Propellant estimation by Thermal Gauging Method (TGM) Dr Boris - - PowerPoint PPT Presentation

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Propellant estimation by Thermal Gauging Method (TGM) Dr Boris - - PowerPoint PPT Presentation

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Propellant estimation by Thermal Gauging Method (TGM) Dr Boris Yendler YSPM Agenda Introduction How Thermal Gauging Method (TGM) can help satellite operator How YSPM can help satellite manufacturer to make satellite TGM

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Propellant estimation by Thermal Gauging Method (TGM)

Dr Boris Yendler

YSPM

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SLIDE 2

Agenda

  • Introduction
  • How Thermal Gauging Method (TGM) can help satellite operator
  • How YSPM can help satellite manufacturer to make satellite TGM

“friendly”

  • Basic of Thermal Gauging Method (TGM)
  • Requirements for using TGM
  • Comparison with book-keeping and PVT
  • Example of TGM estimation
  • Looking back

– Past performance – Awards – Testimonial

  • Conclusion
  • References

2

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How TGM will help Satellite Operator

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SLIDE 4

Benefits to Operator

  • More accurate estimation of propellant

remaining – TGM is more accurate than book-keeping and PVT at EOL

  • TGM is independent method – book-keeping (BK)

and PVT methods are NOT independent (both use pressure transducer)

  • Increase confidence in accurate determination
  • f EOL – use of independent methods increase reliability of

estimation (BK and PVT methods are NOT independent)

  • TGM helps an Operator to make accurate

business decision

4

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SLIDE 5

How YSPM helps Satellite Manufacturer

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SLIDE 6

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Designing Satellite being TGM “friendly”

YSPM will work with satellite manufacturer to make satellite TGM “friendly” on design stage. We will help to determine an optimal designs of:

  • Heater

– Position on a tank – Shape – Ground control – Power

  • Temperature sensor

– Position on a tank – Accuracy – Telemetry A/D and D/A conversion

  • Tank thermal connection:

– To s/c environment, e.g., optical properties of MLI, panels, etc – Between tanks (multi-tank system)

  • Allowable temperature rise
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SLIDE 7

Thermal Gauging Method Basic

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Basics

  • Temperature rise can be induced by: Tank heaters; Sun load;

Equipment (e.g. IRU unit on BSS 601); etc.

  • Thermal Gauging Method (TGM) accuracy improves with load

propellant load decrease because sensitivity of temperature rise to tank load is increasing when tank load drops

  • The method is capable of gauging:
  • individual tanks in multi-tank propulsion systems with no

separation valve

  • Mono and bi propellant propulsion systems

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Measure a propellant tank load using temperature rise

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SLIDE 9

TGM Phases

  • 1. Build integrated Thermal Model (Tank(s) and Spacecraft)
  • 2. Prepare and Conduct in-flight test (tanks heating and cooling)
  • 3. Calibrate integrated model per flight conditions
  • 4. Find propellant load of each tank
  • 5. Determine accuracy of the estimation

Regardless of spacecraft type, Thermal Gauging method follows the same phases

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Requirements for estimation

  • Spacecraft design – to build Tank and Spacecraft Thermal

Models

  • Tank temperature – typically propellant tanks have

thermistors

  • A mean of changing tank temperature – heater

(tank, bus unit, payload, etc), sun NOT MUCH

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Comparison with other Propellant Gauging Methods

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Methods of Gauging

  • Bookkeeping- calculate consumed propellant (includes ∆V,

ranging, etc)

– Accuracy worse over time due to accumulation of error

  • Pressure, Volume, Temperature (PVT) - calculate

remaining propellant based on Gas Law (including variants

like re-pressurization)

− Accuracy worse over time due to lost of sensitivity of He pressure to volume change in tanks with low propellant load

  • Thermal Methods - calculate remaining propellant based
  • n temperature rise (Including ESA TPGS, Comsat PGS, TGM, …)

+ Accuracy better over time

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Bookkeeping vs. Thermal Gauging Method

  • Bookkeeping accuracy is calculated based on consumed fuel

Assuming accuracy of 2% ; uncertainty – 450 kg x 2% = 9 kg

  • TGM accuracy is calculated based on remaining fuel

Assuming accuracy – 12%; uncertainty – 50kg x 12% = 6 kg

450 kg consumed 50 kg remaining Tank Initial Load = 500 kg

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PVT vs. TGM at BOL

Beginning of Mission (BOL) PVT

– gas volume 1 liter; using 1 liter of propellant doubles gas volume- pressure reduces 50% – 2% accuracy of gas volume is 0.2 liter – (≈ 0.2 kg) – Propellant load 499 kg; using 1 kg of propellant reduces mass by 0.5%; small change in slope of temperature rise – 12% accuracy is 60 kg

Thermal

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Assuming: propellant tank ≈500 liter; accuracy of PVT – 2%; TGM – 12%

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PVT vs. TGM at EOL

– gas volume 480 liters; using 1 liter of propellant increases He volume by 0.2%- pressure reduces 0.2% – 2% accuracy of gas volume is 9.6 liters (≈ 9.6 kg) – Propellant load 20 kg; using 1 kg reduces mass by 5%; significant change in thermal response – 12% accuracy is 2.4 kg

PVT Thermal

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Comparison (example of generic spacecraft)

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  • Book-keeping, PVT

– High accuracy at Beginning of Life (BOL) through Middle of Life (MOL) – Low accuracy at End of Life (EOL)

  • Thermal Gauging

– High accuracy towards EOL

End Beginning

Accuracy

High Low

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SLIDE 17

Example of TGM Extimation

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Step 1a-Tank High Fidelity Model

  • 3-D propellant distribution in the tank using

Surface Evolver

  • Grid for Finite Element Model (FEM)

− high enough density to simulate temperature gradients

  • More then 20000 nodes
  • Detailed propellant and temperature distribution
  • Simulation run time (6 – 10 hours per run)
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SLIDE 19

Tank High Fidelity Model-cont’d

Tank Model Temperature Distribution (heaters are on domes)

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Step 1b - Satellite Models

StarDust (Ref.4) SpaceBus 2000 (Ref.2) BSS 601 (Ref.1) EuroStar 2000 (Ref.3)

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East West East West

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Step 2a- Test Procedure

  • Avoid eclipse season (change of thermal condition)
  • No change in payload/Bus unit configuration

(change of thermal condition)

  • No station-keeping maneuvers performed (change
  • f propellant load, sloshing)
  • Enough time to cool-down for the tanks after

turning heaters OFF

  • Tank temperature can not exceed qualification limit

Operational Constrains Get approval from Manufacturer before the test

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Step 2b- in-flight test

Heaters ON

(Fig.4 from Ref.2 )

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Step 3 - S/C Model Calibration

  • No ground calibration is required
  • Calibration is performed using current flight data
  • Calibration of satellite model to reflect current

condition of the satellite

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Step 4 -Propellant Estimation

Flight vs Simulation

Lines – simulation results; Markers – Temperature Sensor reading Tank heaters were turned ON at t=0 (Fig.5 from Ref.2)

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Error Analysis – Step 5

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Categories of Uncertainty

Two categories of uncertainty

  • A least squares curve fit and associated

uncertainty

  • Uncertainties of specific model parameters

– Physical parameters – Temperature measurement – Numerical model

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Error Analysis Starting Point

  • Satellite data:

(Ti, ti)

  • Simulation curves:

T(t, m, p1, p2, p3,…, q1, q2, q3,…)

  • Uncertainties for q parameters:

σqi

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Least Squares Analysis

[ ]

∑

− =

i i i

q q p p m t T T M

2 2 1 2 1

,...) , ,..., , , , (

28 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 1 2 3 4 5 6 7 8 9 10 11 12 Mismatch Function Load [kg]

(Fig. 4 from Ref.4) Load is determined by Minimizing function M with respect to propellant mass Mismatch Function M

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Uncertainty

  • Assuming that the model is a good fit apart from

statistical errors,

  • These can all be calculated. The variance of Ti comes
  • ut of the least squares fit if we assume they are all

equal.

2 2 2 2 2

j

q j j T i i m

q m T m σ σ σ

∑ ∑

        ∂ ∂ +         ∂ ∂ =

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TGM Accuracy of Estimation

Bottom Line

  • Theoretical accuracy is determined by uncertainty

analysis (Phase 5)

  • Theoretical uncertainty is conservative
  • Actual accuracy can be determined ONLY after

tank(s) depletion

  • Existing flight data indicate that Actual accuracy of

Thermal Gauging Method is about 12% - 15% of propellant remaining

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Typical Schedule of TGM estimation

  • paper w ork SOW, NDA, Contract

– 3 weeks

  • Model development

– 2 weeks

  • In-flight test

– 2 weeks

  • Model Calibration

– 2 weeks

  • Propellant Estimation

– 2 weeks

  • Uncertainty Analysis

– 1 week

  • Final Report

Total – 12 weeks

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Typical Deliverables

  • One summary report with test procedure
  • One summary report with propellant estimation
  • One summary with accuracy of estimation
  • One final report

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SLIDE 33

Looking Back

  • Past Performance
  • Awards
  • Testimonials
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Past Performance - S/C Platforms

  • My experience includes more than 45 thermal gauging

estimations during last 7 years including the following platforms: – Alcatel/TAS France SpaceBus 2000, 3000A – Astrium/EADS EuroStar 2000 – Boeing SS 376, 601 – LM A2100, Ax2100, series 3000, 5000,7000 – US Government – SS/Loral FS1300 – NASA (StarDust)

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S/C Platforms – cont’

  • Majority of spacecrafts have tank heaters and thermistors
  • Thermal gauging has being successfully used on spacecrafts not

designed specially for the approach, like StarDust, SS/L FS1300, SpaceBus 2000, etc

  • Thermal gauging was even successfully used for BSS 601 which

does not have tank heaters

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Customers and Awards

My customers include but not limited to : USA (Loral Skynet); US Government (USAF, NASA); Japan SkyPerfect (JSAT, SCC); Turkey (Turksat); France (Thales); Canada (Telesat), Saudi Arabia (Arabsat); etc.

COMSAT PGS group received 2006 US Air Force Chief of Staff Team Excellence Award

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SLIDE 37

"The DSCS program office's satellite life extension efforts help to save up to five million dollars per year," said Brig Gen Ellen Pawlikowski, MILSATCOM Systems Wing Commander. "By extending the life of the DSCS constellation and by sharing these innovative techniques with other space programs, the team's work will be felt for many years to come.“ Astro News, November 3, 2007 www.aerotechnews.com

Testimony from USAF

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Conclusion

  • Thermal Gauging Method w ill provide accurate

propellant estimation for satellites of different platforms

  • Thermal Gauging Method provides independent

estimation of propellant remaining

  • Use of the TGM increase reliability of the

estimation

  • TGM helps operators to make accurate business

decision

  • YSPM w ill help manufacturers to design

spacecraft “thermal gauging friendly”

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References

1.

  • T. Narita, B. Yendler, "Thermal Propellant Gauging System for BSS 601", 25th

AIAA International Communications Satellite Systems Conference (organized by APSCC), September 18–20, 2007, Bangkok, Thailand, paper AIAA 2007- 3149 2. B.Yendler, et all, "Thermal Propellant Gauging, SpaceBus 2000 (Turksat 1C) Implementation", AIAA SPACE 2008 Conference & Exposition, September 9– 11, 2008, San Diego, California, paper AIAA 2008-7697 3. Apracio, B.Yendler,"Thermal Propellant Gauging at EOL, Telstar 11 Implementation", Space Operations 2008 Conference, May 12–16, 2008, Heidelberg, Germany, paper 2008-3375 4.

  • B. Yendler, et all, "Fuel Estimation for StarDust NExT mission",

AIAA Space 2010 Conference and Exposition, Aug 30–Sep 2, 2010, Anaheim, CA, USA

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