Now here is a philosophical answer to how you can practice scales without a trumpet... Use a keyboard. I find visualizing key positions very helpful in how I translate scales to the trumpet. Example: Whole note scales: I visualize the white and dark keys separated by 2 and 3 black noted patterns. If I start on white in the 2 black note part of the keyboard (C) the next note will be white (D) as will the next (E), but now I enter the three black note part of the scale, and visually switch to the black keys (F#, G#, A#) then I exit the 3 black not pattern and re-enter the 2 black note pattern, where I convert back to white notes: (C). Whole note scale is practiced (in my mind) and converted to the horn (by my fingers) as: C, D, E, F#, G#, A#, C, D then back down. Hope I did not hurt any body with this visual conversion. I am very right brained and find the keyboard helps me with nearly all of my scales and improvisation around chords.