Re: SPACE: ISS (and Other) Thoughts

From: Michael M. Butler (
Date: Fri Oct 20 2000 - 23:25:51 MDT wrote:
> <> How much of a delta-v penalty does the STS pay in reaching that high
> inclination?

I don't exactly know, but here's a starting point:

Using OV-103, basic cargo lift for due east from KSC (which is located
at 28.5 deg N) to 110
nm orbit was said to be 55,000 lbs (pre-Challenger figures). Subtract
about a ton from that for the post-Challenger firepole, etc.; this
brings us to a nominal 53,000 lbs to 110 nm.

For the same altitude, subtract 500 pounds per degree of plane change,
according to an old page I found via Google:

ISS is as you know at 51.6 degrees, so based on that rule of thumb, we
are talking about a roughly -11,500 lb penalty just to get to a minimal
orbit at that inclination.

Unfortunately, I do not know what this translates to for a launch to the
same inclination, but 354 km up. I could work a rough guess with the
help of my old pal Kepler, but I'm too tired to be sure I'd done it
right. Anyone? Bueller?

Anyway, as you no doubt know, the whole rationale for the 51.6-degree
orbit was so the Russkis (/Kazakhs) could do all the heavy lifting with
maximal payloads launched due east. Shuttle wasn't ever supposed to get
its nails dirty with cargo.

> <> Suppose someone actually uses the ISS for one of the primary original
> purposes envisioned in the Original Plan, i.e. as a construction and
> maintenance base for further space infrastructure, such as a reusable
> translunar vehicle, planetary transit vehicles and the like. How much
> penalty is imposed by its current orbit?

Well, excluding the lift penalty, I think it is going to be damned
painful if you want to do a plane change near in--my gut says delta vee
in the several (3? 5?) miles per second range. So putting geostationary
comsats in service from ISS is A Bad Idea.

OTOH, flying single destination missions 'way out of the plane of the
ecliptic seems quite possible to me; if you want to, say, stroll around
the asteroid belt, you can do the plane change with an astute gravity
assist if you care to time it right. This is assuming current propulsion
tech. Lightsails or Orion (yeah, right!) change matters considerably, of

Some space industrialists say the most serious problem with the higher
inclination orbit is that the Shuttle can't spare the juice to nudge the
ETs into a parking orbit for later use as building blocks.

> <> Suppose things change in the future and it makes sense to move the ISS to
> a more equatorial orbit. Will the propulsion system the final version will
> have be able to make that move?

That's up in the air, no pun intended. Since ISS is intended to be
boostable with a specific module that mates with the rest of the system,
there is no reason aside from money and politics why it couldn't. If
you're in a hurry, some parts of the Conestoga might flap in the breeze,
so to speak. And the moments of inertia on that collection of...
stuff... might make the control model a bit weird.

My nickle,


Shows a kewl Atlantis cockpit worthy of Kubrick and Clarke.

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