Orbital Mechanics

Is there someone here who can do a short lesson on orbital mechanics please.

I understand faster launch speed = higher orbit = slower orbital speed and
the reverse.

I am having trouble with object 1 is x miles from object 2.
Object 3 is x miles from object 2. Same distance.

If object 1 adds 10 units of delta V in can get to object 2 in 24 hrs.

object 3 can only add .5 units of delta v. It can not get to object ever.

Thanks

"JOE HECHT" wrote in message
ink.net...
Is there someone here who can do a short lesson on orbital mechanics
please.


The 'Orbitology' chapter in my book 'Space Power Theory' is online
as a pdf file at my home page www.jamesoberg.com, it was
written for military officers to understand, give it a try.

In article . net,
JOE HECHT wrote:

Is there someone here who can do a short lesson on orbital mechanics please.

I understand faster launch speed = higher orbit = slower orbital speed and
the reverse.

I am having trouble with object 1 is x miles from object 2.
Object 3 is x miles from object 2. Same distance.

If object 1 adds 10 units of delta V in can get to object 2 in 24 hrs.

object 3 can only add .5 units of delta v. It can not get to object ever.

Thanks

GROSSLY INSUFFICIENT data for any sort of detailed analysis.

If the objects are in orbit, then either their existing orbits
intersect, or they do not.

If the orbits intersect, then one change-of-motion will place the
two objects in the same orbital path. They may be in different _places_
in the orbit, but they are in the same orbital path.

If the initial orbits do not intersect, then a change-of-motion is
required to place one of the objects into an intersecting orbit, whereupon
the problem devolves into the 1st case.

Once they are in different places in the same orbit, _two_ change-of-motion
actions are required to synchronize the objects -- one to change to a
faster/slower co-planar orbit and the second to move back to the original
orbit at the 'right time'.

Any of those 'change-of-motion' steps requires a fixed delta-V, determined
by the orbital parameters. Use either too much, or too little, and you
end up in the wrong place at the wrong time, going in the wrong direction.

in the first 2 situations, you can use 'excess' delta-V to change orbits,
so that you arrive at the 'intersection' point sooner. When you do that,
you have to use _more_ delta-V to make the change to the target orbit,
than you would if you had waited to arrive there in the initial intersecting
orbit.

*ONCE* you are in the same orbit, _any_ amount of delta-V (properly applied)
will let you synchronize with the other object, if you can allow enough time
between the two change-of-motion events. To catch up with the other object
at a specified point, or (equivalently) at a specified time, requires a fixed
delta-V -- only by allowing the time-frame/position to vary, can you accomplish
the result with differing delta-v.

If the change-of-motion required to get _into_ the common orbit, from the
current one, is greater than the available delta-V, well, "you can't get
there from here" applies.


For an extreme example, consider 'object 1' in a 1000 km high, circular,
equatorial orbit. consider 'object 2', also in an equatorial orbit (thus
co-planar), with a 1000km apogee/900km perigee; with orbital constants
such that when it next reaches apogee it will be co-incident with 'object 1',
and that it is *now* at perigee. consider 'object 3' in a 900 km circular
*polar* orbit (with a -zero- 'side velocity', in the equatorial plane), with
its current position co-incident with 'object 2'.

Both object 2 and object 3 are equidistant from object 1. (They have to
be, they're in the same place!

On 1/4 orbit, object 2 will be (at least momentarily) co-incident with
object 1, with -zero- expenditure of delta-V. Then it merely has to
expend enough delta-V to change into the circular orbit. By expenditure of
'some' additional delta-V, object 2 can become co-incident with object 1
sooner. How much sooner depends on the available delta-V, limited by the
rate at which it can be applied.

On the other hand, object 3 would have to kill all it's polar orbit velocity
component, and _add_ a similar equatorial-orbit velocity component, *and*
add enough velocity to convert the 900 km circular orbit to a 1000 km apogee
one. the first part of the operation (transferring from polar orbit to
equatorial) requires a delta-V of sqrt(2)*orbital_velocity. Changing out
of the circular orbit to the elliptical one is trivial by comparison. As in
the first case, once it is co-incident with object 1, it has to expend the
delta-V to change into the circular orbit.

If you just want the items to 'get to' each other -- i.e., 'at the same
place, at the same time' without regard to relative direction and/or
velocity, the possibilities are messier. But....

Consider:
Object 2 in the same _circular_ orbit as Object 1, X miles behind it.
Object 3 in an orbit that is 'perpendicular' (e.g polar vs equatorial)
to the orbit of Object 1, in a circular orbit X miles lower, with
Object 3 _directly_ below Object 1, *now*.

Object 2 can 'catch up' with Object 1, by dropping into a lower co-planer
orbit, waiting the appropriate amount of time, and raising back to the
original orbit. Amount of delta-V required depends on the time available.
Allowing enough time, an infinitesimal delta-V will do the job.

Object 3 must get into an orbit with an apogee that is X miles higher than
it's current circular one, to have _any_ chance of 'getting to' Object 1.
The 'least expensive' change-of-motion that accomplishes this will result
in a perigee that is X miles _lower_ than the current orbit. If Object 3
does not have enough delta-V to accomplish this change of motion, there is
no possible way for it to 'get to' Object 1.

Once it _does_ get into an orbit with the requisite apogee, there is still
the matter of synchronizing the timing, so that it and Object 1 arrive 'at
the same place at the same time'. This _may_ be accomplished simply by
waiting (if you're willing to wait long enough), or it may be necessary to
expend some additional delta-V to allow an 'eventual' meet. In any case,
additional delta-V can make the meet occur sooner.

Thanks for pointing me to the link.

I also saw your video interview with Discovery Canada. That explains also
why my thoughts are wrong.

Do we have a multistage elv that could be fitted with an adapter to dock
with and then change Hubble's orbit to something more friendly with ISS?

It seems the $ decision to close African emergency landing sites is kind of
a self fulfilling thing to force flights to ISS. I do not know International
politics to debate political reasons.

Security. If we send 1 MEU to secure site from say a week before launch
until orbit or landing it can be secure. Can the shuttle be transported from
Africa back to the US on the STA anyway? If not, then what if an Africa or
any other Non US abort landing?

"Jim Oberg" wrote in message
...

"JOE HECHT" wrote in message
ink.net...
Is there someone here who can do a short lesson on orbital mechanics
please.


The 'Orbitology' chapter in my book 'Space Power Theory' is online
as a pdf file at my home page www.jamesoberg.com, it was
written for military officers to understand, give it a try.

In message . net, JOE
HECHT writes
Thanks for pointing me to the link.

I also saw your video interview with Discovery Canada. That explains also
why my thoughts are wrong.

Do we have a multistage elv that could be fitted with an adapter to dock
with and then change Hubble's orbit to something more friendly with ISS?

But surely you don't want to change the orbit to something close to ISS.
If you did, the mirror would be covered in poo.

But surely you don't want to change the orbit to something close to ISS.
If you did, the mirror would be covered in poo.

hubble could be wrapped in a big bag or blanket to minimize mirror
contamination
HAVE A GREAT DAY!

(bob haller) wrote in
:


But surely you don't want to change the orbit to something close to ISS.
If you did, the mirror would be covered in poo.

hubble could be wrapped in a big bag or blanket to minimize mirror
contamination

Yeah, I'm sure they'll be able to take great pictures through that bag,
too.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

Jim Oberg wrote in message
...

"JOE HECHT" wrote in message
ink.net...
Is there someone here who can do a short lesson on orbital mechanics
please.


The 'Orbitology' chapter in my book 'Space Power Theory' is online
as a pdf file at my home page www.jamesoberg.com, it was
written for military officers to understand, give it a try.

That was actually quite good. I now understand something that baffled me in
physics class years ago. It's all in the angular momentum...
Thanks for posting the link.