When Asumi was just a baby, a space shuttle accident changed her life, and the lives of the townspeople of Yuigahama, forever. As a young woman, the spirited Asumi has only one desire: to someday travel to the stars in a rocket, with her father and ghostly friend Lion-san along for the ride. With heartache, happiness, and plenty of determination, Asumi and dozens of talented teenagers now face the greatest challenge of their lives: the test to enter a prestigious space academy, so that they may one day reach out and touch the stars...
In search of answers, Yukari Morita travels to the place where her father had abandoned her mother seventeen years ago on their honeymoon night. When she reaches the Solomon Islands, an unlikely sequence of events occurs and her fate becomes intertwined with that of Solomon Space Agency. She meets Isao Nasuda, the director of SSA, who happens who be quite the opportunist. Nasuda is willing to help her find her father, but at a price: doing a simple job, pressing buttons -- something even a monkey could do! Little does she know she'll be piloting Japan's first manned rocket into outer space!
While Twin Spica focuses more on calm emotions and Rocket Girls is more abrasive and at times, ecchi, both series involve young people who must learn to travel to space, with plenty of tests and such along the way.
When Mutta and Hibito were children, they made a promise to become astronauts together after spotting a UFO one night. Now adults, the duo's path couldn't have diverged more – Hibito is about to travel to the moon with NASA to help simulate the future exploration of Mars, and Mutta is unemployed, having recently headbutted his boss at an auto company. Still, the man can't shake his desire to surpass his younger brother, and soon, he becomes an applicant for Japan's JAXA space program. His ultimate goal, to get one step ahead of Hibito and go to Mars. But the path to becoming an astronaut is long and fraught with tests and challenges. Will Mutta and newfound friends Kenji and Serika manage to persevere and achieve their dream?
Twin Spica and Space Brothers follow a group of would-be astronauts as they train to go to space. Beyond that, there's not a huge amount in common - SB is somewhat comedic, TS has a younger feel. The Twin Spica manga (which is MUCH better than the anime) is a better rec than the anime, but the anime works too. If you liked watching astronauts train in one, try the other.
In the year 2058, mankind is about to take its first leap into the distant reaches of space. Using the resources at the tail end of a comet, massive spaceships will be sent to the corners of the universe in an attempt to colonize other worlds, but due to the length of time it will take to arrive at even the closest solar system, the comets must be destroyed in-flight, resulting in super-fast speeds that will kill any life onboard; only frozen sperm and eggs, and machines will survive the journey. Carrying the unborn children of the Robinsons, the first of these ships must now set forth to Ozma; and with its precious cargo is coupled the hopes and fears of all humanity.
If you enjoyed watching Asumi daydream of visiting the stars, you'd surely enjoy the epic journey of a number of children to a distant corner of space. You won't find the similar character development or lighthearted moments, but I don't see why you wouldn't enjoy it.
Tada is a young man on the fast track to the Cosmo Academy -- a school which only accepts applicants every three years, and whose entrance rate is under 1%. Having passed all the prior exams, the final test is drawing near: survive for 53 days aboard a derelict spaceship with only 9 other would-be cadets to assist you. But much to the dismay of Tada and his peers, their ship has acquired an eleventh member! Can the crew band together to survive the test? Or will sabotage simply destroy them from within...
Kazuhiro Uchida has always dreamed of becoming a fighter pilot, but has been forced into the helicopter-training program instead. Embittered and discouraged, he still completes the training and is given his first position in a helicopter rescue unit. The catch? It’s located in a new town, far away from his loved ones. But the job of a rescue worker is incredibly demanding, both mentally and physically, and Kazuhiro’s less than enthusiastic attitude just won’t cut it. In order to succeed in his new career, Kazuhiro must survive the harsh reality of rescue work, and rediscover his dream.
Twin Spica is the story of Asumi's personal growth, with an undertone of the individual striving against the impersonal forces of nature.
Similarly, although Rescue Wings is more or less one long advertisement for the excellence and faithfulness of the JSDF, it also contains the elements of a personal growth story in the face of nature's forces, as Kazuhiro meets the challenges of the crises that his rescue unit is presented with.
If you like one of these anime, give the other a chance.