32 motors come built in:

                                           dia  length    loaded       total   average    burn
designation  maker     type        class    mm      mm    mass g impulse N·s  thrust N  time s
B4           Quest     single-use  B        18      80      19.8         4.9       4.4    1.11
C5           Estes     single-use  C        18      70      23.8         7.8       3.9    1.98
D5           Quest     single-use  D        20      96      45.1        17.6       3.8    4.59
E26W         AeroTech  single-use  E        24      88      44.0        27.6      23.5    1.18
26E31-15A    Cesaroni  reload      E        24      69      52.0        26.1      30.7    0.85
F52C         AeroTech  single-use  F        29     111      81.4        66.3      52.8    1.25
68F240-15A   Cesaroni  reload      F        24     133      91.8        68.0     236.6    0.29
F15          Estes     single-use  F        29     114     103.0        49.6      14.5    3.42
G69N         AeroTech  reload      G        38     106     201.0       136.3      72.1    1.89
131G84-10A   Cesaroni  reload      G        24     228     172.0       131.3      84.2    1.56
H170M        AeroTech  reload      H        38     191     330.0       318.0     165.4    1.92
168H54-10A   Cesaroni  reload      H        29     187     209.0       168.2      53.8    3.13
H125-CT      Loki      reload      H        38   177.8     342.0       241.7     125.0    1.93
I175WS       AeroTech  single-use  I        38     214     348.0       333.2     177.5    1.88
411I175-14A  Cesaroni  reload      I        38     245     437.5       411.4     174.1    2.36
I377-CT      Loki      reload      I        38     292     560.0       525.8     377.9    1.39
J450DM       AeroTech  single-use  J        54     359    1223.0      1061.6     465.6    2.28
1266J760-19A Cesaroni  reload      J        54     329    1076.8      1267.3     758.2    1.67
J300LR       Loki      reload      J        54     327    1315.0      1212.8     297.0    4.08
K400C        AeroTech  single-use  K        54     359    1194.0      1307.3     409.8    3.19
2245K1075-P  AMW       reload      K        54     728    2638.8      2255.1    1072.9    2.10
1633K940-18A Cesaroni  reload      K        54     404    1366.5      1636.1     936.9    1.75
L2500ST      AeroTech  reload      L        98     443    4989.5      4671.9    2501.7    1.87
3300L3200-P  Cesaroni  reload      L        75     486    3263.7      3299.6    3206.8    1.03
L1040LR      Loki      reload      L        54     736    2962.0      3722.5    1037.1    3.59
M1350W       AeroTech  single-use  M        75     622    4808.0      5179.5    1350.1    3.84
8187M1545-P  Cesaroni  reload      M        75    1025    7878.3      8181.8    1547.7    5.29
M1378LR      Loki      reload      M        54    1108    4331.0      5362.3    1375.6    3.90
N3300R       AeroTech  reload      N        98    1060   12269.0     14035.1    3189.9    4.40
13628N5600-P Cesaroni  reload      N        98    1010   11280.0     13633.5    5626.1    2.42
O6000W       AeroTech  single-use  O       152    1120   31524.6     39687.2    5828.8    6.81
21062O3400-P Cesaroni  reload      O        98    1239   16842.0     21041.0    3424.3    6.14

From the .eng file: I377CT by Loki, 38 mm by 292 mm, 560 g loaded, 250 g of propellant
  525.8 N·s (class I), 377.9 N average over 1.39 s, 657.0 N peak
  effective exhaust velocity 2103 m/s

Valetudo on the I377CT: 8.82 kg at liftoff
  leaves the 3 m rail at 17.7 m/s
  apogee 151.7 m above the pad, at 6.09 s
Not yet validated: see the Accuracy page before trusting these numbers.
