space shuttle debris

Space Shuttle DebrisPresented by: Evan C. Wayton

Scope• Overview• Contact Models• Tracker Considerations• Simulated Considerations• Simulated Data Results• Conclusions

Scope: Overview• Overview

• Mission• 3-2-1-Blastoff!• Why Study Ascent Debris?

• Nominal Radar Systems• Key Performance Parameters

• Contact Models• Tracker Considerations• Simulated Considerations• Simulated Data Results• Conclusions

Gregory M. Horstkamp, JOHNS HOPKINS APL TECHNICAL DIGEST, VOLUME 29, NUMBER 2 (2010)

Mission: 3-2-1-Blastoff!~Liftoff

Mission: 3-2-1-Blastoff!~4 seconds

Mission: 3-2-1-Blastoff!~19 seconds

Mission: 3-2-1-Blastoff!

http://www.zinkwazi.com/blog/1462/cosmo-skymed-4-satellite-launch-november-5-2010

Mission: Why Study Ascent Debris• STS-107 (Columbia)

February 1, 2003

• What was the debris?

• How do we track ascent debris in the night?

• Why is it important?

Mission: Ascent Debris

https://www.youtube.com/watch?v=IgQ3ekcvyRA#t=21

Nominal Systems (NASA)• July 24, 2014: US Patent 20140203961 A1

• “ A method is provided for analyzing debris events after a launch of a rocket-propelled vehicle. Radar and Doppler data of the launch of the rocket-powered vehicle is collected for a period of time. Atmospheric conditions are determined at the time of launch. A trajectory of the rocket-propelled vehicle is determined during ascent.”

ARDENT: Ascent Radar Debris

Examination Tool

http://www.google.com/patents/US20140203961

Nominal Systems (NASA)• July 24, 2014: US Patent 20140203961 A1

• Columbia Disaster Conclusion• Small briefcase sized foam insulation struck left wing

• Common ascent debris• SRB and SRB exhaust/smoke plumes• Main engine exhaust

• “ During the STS-107 accident investigation, radar data collected during ascent indicated a debris event that was initially theorized to be the root cause of the accident. This theory was investigated and subsequently disproved by the Columbia Accident Investigation Board (CAIB). However, the data itself and the lack of understanding of what debris data in radar meant to the shuttle program, required further analysis and understanding.”

Nominal Systems (Lockheed)• February 7, 2006: US Patent 6995705 B2

• “System and method for doppler track correlation for debris tracking”

Nominal Systems• Land Based C-Band Mid-Course Imaging Radar (MCR)

• “Far enough north” such that the exhaust of SRBs would not impede a potential debris event

• Sea Based X-Band all weather Doppler Radars• Mirror image of C-Band MCR• Head on view of ascent

Kent, B.M. “The NASA debris radar for characterizing static and dynamic ascent debris events for safety of flight,” APSURSI 2012 IEEE

Nominal Systems

Kent, B.M. “The NASA debris radar for characterizing static and dynamic ascent debris events for safety of flight,” APSURSI 2012 IEEE

Key Performance Parameters• This is very interesting, and could

quickly escape the scope of this project

• How can we use what we learned about Kalman filters to track a simplified ascent debris model?• Use a Kalman filter to track shuttle and

shuttle debris• Distinguish shuttle track from SRB

debris track using gating/association

Scope: Overview• Overview• Contact Models

• Dynamics of Target Relative to Radar• Associated Physics• Shuttle Model: STS-124• Solid Rocket Booster Model: STS-124

• Tracker Considerations• Simulated Considerations• Simulated Data Results• Conclusions

Dynamics of Target Relative to Radar

http://space.stackexchange.com/questions/3616/were-space-shuttle-external-tanks-recoverable-and-reusable

Dynamics of Target Relative to Radar

science.ksc.nasa.gov/shuttle/technology/images/tal_abort_2.jpg

Associated Physics• Doppler Shift

• Aside: Lord Rayleigh

• Radar Cross Section (RCS)

• Ballistic coefficient

• Drag/Terminal Velocity

Shuttle Model: STS-124• Launch date: May 31, 2008

• Simplifying Assumption• Entire duration of launch

takes place in a plane

http://www.spaceflightnow.com/shuttle/sts124/fdf/124ascentdata.html

Shuttle Model: STS-124

0 100 200 300 400 500 6000

800Down Range Distance of Shuttle Relative to Launch Pad (RLP) vs. Time

Time Since Launch [sec]

0 100 200 300 400 500 600-10

70Height of Shuttle (RLP) vs. Time

Shuttle

Shuttle Model: STS-124

0 100 200 300 400 500 600 700 800-10

70Height Vs. Down Range Distance (RLP)

Down Range Distance (RLP) [miles]

Shuttle

Solid Rocket Booster (SRB) Model: STS-124• No SRB trajectory data was

available for this flight, except the time of SRB separation• Utilize “typical” trajectory

descriptions for SRB

• (Time, Location of Separation)• (Time, Max Altitude)• (Time, Height Parachute)• (Time, Location of SRB Landing)

http://upload.wikimedia.org/wikipedia/commons/4/42/Srb_splashdown.jpg

No SRB Data Provided• http://www-pao.ksc.nasa.gov/kscpao/nasafact/ships.htm

• SRB hit Atlantic Ocean ~60 miles down range,

• Just so happens that at the time that the height reaches zero, the shuttle has gone 60 miles, so we assume that the DR trajectory of the SRB is the same as that of the shuttle

• This isn’t true, for a number of reasons.

• A pair of SRBs, fully loaded with propellant, weigh about 1.4 million pounds (635,040 kilograms) apiece. They stand 149.2 feet (45.5 meters) tall, and have a diameter of 12 feet (3.6 meters). The boosters in use today are the largest solid propellant motors ever developed for space flight and the first to be used on a manned space vehicle. These boosters will propel the orbiter to a speed of 3,512 miles per hour (5,652 kilometers per hour).

• At approximately two minutes after the Space Shuttle lifts off from the launch pad, the twin SRBs have expended their fuel. The boosters separate from the orbiter and its external tank at an altitude of approximately 30.3 statute miles (26.3 nautical miles/48.7 kilometers) above the Earth's surface. After separation, momentum will propel the SRBs for another 70 seconds to an altitude of 44.5 statute miles (38.6 nautical miles/71.6 kilometers) before they begin their long tumble back to Earth.

0 100 200 300 400 500 6000

800Down Range Distance of Shuttle & SRB Relative to Launch Pad (RLP) vs. Time

ShuttleSRB

0 100 200 300 400 500 600-10

70Height of Shuttle and SRB (RLP) vs. Time

ShuttleSRB

Shuttle and SRB Trajectories

Scope: Overview• Overview• Contact Models• Tracker Considerations

• Tracking Shuttle, SORV• Radar 1• Radar 2

• Simulated Considerations• Gating• Gating and Association

• Simulated Data Results• No gating, or association in time• No gating, or association in 2D spatial • Gating and association

• Conclusions

Tracking: Shuttle, SORV

Radar 1: (xo,yo,zo)=(0,-50,0) [miles]

0 100 200 300 400 500 6000

Time since Launch [sec]

Radial Distance of Shuttle Relative to Radar (RTR) vs. Time

Truth: ShuttleMeasured: ShuttleTracked: Shuttle

0 100 200 300 400 500 6000

Azimuthal Angle (RTR) of Shuttle vs. Time

0 100 200 300 400 500 600-5

Time since Launch [sec]E

Elevation Angle (RTR) of Shuttle vs. Time

0 100 200 300 400 500 6000

X Distance of Shuttle Relative to Radar (RTR) vs. Time

Truth: ShuttleMeasured: ShuttleTracked Polar: Shuttle

0 100 200 300 400 500 6000

Y Distance of Shuttle Relative to Radar (RTR) vs. Time

0 100 200 300 400 500 6000

Time since Launch [sec]Z

Z Distance of Shuttle Relative to Radar (RTR) vs. Time

Tracking: Shuttle SORV

0 100 200 300 400 500 6000

Radial Distance of Shuttle Relative to Radar (RTR) vs. Time

0 100 200 300 400 500 600-60

Azimuthal Angle (RTR) of Shuttle vs. Time

0 100 200 300 400 500 600-4

Elevation Angle (RTR) of Shuttle vs. Time

Tracking: Shuttle SORV

0 100 200 300 400 500 600-800

0 100 200 300 400 500 6000

Shuttle and SRB Trajectories• The radar receives serial measurements

• Without gating and association, it cannot distinguish between shuttle and SRB

• What would happen if the radar tried to track the data without gating and association?

0 100 200 300 400 500 6000

Radial Distance Relative to Radar (RTR) of Shuttle and SRB vs. Time

Truth: Shuttle + SRB Rx DataMeasured: Shuttle + SRB Rx DataTracked: Shuttle + SRB

0 100 200 300 400 500 6000

Azimuthal Angle (RTR) of Shuttle and SRB vs. Time

0 100 200 300 400 500 600-5

Elevation Angle (RTR) of Shuttle and SRB vs Time

Tracking: Shuttle and SRB

0 100 200 300 400 500 6000

Truth: Shuttle + SRBMeasured: Shuttle + SRBTracked Polar: Shuttle +SRB

0 100 200 300 400 500 6000

Tracking: Shuttle and SRB, Cartesian

Tracking Shuttle and SRB: Gating• Perhaps utilizing a gate alone would solve our problem?

With only gating, the tracker would mix up the shuttle and

the SRB tracks!

Gating and Association• Utilizing an EKF gating and association in Cartesian coordinates

could be implemented, due to time constraints, a 3DEKF with gating and association was not implemented

• Association of trajectories crossing with significant parallel component is increasingly difficult with noise present

• How can we implement association without this added complexity?

Gating and Association• Let’s take a look at what our shuttle and SRB data looks like in

Height, Range space

0 200 400 600 800 1000 12000

200Height Vs. Down Range Distance of Shuttle and SRB (RTR)

Down Range Distance (RTR) [miles]

Truth: Shuttle + SRBMeasured Shuttle +SRB

Non-overlapping data, perhaps association will be

easier in this domain?

Gating and Association• Let’s use a 2DRV filter without gating:

0 200 400 600 800 1000 12000

500Height Vs. Down Range Distance of Shuttle and SRB (RTR)

Down Range Distance (RTR) [miles]

Truth: Shuttle + SRBMeasured Shuttle +SRB

Had to use very small η, cannot recover from

continual “zero measurments”

0 100 200 300 400 500 6000

0 100 200 300 400 500 600-5

Azimuthal Angle of Shuttle Relative to Radar (RTR) vs. Time

Gating and Association• Perhaps we could gate/associate Z, Y, and Phi?

0 100 200 300 400 500 6000

Truth: Shuttle + SRBMeasured: Shuttle + SRBGated Track 1Gated Measured Data

0 100 200 300 400 500 6000

0 100 200 300 400 500 600-5

Azimuthal Angle of Shuttle Relative to Radar (RTR) vs. Time

Gating and Association

𝑥=𝑅cos (ϕ ) sin (𝜃 )

𝜃=acos ( 𝑦𝑅cos (ϕ ) )

𝑅=𝑧

sin (ϕ )𝑦𝑧ϕ

If we can track in y, z, and we have solved the tracking problem.

0 100 200 300 400 500 6000

0 100 200 300 400 500 600-5

Elevation Angle of Shuttle Relative to Radar (RTR) vs. Time

Truth: Shuttle + SRBMeasured: Shuttle + SRBGated Track 1Gated Measured DataGated Track 2

Success!

Well… Not Really.• Clearly we made some gross simplifications to the reality of

the situation• We did not use a Doppler radar• We assumed point sources rather than tumbling debris with a

time dependent radar cross section• We didn’t consider the plethora of fuel which is released during

the SRB separation…

• Even in making such simplifications, we didn’t get superb tracks

• We gained a first experience with gating and association, and the difficulties which come along with associating tracks

Conclusions• Tracking shuttle debris is an extremely important application

of modern radar tracking

• Different radars are used in viewing shuttle debris cross range as compared to down range

• It is rather simple to discuss and understand why gating and association is important, it is quite another to implement it.

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