Construction1

This will be merged with ConstructionOrbits real soon now.

The first table describes a series of increasingly higher altitude construction orbits, with periods that are multiples of sidereal days, synchronizing the orbit with the launch loop as it rotates below.

The first "one sidereal day" orbit will be convenient for the construction of space solar power satellites in synchronous orbits. There may be as many as 96 construction station orbits, spaced around the "sidereal clock", fed by separately synchronous vehicle streams. The quickest return to Earth (say, to return a stabilized accident victim to a hospital on earth) will be from the one day orbit, with a 116 m/s retrograde delta V to drop perigee to 50 km reentry altitude in the atmosphere.

If the launch is not captured by the construction station, the vehicle will be in a shorter period orbit and not synchronize with the station on it's next pass. A 2 m/s retrograde delta V from the launch orbit will also drop perigee to 50 km reentry altitude.

The larger long period orbits will be suitable for the launch of interplanetary missions. They will suffer from larger tidal effects from the moon. Still, if the 5 day orbit at the bottom can be made to work, then the capture delta V will be a mere 40 m/s. After an interplanetary vehicle is assembled in this long period construction orbit and the interplanetary trajectory window opens, the perigee is lowered to perhaps 222 km altitude (6600 km radius) with a 37 m/s thrust at apogee. 2.5 days later at perigee, a 1.1 km/s delta V rocket burn can launch the assembled vehicle with an escape velocity excess vinf = 5.5 km/s for rendezvous with an

The referenced paper is for a spartan 75 metric tonne cycler; a vehicle built with 20 4-tonne additions every 5 days over a two year period could mass more than 10,000 tonnes, adding to a vast, shielded wheel suitable for centuries of continuous occupation.

construction orbit perigee radius = 8378 km launch orbit perigee radius = 6458 km

sid

period sec

apogee

apogee velocity m/s

perigee velocity m/s

day

constr.

launch

radius km

constr.

launch

diff.

constr.

loop

1

86164

83238

75950.3

1021.18

906.95

114.23

9257.46

10665.8

2

172328

168634

125484.9

630.56

557.63

72.94

9444.51

10834.8

3

258492

254260

167032.0

477.45

421.50

55.95

9518.89

10901.3

4

344656

339996

204116.1

392.41

346.09

46.32

9560.46

10938.4

5

430820

425798

238199.6

337.21

297.22

39.99

9587.54

10962.5

6

516985

511647

270068.0

298.02

262.56

35.46

9606.82

10979.6

7

603149

597528

300205.2

268.51

236.48

32.03

9621.36

10992.5

8

689313

683436

328935.4

245.35

216.02

29.32

9632.79

11002.6

9

775477

769364

356489.5

226.60

199.47

27.13

9642.05

11010.8

10

861641

855309

383039.5

211.06

185.76

25.30

9649.73

11017.6

Multiple vehicles per day to a one sidereal day construction orbit

Vehicles can be launched from the launch loop into higher apogee orbits over a ±15 minute window around the prime orbit; they will arrive with a bit more tangential velocity, and far more radial velocity. Vehicles launched before the prime orbit time will arrive with downward radial velocity; vehicles launched after the prime orbit time will arrive after.

I presume the vehicles will be as cheap and as close to passive and uncomplicated as possible, and will arrive near the station to be captured by an active maneuvering tether. They will be perturbed somewhat by the turbulent passage out of the thin remaining atmosphere after a high precision launch by the launch loop, and some way of thrusting them into an exactly precise (to millimeters absolute position and micrometers per second relative velocity) is needed.

When vehicles arrive, they will be "lassoed" by a velocity and position-matched loop on a deployed cable. They will pull the cable against a drum and a generator, producing electricity to drive some form of propulsion attached to the station itself. We do not need high ISP, but propellant plumes with tightly constrained velocity profiles will be designed to launch all of the propellant into a retrograde orbit with a perigee below the top of the atmosphere. An inert material like argon might be best, so it does not upset upper atmosphere chemistry too much.

Vehicles arriving at ± 900 seconds will have radial velocities around 660 m/s, or excess kinetic energies of 220 kJ/kg; if that was converted 50% efficiently to propellant kinetic energy, a 10% propellant fraction could be launched retrograde at ≈1500 m/s, an impulse of 150 kg-m/s per vehicle kg, more than enough to restore station momentum "lost" to a vehicle capture. A 670 m/s combined radial and tangential velocity capture is frightening - or perhaps "a mere engineering detail", as antimatter propulsion advocate Bob Forward was fond of saying. I don't know how to do it safely and reliably, but someone reading this may be inspired to learn how.

If the expelled propellant fraction is 10%, we can guess that perhaps one in eight of the incoming vehicles are tankers delivering liquid (argon?) propellant.

MoreLater

capture8 construction perigee = 8378 km launch perigee = 6458 km

sidereal period 1 days 86164.091 seconds

period

arrival

apogee

velocity change m/s

sec

sec

km

tangent

radial

plane

construction

86164.091

0.000

75950.339

0.00

0.00

0.00

prime cargo

83238.210

0.000

75950.339

114.23

0.00

0.00

-900s cargo

84605.521

1954.218

76850.339

114.20

-652.63

-8.32

-870s cargo

84559.824

1888.892

76820.339

114.58

-635.58

-8.04

-840s cargo

84514.136

1823.650

76790.339

114.92

-618.17

-7.76

-810s cargo

84468.456

1758.485

76760.339

115.24

-600.39

-7.47

-780s cargo

84422.784

1693.397

76730.339

115.52

-582.27

-7.19

-750s cargo

84377.120

1628.381

76700.339

115.78

-563.81

-6.91

-720s cargo

84331.465

1563.434

76670.339

116.01

-545.01

-6.63

-690s cargo

84285.818

1498.552

76640.339

116.21

-525.89

-6.35

-660s cargo

84240.179

1433.733

76610.339

116.38

-506.46

-6.08

-630s cargo

84194.548

1368.972

76580.339

116.53

-486.72

-5.80

-600s cargo

84148.925

1304.267

76550.339

116.65

-466.69

-5.52

-570s cargo

84103.311

1239.613

76520.339

116.75

-446.37

-5.24

-540s cargo

84057.705

1175.006

76490.339

116.82

-425.77

-4.96

-510s cargo

84012.108

1110.444

76460.339

116.87

-404.91

-4.69

-480s cargo

83966.518

1045.920

76430.339

116.89

-383.78

-4.41

-450s cargo

83920.937

981.432

76400.339

116.89

-362.41

-4.13

-420s cargo

83875.364

916.973

76370.339

116.87

-340.80

-3.86

-390s cargo

83829.799

852.539

76340.339

116.82

-318.96

-3.58

-360s cargo

83784.243

788.123

76310.339

116.76

-296.90

-3.31

-330s cargo

83738.695

723.717

76280.339

116.67

-274.62

-3.03

-300s cargo

83693.155

659.313

76250.339

116.55

-252.13

-2.76

-270s cargo

83647.623

594.901

76220.339

116.42

-229.43

-2.48

-240s cargo

83602.099

530.467

76190.339

116.26

-206.53

-2.20

-210s cargo

83556.584

465.991

76160.339

116.09

-183.41

-1.93

-180s cargo

83511.077

401.450

76130.339

115.89

-160.06

-1.65

-150s cargo

83465.579

336.806

76100.339

115.67

-136.45

-1.38

-120s cargo

83420.088

271.998

76070.339

115.43

-112.53

-1.10

-90s cargo

83374.606

206.920

76040.339

115.16

-88.17

-0.83

-60s cargo

83329.132

141.354

76010.339

114.88

-63.12

-0.55

-30s cargo

83283.667

74.699

75980.339

114.57

-36.64

-0.28

prime cargo

83238.210

0.000

75950.339

114.23

0.00

0.00

30s cargo

83320.865

38.227

76004.884

114.85

42.83

0.28

60s cargo

83391.496

58.300

76051.481

115.35

70.36

0.55

90s cargo

83460.787

76.359

76097.180

115.82

96.13

0.83

120s cargo

83529.441

93.472

76142.446

116.25

121.03

1.10

150s cargo

83597.718

110.036

76187.451

116.67

145.38

1.38

180s cargo

83665.745

126.248

76232.280

117.05

169.32

1.65

210s cargo

83733.595

142.218

76276.980

117.42

192.94

1.93

240s cargo

83801.311

158.017

76321.580

117.76

216.28

2.20

270s cargo

83868.922

173.693

76366.098

118.08

239.37

2.48

300s cargo

83936.447

189.278

76410.548

118.38

262.21

2.75

330s cargo

84003.901

204.798

76454.939

118.65

284.81

3.02

360s cargo

84071.292

220.271

76499.278

118.91

307.17

3.30

390s cargo

84138.630

235.712

76543.568

119.14

329.30

3.57

420s cargo

84205.918

251.132

76587.815

119.35

351.18

3.85

450s cargo

84273.161

266.542

76632.020

119.53

372.81

4.12

480s cargo

84340.361

281.950

76676.185

119.69

394.19

4.40

510s cargo

84407.520

297.362

76720.312

119.83

415.30

4.67

540s cargo

84474.641

312.786

76764.401

119.95

436.14

4.95

570s cargo

84541.722

328.226

76808.454

120.04

456.71

5.22

600s cargo

84608.766

343.687

76852.469

120.11

476.98

5.50

630s cargo

84675.771

359.174

76896.449

120.15

496.96

5.78

660s cargo

84742.738

374.691

76940.391

120.17

516.63

6.05

690s cargo

84809.667

390.241

76984.296

120.16

535.98

6.33

720s cargo

84876.555

405.828

77028.164

120.12

555.01

6.61

750s cargo

84943.403

421.455

77071.993

120.06

573.71

6.88

780s cargo

85010.210

437.125

77115.784

119.97

592.08

7.16

810s cargo

85076.973

452.842

77159.535

119.85

610.09

7.44

840s cargo

85143.693

468.608

77203.246

119.71

627.75

7.72

870s cargo

85210.366

484.425

77246.915

119.53

645.04

8.00

900s cargo

85276.992

500.297

77290.542

119.33

661.97

8.28

Construction1 (last edited 2018-12-06 23:03:38 by KeithLofstrom)