Differences between revisions 9 and 50 (spanning 41 versions)

Propellant Plume Gas Scattering

H density versus altitude

alt km	radius km	#/m3
1000	7378	21000e6
2000	8378	12000e6	Constr. perigee
5000	11378	3100e6
10000	16378	820e6
20000	26378	180e6
30000	36378	67e6
35786	42164	45e6	GEO circular
40000	46378	35e6
50000	56378	22e6
60000	66378	14e6
69572	75950	11e6	Constr. apogee
70000	76378	10e6
image source

. https://www.sciencedirect.com/science/article/pii/0022407372900052

Estimated hydrogen mass per 1000 km height, 1.67e-27kg/H
Altitude km	1000	2000	10000	20000	30000	35786*	40000	50000	60000	69572*	70000
Radius km	7378	11378	16378	26378	36378	42164*	46378	56378	66378	75950*	76378
Volume km³	6.8e11	1.6e12	3.4e12	8.7e12	1.7e13	2.2e13	2.7e13	4.0e13	5.5e13	7.2e13	7.3e13
#H / m³	2.1e10	1.2e10	8.2e8	1.8e8	6.7e7	4.5e7	3.5e7	2.2e7	1.4e7	1.1e7	1.0e7
H kg	240000	32000	4700	2600	1900	1700*	1000	1500	1300	1300*	1200

Less than 20 tonnes of hydrogen (and almost nothing else) above GEO, out to the bow shock.

Collision cross section table

Gas	(nm)²	(nm)² with H₂
H₂	0.27	1.02
He	0.21	0.99
Ar	0.36	1.06
O₂	0.40	1.07
N₂	0.43	1.08
CH₄	0.46	1.09
CO₂	0.52	1.11
Cl₂	0.93	1.22

The second column is the combined collision cross section with an H₂ molecule ... the square of the sum of the square roots.

from libretexts

http://hitran.org . . . . . . . . . k*l at k*l dot com on kao3

24 hour "Construction" Orbit

Note: 75950 km radius is the apogee of a "24 hour" geosynchronous (but NOT geostationary) orbit with a 8378 km radius (2000 km equatorial altitude) perigee. The same 42164 km semimajor axis as a circular geostationary orbit. This is a High Eccentricity Earth Orbit (HEEO), suggested by space scientist John Lewis at the University of Arizona. Given the high perigee velocity of a launch loop, this orbit is easier to achieve with much less apogee insertion ΔV than a GEO orbit. The perigee velocity of this HEEO orbit is high, and that is an excellent place for a high ΔV thrust into an interplanetary trajectory.

Subnote 1: due to the J₂ nonlinearity of the Earth's gravity field, this orbit will precess, so an exact synchronous orbit will have a slightly smaller semimajor axis.

Subnote 2: launchloop launches slows portions of the rotor; restoring rotor position and velocity requires enormous power. Larger vehicles would slow the rotor more, requiring more peak electrical power generation capacity. It is cheaper to assemble large interplanetary vehicles at a permanent orbiting construction station from dozens, perhaps hundreds of daily launches, then launch the propellant to fuel them after they are assembled.

Since a launch to an interplanetary Hohmann must occur at a specific sun-relative angle for a particular mission, the perigee angle of the construction orbit for a Mars mission at one Hohmann opportunity will differ from the next opportunity. This is an annoying constraint for infrequent Mars missions, but less so for missions to many different asteroids.

-  ⇤ ← Revision 9 as of 2019-03-31 02:56:49 → 
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  Comment:
+   ← Revision 50 as of 2020-08-28 05:24:41 → ⇥
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  Editor: KeithLofstrom
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-Deletions are marked like this.
+Additions are marked like this.
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- . http://hitran.org keithl@keithl.com on kao3
 
 . https://www.sciencedirect.com/science/article/pii/0022407372900052
+-------
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+Line 5:
-H density versus altitude:
+=== H density versus altitude ===
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+Line 7:
-||<|9> {{ attachment:geocoronaMarkup.png | | width=600 }} || alt || #/m3 ||
||  2000 km || 10e9 ||
|| 10000 km ||  1e6 ||
|| 20000 km ||  1e6 ||
|| 30000 km ||  1e6 ||
|| 40000 km ||  1e6 ||
|| 50000 km ||  1e6 ||
|| 60000 km ||  1e6 ||
|| 70000 km ||  1e6 ||
+||<|16> {{ attachment:geocoronaMarkup.png | | width=600 }} ||<)> '''alt km''' ||<)> '''radius km''' ||<)> '''#/m3''' ||
||<)>  1000 ||<)>  7378 ||<)> 21000e6 ||
||<)>  2000 ||<)>  8378 ||<)> 12000e6 || Constr. perigee ||
||<)>  5000 ||<)> 11378 ||<)>  3100e6 ||
||<)> 10000 ||<)> 16378 ||<)>   820e6 ||
||<)> 20000 ||<)> 26378 ||<)>   180e6 ||
||<)> 30000 ||<)> 36378 ||<)>    67e6 ||
||<)> 35786 ||<)> 42164 ||<)>    45e6 || GEO circular    ||
||<)> 40000 ||<)> 46378 ||<)>    35e6 ||
||<)> 50000 ||<)> 56378 ||<)>    22e6 ||
||<)> 60000 ||<)> 66378 ||<)>    14e6 ||
||<)> 69572 ||<)> 75950 ||<)>    11e6 || Constr. apogee ||
||<)> 70000 ||<)> 76378 ||<)>    10e6 ||
||<-3> [[attachment:geocoronaMarkup.png | image source ]] ||

. https://www.sciencedirect.com/science/article/pii/0022407372900052
-Line 20:
+Line 25:
-from [[ https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/Modeling_Reaction_Kinetics/Collision_Theory/Collisional_Cross_Section | libretexts ]]:
+||<-12> Estimated hydrogen mass per 1000 km height, 1.67e-27kg/H  ||
|| Altitude km || 1000   || 2000   || 10000  || 20000  || 30000  || 35786* || 40000  || 50000  || 60000  || 69572* || 70000  ||
|| Radius km   || 7378   || 11378  || 16378  || 26378  || 36378  || 42164* || 46378  || 56378  || 66378  || 75950* || 76378  ||
|| Volume km³  || 6.8e11 || 1.6e12 || 3.4e12 || 8.7e12 || 1.7e13 || 2.2e13 || 2.7e13 || 4.0e13 || 5.5e13 || 7.2e13 || 7.3e13 ||
|| #H /  m³    || 2.1e10 || 1.2e10 || 8.2e8  || 1.8e8  || 6.7e7  || 4.5e7  || 3.5e7  || 2.2e7  || 1.4e7  || 1.1e7  || 1.0e7  ||
|| H kg        || 240000 ||  32000 ||  4700  ||  2600  || 1900   || 1700*  || 1000   || 1500   || 1300   || 1300*  || 1200   ||
-Line 22:
+Line 32:
-||<-3> Cross section         ||
|| Gas  || (nm)² || (nm)² H₂ ||
+Less than 20 tonnes of hydrogen (and almost nothing else) above GEO, out to the bow shock.

===  Collision cross section table ===

|| Gas  || (nm)² || (nm)² with H₂ ||
-Line 32:
+Line 45:
+The second column is the combined collision cross section with an H₂ molecule ... the square of the sum of the square roots.

from [[ https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/Modeling_Reaction_Kinetics/Collision_Theory/Collisional_Cross_Section | libretexts ]]

-----

 . http://hitran.org . . . . . . . . . k*l at k*l dot com on kao3

-----

=== 24 hour "Construction" Orbit ===
'''Note:''' 75950 km radius is the apogee of a "24 hour" geosynchronous (but NOT geostationary) orbit with a 8378 km radius (2000 km equatorial altitude) perigee.  The same 42164 km semimajor axis as a circular geostationary orbit.  This is a High Eccentricity Earth Orbit (HEEO), suggested by space scientist John Lewis at the University of Arizona.  Given the high perigee velocity of a launch loop, this orbit is easier to achieve with much less apogee insertion ΔV than a GEO orbit.  The perigee velocity of this HEEO orbit is high, and that is an excellent place for a high ΔV thrust into an interplanetary trajectory. 

'''Subnote 1:''' due to the J₂ nonlinearity of the Earth's gravity field, this orbit will precess, so an exact synchronous orbit will have a slightly smaller semimajor axis.

'''Subnote 2:''' launchloop launches slows portions of the rotor; restoring rotor position and velocity requires enormous power.  Larger vehicles would slow the rotor more, requiring more peak electrical power generation capacity.   It is cheaper to assemble large interplanetary vehicles at a permanent orbiting construction station from dozens, perhaps hundreds of daily launches, then launch the propellant to fuel them after they are assembled.  

Since a launch to an interplanetary Hohmann must occur at a specific sun-relative angle for a particular mission, the perigee angle of the construction orbit for a Mars mission at one Hohmann opportunity will differ from the next opportunity.  This is an annoying constraint for infrequent Mars missions, but less so for missions to many different asteroids.

Diff for "GasScatter"

Propellant Plume Gas Scattering

H density versus altitude

Collision cross section table

24 hour "Construction" Orbit