Earth To Orbit

A table of launch information.

Destination

Launch V

2000km

2000km

10 gee

10 gee

transit

Arrival

altitude

radius

V m/s

gees

time s

dist km

time s

hrs

∆V m/s

km

km

LEO

7451

1.41

537

283

76

0.74

65

300

6678

m288

8586

1.88

466

376

88

1.30

1009

6411

12789

GEO

9875

2.49

405

497

101

5.24

1490

35786

42164

Moon

10547

2.84

379

567

108

119.42

833

378022

384400

Slingshot Moon to m288

10547

2.84

379

567

108

241.74

-2184

6411

12789

Slingshot Moon to GEO

10547

2.84

379

567

108

255.56

-1053

35786

42164

Note that the slingshot orbits show negative arrival ∆V. With some kind of rotating or linear tether system at the arrival orbit, the positive ∆V from ground launch payloads and the negative ∆V from a slingshot payloads can be averaged. This greatly reduces the size of the orbital insertion kick motors needed to inject payloads into these orbits. By sending 30% of m288 payloads the long way around the moon, for example, the cost of delivering payloads to m288 could be halved.

Rotating Tether orbits

Apogee can be circularized without big rocket motors by using rotating tethers. Assume 3 gees centifugal force on the tether ends, 5 ton payloads (150kN), with some sort of magic that briefly reduces the attach shock. The tether rotates with end speeds of 0.5*∆V, and is that much slower than the circular orbit it injects into. The mass is that needed for the tether, using Kevlar with a design support length of 60km-gee or a characteristic velocity of 770m/s, or a "space elevator strength" of 0.6 MegaYuri. Taper is not needed for any of the destination orbits, and in fact some extra end mass may be added to increase stored angular momentum.

Payload

Tether Orbit

Tether Properties

Destination

Circular

Delta V

Perigee

Perigee

Apogee

Apogee

Length

Period

Mass

notes

m/s

m/s

V m/s

R km

V m/s

R km

km

sec

kg

LEO

7726

65

7825

6566

7693

6678

0.07

3.4

18

orbit too crowded for tether

m288

5583

1009

7206

9006

5078

12780

17.97

52.8

4546

GEO

3075

1490

5788

16966

2330

42146

37.00

78.0

9361

may need taper

Moon

1018

833

2662

90975

603

384394

11.56

43.6

2924

There will probably be a fairly large counterweight in the middle. Alternately, the tether will be much more massive than needed for supporting one payload. This means its orbit shifts less when capturing one payload. The restoring velocity may come from returning payloads, or from loop-launched mass passing tangentially by the rotating tether in a fast orbit from above or below, possibly with lunar slingshot assist. Mad handwaving here.

The initial tether will probably be injected from a slingshot orbit around the moon, and deployed vertically. Additional launches directly from the loop on the ground will add mass and lower the perigee. There may be some rocket thrust required initially to get the first tether set up, but after that, mass can be added with properly timed loop-launched payloads. More mad handwaving!

EarthToOrbit (last edited 2009-08-24 05:12:42 by KeithLofstrom)