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Agamemnon

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Posts posted by Agamemnon

  1. Just read this on the Guardian.

    It says Philae will be told to hop. From what I gathered from the Google thing this afternoon, they were considering it, but it seems risky. Does anyone have more info? It wouldn't surprise me if the article is wrong, as it states that Philae "has been resting on its side", which is entirely incorrect.

    iirc,

    as they are done with all science (and primary objectives) they can get (resp. they will be if the drill worked and they will get data in the evening in the next comm window)...

    they will risk it and try to change the lander position to get more sunlight

  2. The Merlin 1D Vacuum is very efficient, for a kerosene engine

    it is effiecient for a gas generator kerolox...

    not so much for a kerolox in general - eg. there is a staged combustion kerolox engine (routinely used today) optimised for high thrust (not for isp) and for use on first stages that has nearly the same isp as merlin 1d vac optimised for high isp (the engine is rd-180 with vac isp 338 s)

    there is an isp optimized kerolox engine used in soyuz 2-1b upper stage with isp 359 s (rd-0124)

  3. the reason being that it uses quite crappy upper stage engine - quite low specific impulse for an upper stage - for m1d vac it is only 340 s... and the more energetic orbit (gto, geo, escape) you are targeting the better isp is required or you are getting quite harsh payload penalties...

    ariane 5 or atlas 5 uses hydrolox upper stage engines with specific impulse around 440-450 s (btw - russian staged combustion kerolox upper stage engines have isp close to 360 s)

    so... using better upper stage engine would help (eg. ariane, atlas, delta)... using 3rd stage would help too (eg. proton)

  4. All Dragons actually launched so far have been part of NASA's CRS contract, which stipulates use of a new capsule every launch.

    actually... acc. to people on nsf, that is not true...

    the contract only says that they get paid as if they launch a new dragon every time... but they could launch a recycled one, if they are confident enough that it would work...

  5. basically...

    it is not so simple...

    this shortened randezvous profile needs better (more precise) orbital insertion from the launcher and usually needs an iss maneuver to better align the orbit before the launch... the launch time/date needs to be more precise to correctly align the phase angles... etc

    and btw -

    during the two day profile the cosmo/astronauts can use the orbital part of the soyuz - provides additional space, some sleeping space, wc, etc...

  6. Congrats to Ariannespace though. Big competition with SpaceX though... and I think SpaceX is actually in the lead, or will be shortly.

    except spacex is not even in the competition at the moment...

    on the other hand - arianne 5 holds cca 50% of commercial gto market... competition is between arianne and proton for gto launches (most of commercial launches around the world are to the gto)

    don't believe everything what is said about spacex

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