Differences between revisions 11 and 12

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

Aldrin Mars cycler orbit.

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.

My guess is that a reusable "thrust panel" consisting of a "black" laser-absorbent refractory metal sponge, saturated (somehow) with lots of hydrogen, can be designed to eject that hydrogen at very high velocity when it is smacked by a laser pulse from an orbiting station with very big optics. Wild handwaving, but a laser propulsion genius like Leik Myrabo or Jordin Kare might have some good ideas about how to do it (is Jordin's collaborator Tom Nugent still active?). Depleted panels will be returned to Earth for recharge and resuse, or used for bulk shielding.
An ablative rubber panel might also work, but might scatter too much material into persistent retrograde orbits and pollute low-Earth orbital space with ram-surface-eroding material. A '''No Gram Left Behind''' policy will be necessary for a permanent gigatonne/year spacefaring civilization.

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

-  ⇤ ← Revision 11 as of 2018-12-04 23:58:32 → 
  Size: 12571
  Editor: KeithLofstrom
  Comment:
+   ← Revision 12 as of 2018-12-06 23:03:38 → ⇥
  Size: 12620
  Editor: KeithLofstrom
  Comment:
-Deletions are marked like this.
+Additions are marked like this.
 Line 18:
-will suffer from larger tidal effects from the moon.  Still, if the 10 day orbit at the bottom
can be made to work, then the capture delta V will be a mere 25.3 m/s.  After an interplanetary
+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
 Line 21:
-window opens, the perigee is lowered to perhaps 222 km altitude (6600 km radius) with a 24 m/s
burn at apogee, then the main interplanetary launch delta V rocket burn ( v__inf__ = 5.5 km/s ) 
of 1.4 km/s will put the assembled vehicle into a [[ attachment:2006Low-ThrustAldrinCyclerwithReducedEncounterVelocities.pdf | Aldrin Mars cycler orbit ]].  The referenced paper is for a spartan 75 metric tonne cycler;  a vehicle
constructed with five or six 5-tonne additions per day over a one year period could mass 10,000 
tonnes; a vast, shielded wheel habitat suitable for multi-generation occupation.
+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 v__inf__ = 5.5 km/s for  rendezvous with an
 [[ attachment:2006Low-ThrustAldrinCyclerwithReducedEncounterVelocities.pdf | Aldrin Mars cycler orbit ]].  
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.

Diff for "Construction1"

Construction1

Multiple vehicles per day to a one sidereal day construction orbit