On Nov 26, 2:32Â*am, Robert Clark wrote:
On Nov 15, 4:57Â*pm, Robert Clark wrote:
...
Â*Interesting suggestion in the comments section on that page:
Phobos-Grunt Mars probe remains silent in Earth orbit.
BY STEPHEN CLARK
SPACEFLIGHT NOW
Posted: November 11, 2011http://www.spaceflightnow.com/news/n1111/11phobosgrunt/
Â*The idea would be to use the X-37B currently in orbit to communicate
with the satellite. It certainly could at least photograph it.
Â* Â*Bob Clark
Â*That idea was by Bruce Behrhorst, contact info:http://www.facebook.com/people/Bruce...00002307375325.
Â*A question is would the X-37b have sufficient delta-V for the
rendezvous? One of the early requirements for the vehicle was for a
delta-V of 3,100 m/s, about 10,000 feet per second, though the actual
value reached in this vehicle hasn't been released.
Â*The X-37b almost certainly has imaging equipment as one of its
reported intentions is to provide orbital surveillance on short notice
for varying locations. However, it is a question whether this can be
used to image satellites. Still, another speculated upon capability
for the X-37b was for it to examine other satellites. See for instance
this page, near the end, in the section "X-40 Space Maneuver Vehicle
(SMV)":
Military Spaceplane
X-40 Space Maneuver Vehicle
Integrated Tech Testbed.http://www.fas.org/spp/military/program/launch/msp.htm
Â*See these pages for the Â*orbital parameters of Phobos-Grunt and the
X-37b:
PHOBOS-GRUNT.http://www.n2yo.com/satellite/?s=37872
OTV 2 (USA 226)http://www.n2yo.com/satellite/?s=37375
Â*See this page for the formulas for the delta-V required for orbital
changes:
ORBITAL MECHANICS.http://www.braeunig.us/space/orbmech.htm#maneuver
Â*The formulas are rather complicated. Â*But a simplified scenario
suggests it might be doable. First, note that unless the altitude
difference is very large, such as between LEO to GEO, then the delta-V
needed to change altitude isn't too great, particularly when its still
in LEO. See for instance this online Hohmann transfer orbit
calculator:
Orbital Transfer Calculator.http://www.vrzone.org/space/orbital_transfer.php
Â*Plugging in the orbital altitudes for Phobos-Grunt and the X-37b
gives a delta-V of 40 m/s.
The largest delta-V would probably be due to the plane change. For a
simplified case of both circular orbits, the formula is:
ΔV = 2Vsin(θ/2) , where θ is the difference in the angle of
inclination, and V is the orbital speed. For a 10 degree angle change
and 7,800 m/s orbital speed, this is ÄV = 1,360 m/s. Considering how
high was planned to be the delta-V capability this is not out of the
question.
Â*Note that for the X-37b that almost certainly has the capability to
image ground sites, you would think Russian sites such as launch sites
should be within its orbital change capability. But then if it has the
capability to reach these high latitude sites then it also has the
capability to reach the orbital inclinations of satellites such as
Phobos-Grunt launched from these sites.
Â* Â* Bob Clark
Note that NASA has recently put out an RFI for robotic, satellite
servicing spacecraft:
NASA Releases RFI for On-Orbit Robotic Spacecraft Servicing.
Posted by Doug Messier on November 4, 2011, at 5:37 am in News
http://www.parabolicarc.com/2011/11/...aft-servicing/
Then Boeing would have an incentive to want to test the capabilities
of the X-37b in this case to showcase its capabilities for the
satellite servicing role.
The calculation above was for a rendezvous. The DoD might not want it
to be known what the delta-V capabilities of the X-37b are. But a
flyby would require much reduced delta-V for brief communications to
be sent to Phobos-Grunt. This then would not reveal what the
capabilities of the X-37b are.
Bob Clark