Re: Ephemerides for Falcon Heavy hardware?

From: Matija Perne via Seesat-l <seesat-l_at_satobs.org>
Date: Tue, 6 Feb 2018 14:47:53 +0100
2018-02-06 13:36 GMT+01:00 Marco Langbroek via Seesat-l <seesat-l_at_satobs.org>:
> 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

I believe one way of reaching an Apollo orbit like the one proposed is
boosting the object in the direction of Earth's travel around the Sun.
A GTO-like orbit that is reached through an insertion burn over Africa
00:28:52 after launch has its apogee in front of the Earth, generally
speaking. Assuming the boost to heliocentric orbit is approximately
parallel with the direction of travel, it would thus happen on the way
towards the apogee of the GTO-like orbit. For the rocket to be there 6
hours after launch, the GTO-like orbit could have its apogee higher
than a GTO would, so it is not reached yet by then.

Matija
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Received on Tue Feb 06 2018 - 07:49:06 UTC

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