machine, so he wasn't able to get the rejuvenation treatments that extended his life.
Marty was able to convince the alternate Doc from this timeline to repair the time machine. This Doc, who went by the name Citizen Brown, traveled back to 1931 with Marty to try to fix the timeline. As they arrived at a later date then they had intended, Citizen Brown repaired the time circuits of this DeLorean, which were unstable. He used flux emitters to calibrate the time circuits to ensure that the DeLorean arrived at the right time.
When Marty proved that Edna was the arsonist who burned down the Hill Valley speakeasy, the timeline was repaired. Young Emmett never married Edna, so Citizen Brown faded from existence. Edna Strickland stole the DeLorean and accidentally headed into the past, while trying to avoid Officer Danny Parker. Marty gave young Emmett a newspaper clipping from 1986 and told him not to look at it until he was awarded the key to the city. At that point, Doc arrived in 1931, as he had received the key and then understood who had given him the newspaper clipping. This Doc had arrived in a different DeLorean, which was from the new timeline, so it didn't contain the modifications that Citizen Brown had made.
Once Hill Valley faded from existence, they realized that Edna Strickland had seriously damaged the time stream at some time in the past. Marty's great grandfather William McFly, told them about an old woman named Mary Pickford, who he thought would know about the town that used to be there.
It turns out that Mary Pickford was actually Edna Strickland, who had traveled back to 1876 and accidentally burned down the town when she tried to set fire to the Palace Saloon. After she gave them the date of the arson, Marty and Doc traveled to July 17, 1876 to stop her. Doc used flux overrides to control the flux emitters on Edna's DeLorean. They were able to remotely control her DeLorean, accelerating to 88 mph before that DeLorean faded from existence once the time bubble protecting it popped and time caught up with itself.
The new DeLorean
In 1991, Doc Brown built a new DeLorean. This DeLorean had many improvements, including audio activation of the time circuits, and spatial displacement, which, like the Jules Verne train, allowed it to travel to any place on Earth at any time period. This DeLorean also had the ability to transform into a suitcase, which prevented it from being stolen and allowed it to hidden more easily.
By 1991, Doc improved upon the temporal field capacitor with the remote control mail delivery time machine, which could send objects through time, beyond the lifespan of the device. When the Brown family were visiting the Pyramids of Giza in Egypt in 1000 BCE, a spear damaged the flux capacitor of the Jules Verne train. The time train was sent to 1692 in Salem, Massachusetts. Doc used the remote control mail delivery time machine to send a scratch and listen postcard to 1991 to let Marty know the situation.
Marty used the new DeLorean to travel back to September 23, 1692 with a spare flux capacitor. He crashed in a lake, and another addition that Doc made to the new DeLorean was revealed when an inflatable device was automatically triggered, bringing the DeLorean back to the surface. After several days, Doc was able to repair the train, and they were able to take both the Jules Verne train and the new DeLorean time machine back to 1991.
The 8-passenger DeLorean
The 8-passenger DeLorean was faster, more energy efficient, a convertible, and was equipped with a sub-ether time-tracking scanner.
It was originally planned to be used to send Doc's time travel volunteers one day into the future, but instead was used to bump Biff Tannen after he stole another DeLorean time machine, which sent both cars from the primeval Hill Valley back to 1991.
Additional time travel without a machine
Like Doc's time parachute, his son Jules devised a similar plan. After traveling from 1991 to August 5, 1926, Jules discovered his father, who was a child at the time, was going to be in a barrel going over the Upper Yosemite Falls while movie producer D.W. Tannen filmed it. To keep his father safe, Verne Brown took his place in the barrel, and Jules put a spare flux capacitor inside. As Doc had improved time travel at that point to allow for travel through both space and time, once the barrel reached 88 m.p.h., it was sent safely towards land.
Blue DeLorean time machine
On May 15th, 1986, a future version of Marty appeared in a blue DeLorean time machine. Apart from the color, this car was identical to the original DeLorean, including having the ability to fly.
Black DeLorean time machine
Shortly after the blue DeLorean arrived, another future version of Marty appeared in a black DeLorean time machine. The black DeLorean was identical to the original DeLorean, except it was black in color and had fire decals on each door. Interestingly, the wheels of this car did not appear to rotate while it was in flight, instead remaining as they would on a regular car.
Unspecified DeLorean time machines
Doc used a DeLorean time machine several times after he returned from 1885. It's unknown which time machine was used in these instances, but since they appeared similar to the original DeLorean, they were likely either the second DeLorean, the temporal duplicate DeLorean, or a new time machine.
On May 15th, 1986, a future version of Marty arrived outside Doc's garage in a DeLorean time machine.
In 1988, Doc traveled to Orlando, Florida on May 1, 1990 to visit Universal Studios Florida. He was able to have an experience beyond that of usual theme park visitors, as he was able to actively participate in the rides.
In 1991, Biff stowed away in a DeLorean time machine when the scientists from the Institute of Technology traveled to 1955. Biff stole this time machine and traveled to the future and the past, while being pursued by time travel volunteers in an 8-passenger DeLorean remotely piloted by Doc Brown.
Doc traveled to 2045 or beyond, where he witnessed the devastation caused by a nuclear holocaust which was accidentally triggered by an overload of the Mr. Fusion network by a signal sent out by Griff Tannen's ThingMeme social media application. Doc successfully traveled from 2015 to an unknown point the past to prevent the the Mr. Fusion, hover conversion, food hydrator and self-tying shoes from being available by 2015.