04 · The bill
Losses
Circular LEO is 7.8 km/s. Gravity while you burn, air, steering — then a 465 m/s coupon if you go east from the equator. The budget is 9.4.
In English
Orbital speed is 7.8 km/s. You still fight gravity during a long burn, punch air, and steer. Earth spinning east is a few hundred metres per second back. The real ticket is about 9.4.
- Try this
- Drag T/W from 1.1 to 2. Gravity loss should fall. Read the bill.
- Keep this
- The budget is 9.4, not 7.8. High T/W spends less time hanging.
Lab · the bill is not 7.8
Circular LEO is 7.8 km/s. You still have to fight gravity while you burn, punch air, and steer. Earth spinning east is a coupon, not a gift large enough to skip the rest.
Liftoff T/W = 1.40
- Orbital speed+7.80 km/s
- Gravity loss+1.50 km/s
- Drag+0.15 km/s
- Steering+0.25 km/s
- Earth rotation (equator)−0.47 km/s
Budget 9.23 km/s · in the usual 9.3–9.5 band
Gravity loss is roughly the integral of g·sin(pitch) during the burn. High T/W shortens the integral. Gravity turn pitches early so you are not fighting at 90° for long.
The 465 m/s equatorial coupon is v = ω R cos(latitude). It is real and it is not most of the ticket. Polar launches forfeit it.