TDRS-1, TDRS-3, and TDRS-4 were all released from orbiters that had
insertion orbits in the neighborhood of 175 nm. (I'm not sure if all
of those were elliptical.)

TDRS-2, however, was to be released from Challenger after Mission 51-L
had reached a circular insertion orbit of about 150 nm.

Orbital mechanics is not my strongest suit, At any rate, I'm looking
for a dumbed-down explanation of the apparently unique insertion orbit
planned for Mission 51-L's release of TDRS-2.

TDRS-1, TDRS-3, and TDRS-4 were all released from orbiters that had
insertion orbits in the neighborhood of 175 nm. (I'm not sure if all
of those were elliptical.)

TDRS-2, however, was to be released from Challenger after Mission 51-L
had reached a circular insertion orbit of about 150 nm.

Orbital mechanics is not my strongest suit, At any rate, I'm looking
for a dumbed-down explanation of the apparently unique insertion orbit
planned for Mission 51-L's release of TDRS-2.

JTM

TDRS-1, TDRS-3, and TDRS-4 were all released from orbiters that had
insertion orbits in the neighborhood of 175 nm. (I'm not sure if all
of those were elliptical.)

TDRS-2, however, was to be released from Challenger after Mission 51-L
had reached a circular insertion orbit of about 150 nm.

Orbital mechanics is not my strongest suit, At any rate, I'm looking
for a dumbed-down explanation of the apparently unique insertion orbit
planned for Mission 51-L's release of TDRS-2.


I'd look at launch mass and see if there's a significant difference there.


For a geosynch orbital insertin, 175 nm vs. 150 nm probably isn't that much
of a difference, but for a "1st stage" it can be.

As I recall TDRS-A was released and immediately had problems. It never
achieved the desired orbit and was of marginal use at best.

On Sun, 13 Apr 2008 20:44:14 -0400, "Greg D. Moore \(Strider\)"
mooregr_deleteth1s@greenms.com> wrote:



TDRS-1, TDRS-3, and TDRS-4 were all released from orbiters that had
insertion orbits in the neighborhood of 175 nm. (I'm not sure if all
of those were elliptical.)

TDRS-2, however, was to be released from Challenger after Mission 51-L
had reached a circular insertion orbit of about 150 nm.

Orbital mechanics is not my strongest suit, At any rate, I'm looking
for a dumbed-down explanation of the apparently unique insertion orbit
planned for Mission 51-L's release of TDRS-2.


I'd look at launch mass and see if there's a significant difference there.


For a geosynch orbital insertin, 175 nm vs. 150 nm probably isn't that much
of a difference, but for a "1st stage" it can be.


I see M*xs*n is still busily trying to convince the bystanders that he
has a clue.

Don't forget that 51L also carried Spartan-Halley. 51L was
significantly heavier than STS-6 or STS-26.

There's your difference.

On Apr 13, 3:11 pm, "max...@mission51l.com" <max...@mission51l.com
wrote:

TDRS-1, TDRS-3, and TDRS-4 were all released from orbiters that had
insertion orbits in the neighborhood of 175 nm. (I'm not sure if all
of those were elliptical.)

TDRS-2, however, was to be released from Challenger after Mission 51-L
had reached a circular insertion orbit of about 150 nm.

Orbital mechanics is not my strongest suit, At any rate, I'm looking
for a dumbed-down explanation of the apparently unique insertion orbit
planned for Mission 51-L's release of TDRS-2.

As I recall TDRS-A was released and immediately had problems. It never
achieved the desired orbit and was of marginal use at best.

TDRS'es are made up of three components, a TDRS-east, TDRS-west and
TDRS-spare. Those plus the ground system make up TDRSS.

TDRS-A eventually became TDRS-spare after the successes of TDRS-C and
D. (Note you use the number designations of which letters were
actually used -i.e. TDRS-1 is TDRS-A, TDRS-2 is TDRS-B, and so on.). I
have lost count where we are right now.

TDRSes orbits, being geo-stationary, are or should be as circular as
possible. They should float above the earth and orbit at exactly 23hr
56min 4sec per revolution (1 day). Lastly, they tend to jiggle in sort
of a figure-8 over their prime spots and occasional burns are needed
to keep them in true geosynchronous position.

STS-6 (with two OMS burns, as planned for 51-L) was launched well
prior to the first DOI (41-C). I don't recall offhand if the STS-6
insertion orbit was circular or elliptical. (I'm looking for more
details on that, as well as STS-29.)

TDRS-1, TDRS-3, and TDRS-4 were all released from orbiters that had
insertion orbits in the neighborhood of 175 nm. (I'm not sure if all
of those were elliptical.)

TDRS-2, however, was to be released from Challenger after Mission 51-L
had reached a circular insertion orbit of about 150 nm.

Orbital mechanics is not my strongest suit, At any rate, I'm looking
for a dumbed-down explanation of the apparently unique insertion orbit
planned for Mission 51-L's release of TDRS-2.

All the IUS really cares about is that the line of
nodes of the orbit should be aligned with the GSO
target at the time of IUS ignition. That drives launch
window but not altitude.

DI vs. SI makes no difference. In either case, the OMS-2 burn is used to
circularize the orbit on non-rendezvous missions, so the orbit is no
longer elliptical at the time of IUS deploy.

maxson@mission51l.com> wrote in message
news:b4faea56-02d8-45de-9b63-7554f99c9d21@k13g2000hse.googlegroups.com...
TDRS-1, TDRS-3, and TDRS-4 were all released from orbiters that had
insertion orbits in the neighborhood of 175 nm. (I'm not sure if all
of those were elliptical.)

TDRS-2, however, was to be released from Challenger after Mission 51-L
had reached a circular insertion orbit of about 150 nm.

Orbital mechanics is not my strongest suit, At any rate, I'm looking
for a dumbed-down explanation of the apparently unique insertion orbit
planned for Mission 51-L's release of TDRS-2.


I'd look at launch mass and see if there's a significant difference there.

For a geosynch orbital insertin, 175 nm vs. 150 nm probably isn't that much
of a difference, but for a "1st stage" it can be.

On Sun, 13 Apr 2008 18:17:49 -0700 (PDT), Eric Chomko

pne.cho...@comcast.net> wrote:
As I recall TDRS-A was released and immediately had problems. It never
achieved the desired orbit and was of marginal use at best.

Your recollection is faulty. TDRS-A had an IUS malfunction, but was
nurse-maided to its operational orbit via onboard thrusters in time to
support STS-9/Spacelab 1 seven months later. It was eventually
replaced by the later TDRS's and started getting other duties, such as
relay support for Antarctica research stations.

On Apr 13, 11:43 pm, Brian Thorn <bthor...@suddenlink.net> wrote:

On Sun, 13 Apr 2008 18:17:49 -0700 (PDT), Eric Chomko

pne.cho...@comcast.net> wrote:
As I recall TDRS-A was released and immediately had problems. It never
achieved the desired orbit and was of marginal use at best.

Your recollection is faulty. TDRS-A had an IUS malfunction, but was
nurse-maided to its operational orbit via onboard thrusters in time to
support STS-9/Spacelab 1 seven months later. It was eventually
replaced by the later TDRS's and started getting other duties, such as
relay support for Antarctica research stations.

Fromhttp://spaceflightnow.com/atlas/ac139/000626tdrs.html:

Current status: After years of operation, NASA removed TDRS-1 from
full-time service at its 49 degrees West longitude slot due to its
degraded health. Today the craft provides part-time coverage of the
Antarctic region in support of the National Science Foundation. Its
orbit is currently inclined 10.5 degrees.

Okay, the fact that it has a current status at all makes it better
than I had thought. I do recall that at the time it was launched, they
knew THEN that it was going to be TDRS-spare and replaced by the next
two successful TDRSes because of its problem.

Surely after TDRS-B's fate TDRS-A didn't seem so bad. Certainly not as
bad as it did when it was the lone TDRS flying.

DI vs. SI makes no difference. In either case, the OMS-2 burn is used to
circularize the orbit on non-rendezvous missions, so the orbit is no
longer elliptical at the time of IUS deploy.