[FPSPACE] ISS & interplanetary flights

[Saunders B.Kramer Sr.]

Hi Jim : Nice of you to get the details on mass losses re 
interplanetary flights commencing at the ISS. I've always been aware of 
such losses but it occurs to me that real, low risk flight will (1) 
have a larger crew than most persons contemplate, (2) will have a 
larger spacecraft than almost anyone presently contemplates hence it 
(a) will have to be assembled over a period of months including 
detailed checkout and (b) will have excess propulsion capability. [ by 
the way, last time he was asked Roald Sagdeyev stated that he thought 
such a spacecraft would 'weigh' in at 2500 metric tons. by coincidence 
in my sf novel "The Hundred Billion New-Ruble Trip" (a Russian landing 
on Mars) has a spacecraft of just that size. While the novel is sf all 
the propulsion capabilities expressed in the tale are real for that 
size ship - I laid out a design for 6 months before I wrote a word.]
Insofar as crew size is concerned, t'is related to risk but that's 
another story.
Best Regards & Very Happy Holiday
Saunders
On Dec 21, 2004, at 3:29 PM, Jim Oberg wrote:

> Let me retreat a bit from my earlier position.
>
> The biggest penalty is going to 52 degrees -- the space shuttle loses 
> about
> a quarter of its payload capacity. However, launch of a cargo cannister
> alone, or rocket component, suffers less markedly -- perhaps 3 to 4 % 
> in
> terms of insertion energy required (partially lost advantage of 
> eastward
> earth spin). The difference is that of the entire shuttle stack at
> insertion -- empty orbiter (220,000 lbs), ET (80,000 lbs), and payload
> (40,000 lbs), total 340,000 lbs, the 3% penalty (say 10,000 lbs) must 
> ALL
> come out of the payload. For a cargo cannister and propulsion module of
> empty weight 12,000 lbs and cargo weight of say 28,000 lbs 
> (hypothetical),
> total of 40,000 lbs into 28deg orbit, going to 52 degrees costs 3% or 
> 1,200
> lbs, which is about 4% of the usable payload -- probably tolerable. The
> difference is in the 'payload fraction' versus 'non-negotiable 
> re-usable'
> fraction.
>
> However, 28 degrees remains attractive for max performance, and if 
> human
> crews are needed for occasional servicing, they can launch aboard 
> Soyuzes
> from Kourou and use a temporary 'construction shack' -- the same kind 
> of
> 'safe haven' that NASA ought to consider launching to support a shuttle
> repair of Hubble.
>
>
>
>
>
> ----- Original Message -----
> From: "Saunders B.Kramer Sr." <sbetk5 at earthlink.net>
> To: "Keith Gottschalk" <kgottschalk at uwc.ac.za>
> Cc: <fpspace at friends-partners.org>
> Sent: Tuesday, December 21, 2004 2:11 PM
> Subject: Re: [FPSPACE] ISS & interplanetary flights
>
>
>> I seem to recall that once away from the strong gravitational 
>> influence
>> of Earth getting back to the ecliptic should not be a big deal in 
>> terms
>> of propulsion. Isn't that so? And 2  Future trips, when nuclear
>> propulsion is available, when we do not have to go using Hohmann
>> transfer we will have excess propulsion to allow Xfer  from high
>> inclination orbits to the ecliptic. There is something of a trade-off 
>> :
>> assemble and check out before launch at a space station (vz. the ISS)
>> that has all the facilities for such functions or do the
>> assembling/checkout without a station. That requires a long detailed
>> study.
>> Saunders
>> On Dec 21, 2004, at 6:00 AM, Keith Gottschalk wrote:
>>
>>>>>> [snip] The performance penalty for going
>>>> up to a high-inclination orbit and then having to go back into the
>>>> ecliptic
>>>> for interplanetary trajectories is very high. [snip]
>>>> Far better to stage out of 28 deg due east from KSC. If you need a
>>>> Russian-launched component, rendezvous on the way out to Mars.
>>>
>>>      JimO reminds us that in space exploration, equations are
>>> She-Who-Must-be-Obeyed.
>>> [grin]
>>> His point implies that, apart from KSC, cooperative international
>>> interplanetary launches are limited to Kourou, Alcantara, 
>>> Sriharikota,
>>> Sea launch, & the southernmost of the Chinese launch pads. Kourou is
>>> building a Soyuz launch pad. Time will tell whether they will add to
>>> that, a decade hence, a Proton or Angara launch pad.
>>>
>>>    I think - subject to correction by the mathematicians on this 
>>> forum
>>> - that there is that famous circum-Lunar gravity assist manoeuvre to
>>> get your plane twisted back closer to the equator. But is that not
>>> only propellant efficient if limited to GSO rather than the LEO space
>>> station?
>>>
>>>      There is a problem with "If you need a Russian-launched
>>> component, rendezvous on the way out to Mars", unless this refers to
>>> an entire, intact, parallel Russian spacecraft in a small fleet
>>> co-flying to Mars.  LEO provides your only real, in-vacuum test, that
>>> everything is in working order, & docks together in actuality.
>>>
>>>      Perhaps this is going to require Russian interplanetary
>>> components to be launched from Kourou? Only the ESA & Sea Launch, not
>>> Brazil, India, China, can afford to pay the costs of building such a
>>> launch pad. In fact, presumably Sea Launch could do their thing 10 or
>>> 20 kms offshore from Cape Canaveral simultaneously with a KSC launch?
>>>
>>> Keith
>>>
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>>
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