Re: Ephemerides for Falcon Heavy hardware?

From: Marco Langbroek via Seesat-l <seesat-l_at_satobs.org>
Date: Tue, 6 Feb 2018 13:36:45 +0100
Op 6-2-2018 om 06:02 schreef Mike McCants via Seesat-l:
> There is a press kit at:
> 
> http://www.spacex.com/sites/spacex/files/falconheavypresskit_v1.pdf
> 
> This gives a timeline which includes:
> 
> 00:03:15 2nd stage engine starts
> 00:08:31 2nd stage engine cutoff (SECO-1)
> 
> and
> 
> 00:28:22 2nd stage engine restarts
> 00:28:52 2nd stage engine cutoff (SECO-2)
> 
> I would guess that the 5 minute burn will simply get the payload
> into low Earth orbit.
> 
> Then the 30 second burn will circularlize that orbit.
> 
> The orbit could be anything between 200 to 400 miles.


Elon Musk has stated that the 6-hour coasting is to demonstrate the ability of
the Falcon Heavy to directly insert into GEO. Note that Musk has also said
something about a risk posed by 6 hour long coasting in the Van Allen belt. So
it will not coast in LEO.

So in my reading of the press kit, it would be an initial ascend into LEO (at
say ~200 km altitude apogee) towards its first nodal crossing: and the burn
00:28:52 after launch would then correspond to an insertion burn into something
GTO-like at the first nodal crossing, over Africa (the timing agrees to a burn
at the first nodal crossing for an ~200 km initial orbit insert).

So something (*very approximately only*) like this 200 * 36000 km GTO orbit:

FALCON H SECO 2 option 1
1 70000U 18999A   18037.79087963  .00000000  00000-0  00000-0 0    04
2 70000 023.4400 077.4998 7311824 000.5329 359.9906 02.26675333    07

The problem with this, as Jonathan McDowell has pointed out, is that a 3rd boost
into heliocentric orbit after 6 hours (half an orbit) near 01:00 UT at apogee of
such a GTO-like orbit, would boost it into the inner solar system, not out
towards Mars orbit. Unless they boost 180 degrees opposite to the orbital
direction of movement at that moment (but that would be odd).

So Jonathan's proposal of a lower ~200 x 20000 km orbit and 3rd burn around
00:50 UT into heliocentric Mars-bound orbit at perigee of this alternative
orbit, after one full revolution, might be an option. Something (*very
approximate only*) like this:

FALCON H SECO 2 option 2
1 70001U 18999A   18037.79087963  .00000000  00000-0  00000-0 0    05
2 70001 023.4400 077.4998 6006829 000.5329 359.9829 04.10387945    01

This would also have it coast through the center of the Van Allen belt.

After the 3rd boost, the resulting heliocentric orbit would then be an Apollo
orbit, something *extremely approximately only* like this, based on the average
of the 380-450 million km earth distance mentioned by Musk:

Tp   2458156.53472
q    0.986  AU
a    1.37   AU
e    0.28
i    0.0-1.5
om   360.0
node 137.938
Q    1.75 AU

Note: this is all conjecture and certainly not accurately enough to point a
telescope at the heliocentric departure orbit.


- Marco



-----
Dr Marco Langbroek  -  SatTrackCam Leiden, the Netherlands.
e-mail: sattrackcam_at_langbroek.org

Cospar 4353 (Leiden):     52.15412 N, 4.49081 E (WGS84), +0 m ASL
Cospar 4355 (Cronesteyn): 52.13878 N, 4.49937 E (WGS84), -2 m ASL
Station (b)log: http://sattrackcam.blogspot.com
Twitter: _at_Marco_Langbroek
-----
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Received on Tue Feb 06 2018 - 06:37:50 UTC

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