Flight Day 1 redezvous with Space Station altitude targeting ( Orbital mechanics folks...

Please don't insert names in quotes it sounds complete gibberish!

Brian

--
Brian Gaff....Note, this account does not accept Bcc: email.
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________________________________ __________


"John Stoffel" wrote in message
...
"Henry" == Henry Spencer writes:

Henry It's possible to rendezvous not just on the first day, but on
Henry the first *orbit* -- it was done by Gemini -- but unless you
Henry use air launch (or just possibly water launch) to vary the
Henry launch location, or have a lot of spare fuel to play orbital
Henry games, or are located on the equator and launching into an
Henry equatorial orbit, it's impractical. And first-day isn't a
Henry whole lot better. Everything has to be just right, which means
Henry very infrequent launch windows, and the windows are also very
Henry short, because there's no slack in the schedule once you lift
Henry off.

How much extra fuel would you need to carry to achieve an earlier
rendezvous, but without seriously impacting the launch window size?
Or would the orbital mechanics of going to a higher/slower orbit and
then dropping back down to match cost too much in terms of payload
performance?

Since fuel is cheap, why not spend it to cut down on the time, which
isn't cheap in some sense.

John

Since fuel is cheap, why not spend it to cut down on the time, which
isn't cheap in some sense.

Because while fuel itself is cheap, "fuel in orbit" is simply mass
until it
gets to orbit, and mass to orbit is NOT cheap.

Right, plus the fact that the amount of fuel needed to change orbit
parameters gets real big real fast, based on earlier discussions on the
topic. And as Herb relates, fuel is cheap, but lifting it isn't.



--
Posted via a free Usenet account from http://www.teranews.com

"Revision" wrote in message
.. .

Since fuel is cheap, why not spend it to cut down on the time, which
isn't cheap in some sense.

Because while fuel itself is cheap, "fuel in orbit" is simply mass until
it
gets to orbit, and mass to orbit is NOT cheap.

Right, plus the fact that the amount of fuel needed to change orbit
parameters gets real big real fast, based on earlier discussions on the
topic. And as Herb relates, fuel is cheap, but lifting it isn't.

The time to remember "fuel is cheap" is when designing a launch vehicle.
LOX especially is cheap since it's made from air, which is why I'm constant
puzzled by people who think hypersonic air breathing engines for launch
vehicles are a good idea.

Jeff
--
"They that can give up essential liberty to obtain a
little temporary safety deserve neither liberty nor
safety"
- B. Franklin, Bartlett's Familiar Quotations (1919)

Jeff Findley wrote:

"Revision" wrote in message
.. .

Since fuel is cheap, why not spend it to cut down on the time, which
isn't cheap in some sense.

Because while fuel itself is cheap, "fuel in orbit" is simply mass until
it
gets to orbit, and mass to orbit is NOT cheap.

Right, plus the fact that the amount of fuel needed to change orbit
parameters gets real big real fast, based on earlier discussions on the
topic. And as Herb relates, fuel is cheap, but lifting it isn't.


The time to remember "fuel is cheap" is when designing a launch vehicle.
LOX especially is cheap since it's made from air, which is why I'm constant
puzzled by people who think hypersonic air breathing engines for launch
vehicles are a good idea.

Jeff

It's not the cost of the fuel that is the issue. It's the oxidizer's
volume and mass. The design problem would be unchanged if both LOX and
the fuel (eg. LH2) were free.

Sylvia.

On Wed, 7 Feb 2007 23:58:53 -0600, Sylvia Else wrote
(in article ) :

It's the oxidizer's
volume and mass. The design problem would be unchanged if both LOX and
the fuel (eg. LH2) were free.

It's not just the oxidizer. ALL mass to orbit is expensive - fuel, oxidizer,
crew rations, etc. Period.

--
You can run on for a long time,
Sooner or later, God'll cut you down.
~Johnny Cash

Sylvia Else wrote:

Jeff Findley wrote:

"Revision" wrote in message
.. .

Since fuel is cheap, why not spend it to cut down on the time, which
isn't cheap in some sense.

Because while fuel itself is cheap, "fuel in orbit" is simply mass until
it
gets to orbit, and mass to orbit is NOT cheap.

Right, plus the fact that the amount of fuel needed to change orbit
parameters gets real big real fast, based on earlier discussions on the
topic. And as Herb relates, fuel is cheap, but lifting it isn't.


The time to remember "fuel is cheap" is when designing a launch vehicle.
LOX especially is cheap since it's made from air, which is why I'm
constant puzzled by people who think hypersonic air breathing engines for
launch vehicles are a good idea.

Jeff

It's not the cost of the fuel that is the issue. It's the oxidizer's
volume and mass. The design problem would be unchanged if both LOX and
the fuel (eg. LH2) were free.


If the launch window is 9 minutes, and the ISS is in a 90 minute orbit, then
the Shuttle would be able to rendezvous with ISS in half a rev 10% of the
time. How many hours are left after launch in Flight Day 1?

Herb Schaltegger wrote:

On Wed, 7 Feb 2007 23:58:53 -0600, Sylvia Else wrote
(in article ) :


It's the oxidizer's
volume and mass. The design problem would be unchanged if both LOX and
the fuel (eg. LH2) were free.


It's not just the oxidizer. ALL mass to orbit is expensive - fuel, oxidizer,
crew rations, etc. Period.


Well, yes, but building an airbreathing vehicle doesn't reduce the mass
of the crew's rations.

Sylvia.

On Thu, 8 Feb 2007 16:55:42 -0600, Sylvia Else wrote
(in article ) :

Herb Schaltegger wrote:

On Wed, 7 Feb 2007 23:58:53 -0600, Sylvia Else wrote
(in article ) :


It's the oxidizer's
volume and mass. The design problem would be unchanged if both LOX and
the fuel (eg. LH2) were free.


It's not just the oxidizer. ALL mass to orbit is expensive - fuel,
oxidizer,
crew rations, etc. Period.


Well, yes, but building an airbreathing vehicle doesn't reduce the mass
of the crew's rations.

Airbreathing vehicles have so many other design and mass issues that quickly
complicate things WAY beyond the simple design of a bipropellant rocket
vehicle and the mass of oxidizer necessary (most of which is burned along the
way).

Sylvia.



--
You can run on for a long time,
Sooner or later, God'll cut you down.
~Johnny Cash

Craig Fink wrote:

Sylvia Else wrote:

Jeff Findley wrote:

"Revision" wrote in message
.. .

Since fuel is cheap, why not spend it to cut down on the time, which
isn't cheap in some sense.

Because while fuel itself is cheap, "fuel in orbit" is simply mass
until it
gets to orbit, and mass to orbit is NOT cheap.

Right, plus the fact that the amount of fuel needed to change orbit
parameters gets real big real fast, based on earlier discussions on the
topic. And as Herb relates, fuel is cheap, but lifting it isn't.


The time to remember "fuel is cheap" is when designing a launch vehicle.
LOX especially is cheap since it's made from air, which is why I'm
constant puzzled by people who think hypersonic air breathing engines
for launch vehicles are a good idea.

Jeff

It's not the cost of the fuel that is the issue. It's the oxidizer's
volume and mass. The design problem would be unchanged if both LOX and
the fuel (eg. LH2) were free.


If the launch window is 9 minutes, and the ISS is in a 90 minute orbit,
then the Shuttle would be able to rendezvous with ISS in half a rev 10% of
the time. How many hours are left after launch in Flight Day 1?

blink


blink blink

That is, with what is essentially the current propellent budget for
rendezvous. No additional propellent. Essentially what we have today with
the Space Shuttle going to the International Space Station. If the Launch
Window is 9 minutes.

The Launch Window is the plane control, it is the time that it takes the
plane of the Space Station to sweep across the Launch site as the Earth
rotates. The Shuttle can launch into a plane that is four or five minutes
East or West of the launch site with it's current rendezvous propellent
budget.

Assuming no phase control, then Space Station is at a random position in
it's 90 minute orbit. This yields a 10% chance of rendezvous on the first
orbit.

The probability can be increased to 20% by adding the other daily launch
opportunity. This opportunity is never considered because the launch site
of the Space Shuttle is not in an ideal location and is constrained by ...