Went on this trip as I had a free day in Houston, was interested to go and visit NASA and as part of the tour they give you a tour around the city for an hour first.
Very informative for the city tour, and then you are shuttles to nasa where you receive a ticket and have 4 hours on your own tile to look around, my suggestion is do the tram tour first as it’s an hour and half, and you may need to wait to get on the tram tour.
All in all, good value for money, nice staff, and a good day spent learning about Houston and seeing NASA.