For those wondering what characters you need for DSH. a few get unlocked at each stage but the final 100 stars needed for shuttle the following can be used:
Deep Space Homer-Train an Astronaut, 3hrs Earns 1 star
Deep Space Homer- Collect Insect Specimens, 8hrs Earns 2 star
Quimby- Work Out Payments, 3hrs, Earns 1 star
Marge- Do Narobics, 3hrs, Earns 1 star
Marge- Put Rocket Ship Together, 3hrs, Earns 1 star
Bart- Put Rocket Ship Together, 3hrs, Earns 1 star
Grampa- Put Rocket Ship Together, 3hrs, Earns 1 star
Miss. Hoover- Do Narobics, 3hrs, Earns 1 star
Luann- Do Narobics, 3hrs, Earns 2 star
Astronaut Barney- Demonstrate Balance, 3hrs, Earns 2 star
Snake- Collect Payments, 3hrs, Earns 1 star
Don Vittorio- Collect Payments, 3hrs, Earns 2 star
Fat Tony- Collect Payments, 3hrs, Earns 1 star
Legs- Collect Payments, 3hrs, Earns 1 star
Louie- Collect Payments, 3hrs, Earns 1 star
Milhouse- Hang Out at the Hanger, 3hrs, Earns 1 star
Martin- Hang Out at the Hanger, 3hrs, Earns 1 star
Database- Hang Out at the Hanger, 3hrs, Earns 1 star
Lisa- Teach Astrophysics, 3hrs, Earns 1 star
Lisa- Put Rocket Ship Together, 3hrs, Earns 1 star
NARA Training Center- Earns 5 star/3hrs
Shuttle Simulator- Earns 5 star/3hrs