This crude graphic I made by hand in 2023.
This graphic I made 17-Apri-2026 22:21 PDT using Claude.
Jupiter slowly moved into position so that if an object entered an elliptical orbit with perihelion at 800,000,000 kilometers and an aphelion of 150,000,000 kilometers, then the earth would be at the aphelion, same place at the same time. The flight plan was to leave orbit over Europa and transfer to a hyperbolic orbit around Jupiter. The far end of the hyperbola would be a trajectory towards Earth, a Hohmann transfer orbit. However, nature always balances her books, and the change in momentum to the timeship would be exactly the opposite to the change in momentum in Jupiter. Of course, since Jupiter is incredibly massive compared to the timeship, the change in its motion would be infinitesimal. They picked a departure time in the middle of the launch window. They were concerned about running out of reaction mass when they arrived at Earth, so the plan was to conserve reaction mass at launch.
The burn to leave orbit over Europa was carried out with impeccable precision. They began falling towards Jupiter. The radiation recorders on the outside of the timeship’s hull recorded very high levels of radiation, but inside the ship, between the iron shot in the shell and the water in the reaction mass tanks, the radiation levels were insignificant. Adelle monitored their position at all times using astronomical observations of the Jovian moons and the stars, and inputs from the inertial navigation system. This information was summarized and displayed for Walter and Deborah. Their target window was an ellipse 50 kilometers high by 30 kilometers wide. Adelle reported that their position was within 1 kilometer of nominal and that their velocity vector was 1.2 centimeters/second from nominal. However, it was a tense time, and they got little sleep. Achiya also needed attention, and that cut into Deborah’s sleep time even more. Their exercise routine suffered, and all three of them gained weight.
Adelle was the first one to notice. “Our velocity vector error has increased to 1.1 meter/second and the direction has changed”
“Display the error on the NAV screen”
The navigation display immediately showed the error, in 3D using an anaglyph, Deborah and Walter put on glasses with a red filter over the left eye and a green filter over the right eye.
“I think I know what’s wrong - there’s too much drag from the Jovian atmosphere”, Deborah said.
“Can we compensate?”, Walter asked.
“That’s not my chief concern. The timeship is too fragile to fly through an atmosphere. I’m worried that the ship may fall apart due to aerodynamic stresses, or that the skin could melt from overheating. Adelle, what is the temperature of the outer hull?”
“-65 ℃”
“Estimated drag?”
“1 times ten to the eleventh Newtons and rising” Estimate mass of timeship. 1.4E+13 Kg
“Doesn’t the timeship weigh something like 10 to the thirteenth kilograms?”, Walter asked.
“Actually, about a quarter of our reaction mass is gone, so that’s about right”, Deborah answered. “Adelle?”
“Yes”
“How much time to closest approach to Jupiter?”
“Two minutes, 41 seconds”
“So, there are two options: 1) is that we do a course correction now. That will make us go even faster through the atmosphere and cause more drag. Aerodynamic drag of a supersonic object increases linearly. 2) We can wait until after we clear the atmosphere. Then we will have a better idea of the effect of the drag integrated over time.”
“There is a third option: we could make a course correction side ways to get us out of the atmosphere right away and then do another course correction to make up for all the problems we’re having. I worry that the aerodynamic forces may cause metal fatigue and cause the timeship to disintegrate”, Walter said. I notice the Walter is perspiring. We should have given him some physics training.
“Adelle?”
“Yes”
“Is it feasible to get us out of the atmosphere right away and then do another course correction once we get out of the atmosphere? What is the temperature of the hull now? How much time to closest approach to Jupiter”
“It is feasible to get out of the atmosphere now and then correct the course later on. The hull temperature is now -11 ℃. There is now two minutes 11 seconds to closest approach”
“Adelle: get us out of the atmosphere now”
“Understood”
The NAV display showed the timeship pitching at right angle to its course. The error vector changed direction, but not magnitude, as the timeship started moving sideways.
“We have left the atmosphere. Preparing a course correction to reduce the error velocity vector to zero”, Adelle announced.
The timeship rolled and pitched. The velocity error vector began reducing magnitude. Eventually, it disappeared.
“We’re on course for Earth. Estimated arrival time one thousand three hundred twenty two days”, Adelle announced.
“I’m going to check on Achiya”, Deborah told Walter.
“I’m going to take a nap”, Walter said.
Achiya was fast asleep in his bassinet. The artificial gravity had worked well: he had not stirred during his near-death experience.
Interplanetary travel is probably one of the most boring activities ever imagined. The view never changes, there are no waves, no clouds, there is no weather, no seasons, not even night and day. Even in the middle of the asteroid belt, space is, well, empty space. Adelle used an omni directional pulsed doppler radar just to make sure that there was nothing within a 100,000 kilometers of them. So, aside from the usual dangers of traveling in space, there was no particular danger. When something broke, Adelle usually fixed it automatically. The massive matter-anti-matter power plants were in idle. Walter was off playing video games, although he and the replicator were making wonderful meals together. Achiya was the only thing interesting, however, poopy diapers lost their interest after a while. Deborah continued to exercise with Walter, only now she attached 10 kilogram weights to her ankles in hopes of compensating for the 1 G environment in the village. Nursing Achiya was one of the highlights of her day: lactating released Oxytocin, which worked on the pleasure center of her brain. Then Achiya began eating solid food. This was a problem: Deborah didn’t know what small children ate a thousand years before the common era. She realized that Achiya was going to face a life of relatively bland culinary arts. Achiya picked up words at an astonishing pace. Perhaps the reason why was that when Deborah and Walter talked around Achiya, they spoke in Hebrew, and ancient Hebrew has a much simpler vocabulary than modern Hebrew, and much much simpler than English.
Four years passed in this quiet monotony. Deborah was an attentive parent, and the autodoc was full of helpful advice. In her copious spare time, Deborah wrote a commentary on the Book of Daniel in both Hebrew and English. Achiya grew rapidly, thanks to 24th century medical care. Walter liked rough housing with Achiya. On his fourth birthday, Walter presented him with an authentic wooden sword and a leather scabbard. They practiced martial arts together. In 1/6th gravity, Achiya could jump several meters into the air, pivot, and deliver a kick with muscles toned in a 1 G environment. After a few episodes of this type, Walter started wearing a jock strap for this activity.
Deborah’s martial arts training had also progressed. She should break a concrete cinder block with her bare hands, and break a 2 centimeter thick piece of hardwood with her bare foot. She practiced sword fighting against an avatar. Walter programmed the avatar with faster reflexes, and challenged Deborah to keep up. She also practiced with the laser pistol and rifle. She was becoming a dangerous woman indeed.