(X-50LR) Program

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4. TITLE AND SUBTITLE

5a. CONTRACT NUMBER

An Overview of the Experimental 50-cm Laser Ramjet (X-50LR) Program (Postprint)

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) Franklin B. Mead, Jr., C. William Larson, and Sean D Knecht (AFRL/PRSP)

5d. PROJECT NUMBER 4847

5e. TASK NUMBER 0159

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

8. PERFORMING ORGANIZATION REPORT NUMBER

Air Force Research Laboratory (AFMC) AFRL/PRSP 10 E. Saturn Blvd. Edwards AFB CA 93524-7680

AFRL-PR-ED-VG-2005-394

9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)

Air Force Research Laboratory (AFMC)

AFRL/PRS 11. SPONSOR/MONITOR’S 5 Pollux Drive NUMBER(S) Edwards AFB CA 93524-70448 AFRL-PR-ED-VG-2005-394

12. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release; distribution unlimited

13. SUPPLEMENTARY NOTES Presented at the 4th International Symposium on Beamed Energy Propulsion, Nara, Japan, 11-14 Nov 2005.

14. ABSTRACT In January 2001, the X-50LR program was initiated to scale the Lightcraft concept ultimately to a 50-cm focal diameter, and to launch a 50 cm, fully functional vehicle, into space in either a sounding rocket or suborbital trajectory by the end of FY 2009. The current work involves scaling from a 10-cm aluminum Lightcraft to a composite 25-cm laser ramjet vehicle (X-25LR). An overview and status of this program will be given in terms of the various efforts that support this development. These efforts will include testing at the High Energy Laser System Test Facility (HELSTF), New Mexico; some results of the laser launch system study by Flight Unlimited; the development of silicon carbide materials for X-25LR parabolic reflectors by Trex Enterprises; supporting research by Air Force Office of Scientific Research (AFOSR); the different facets of attitude control in a small business program with Polaris Sensors Technology; continuing development of a launch model at The Pennsylvania State University; and, the development of a thrust measurement technique, and the use of a “mini-thruster” for research with The University of Alabama, Huntsville, in collaboration with the AFRL. This paper will be followed by a number of papers giving additional details of the efforts briefly overviewed in this presentation.

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19a. NAME OF RESPONSIBLE PERSON Dr. Franklin B. Mead, Jr.

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19b. TELEPHONE NUMBER (include area code) (661) 275-5929

Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. 239.18

An Overview of the Experimental 50-cm Laser Ramjet (X-50LR) Program

The 4th International Symposium on Beamed Energy Propulsion15-18 November 2005

Nara, Japan

Dr. Franklin B. Mead, Jr.,Dr. C. William Larson, andMr. Sean D. KnechtPropulsion DirectorateAir Force Research LaboratoryEdwards Air Force Base, CA

This briefing is distribution A: Approved for public release, distribution unlimited

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Presentation Outline• The Lightcraft Concept

• The Experimental 50-cm Laser Ramjet (X-50LR) ProgramObjectives, Critical Technologies, and Payoffs

Current Program Collaborations And Technical Contributions– Testing at HELSTF

X-25LR

10-cm Lightcraft

Mini-thruster research

– AFOSR Programs and Support

High Isp Propellants

– Attitude Control (Phase II SBIR)

Thermal Structural Analysis of Parabolic Plug Nozzle

Adjustable Pivot Point Pendulum

– Some Launch Code Results

• Summary This page is Distribution A: Approved for public release, distribution unlimited

3

The Lightcraft ConceptThe Lightcraft Concept

• A Lightcraft is a small spacecraft; diameter is ≤1.0 m, weight is ≤ 8.0 kg (≤2.0 kg payload)Forebody

Aerodynamically contoured surfaceAnalogous to rocket payload bay; opens in space to release payload and expose solar cells

ShroudCentrally located “belt”Analogous to rocket combustion chamber; ejected plasma provides thrust

AfterbodyAnalogous to rocket nozzle; parabolic mirror and plug nozzle

RecentAFRL Test

VehicleThis page is Distribution A: Approved for public release, distribution unlimited

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AFRL/PRS Program ForAFRL/PRS Program ForLaser Propulsion DevelopmentLaser Propulsion Development

• ObjectivesEliminate remaining major technical hurdles for a laser launch vehicle• Critical Technologies

– Airframe & Structure - Materials– Ablative energetic propellants– Theoretical modeling and flight simulation– Electronic Systems– Chemical Propulsion

Conduct a high altitude flight demonstration using the technology developed under this program• Using PLVTS CO2 laser upgraded in power by factor

of 2 or 3• Payoffs

Provide a paradigm shift for space access• Entirely different infrastructure

– No huge motorized tractors for moving vehicles– No skyscraper gantries– No standing army of mechanics & technicians– No toxic fuels– No significant explosive hazards– No large propellant farms

Low cost access to space for nano-satellites

25 cm Laboratory Model

This page is Distribution A: Approved for public release, distribution unlimited

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Attitude ControlPolaris Sensors Techn.

Mr. John Harchanko

Ablation of Solid FuelsInst. of Technical Phys.

Mr. Wolfgang Schall

X – 50LRDr. Franklin Mead, Jr.

AFRL/PRSP

Current Program CollaborationsCurrent Program Collaborations

Ablation of Liquid FuelsTokyo Inst. of Technology

Dr. Shigeaki Uchida

Laser LaunchersAFOSR MURI/SBIR/STTR

Dr. Mitat Birkan

CO2 Laser: Lab & Flight TestingHELSTF/WSMR

Mr. Steve Squires

= Government Agencies= Contractors= Foreign Research

Computer Launch ModelU. Washington (Co-Op)

Mr. Sean Knecht

Mini-Thruster ResearchU. Alabama, HuntsvilleDr. Andrew Pakhomov


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Pulsed Laser Vulnerability Test System(PLVTS)

Original Performance• 1,000 joules/pulse • 10 Hz• 30 μsec pulses

Modified Performance• 1998

400 joules/pulse25 Hz18 μsec pulses

• 1999150 joules/pulse30 Hz5 μsec pulses

Proposed Performance• 1,500 joules/pulse• 20 to 35 Hz• 25 μs pulses

The PLVTS has powered the AFRL laser The PLVTS has powered the AFRL laser propulsion test and evaluation programpropulsion test and evaluation program


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Frank Mead, Bill Larson, Sean Knecht, AFRL/PRSPJim Shryne, RSI (Photographer)John Harchanko, POLARIS TECHNOLOGIESSteve Squires, Chris Beairsto, Mike Thurston, &Jay Spray, WSMR/HELSTF/PLVTS

Team December 2004Pulsed Laser Vulnerability Test System


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Mettler Balance or Digital Balance

Measure mass to + 0.3 mg


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• X-25LR Bench ModelFabricated by COI Ceramics

Amorphous SiNC MatrixReinforced with Nicalon fiberRecommended up to 1473º K

Tested With Delrin®

COI Nicalon parabolas gave poor performance– Fibers coated with Cu yielded poor,

inaccurate mirror qualityRequired Al parabola with mirror finish– Performance Excellent

• Shadowgraph Tests in Air10-cm Aluminum Lightcraft Laboratory Model18 μs and 300 JExit plane traverse = 10 μs

Laboratory Tests at HELSTF

X-25LR Test with Black Delrin®

10-cm Lightcraft Shadowgraph Testat 45 μsThis page is Distribution A: Approved for public release, distribution unlimited

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Lightcraft and Mini-Nozzle Standard

200-3/4 Lightcraft (10-cm) Mini-Thruster26o divergence angle

ε = 8 ε = 16

Delrin0.64 g

ε (ideal plug nozzle) = 14M = 40g

Delrin surface area ~ 25 cm2

350 J/25 cm2/18 μs = 0.8 MW/cm2

Cm = 450 N/MW, EL/m = 5.1 MJ/kgVe = 2270 m/s, efficiency = 0.51

T/W = Cm·P/mg = 11 at P=10 kW

ParabolicOptic

Focus

Shroud

Fore body

10g Delrin

ε = 8M = 7.8 g

Delrin surface area ~ 0.71 cm2

25 J/0.71 cm2/18 μs = 2.0 MW/cm2

Cm = 442 N/MW, EL/m = 6.3 MJ/kgVe = 2795, efficiency = 0.62

5 cm

5 cm


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Mini-Thruster 25 J, 18 μs, 0.71 cm2


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I, m, EL for Mini-Thruster

Miniature Nozzle w ith black or w hite Delrin

I = 0.000444 ELR2 = 0.97

I = 0.000439 ELR2 = 0.98

I = 0.000253 ELR2 = 0.97

0.000

0.005

0.010

0.015

0 5 10 15 20 25 30laser energy (J)

Impu

lse

(Ns)

w hite

black

air

Miniature Nozzle w ith black or w hite Delrin

m = 0.000160 ELR2 = 0.99

m = 0.000156 ELR2 = 0.98

0

0.001

0.002

0.003

0.004

0.005

0 5 10 15 20 25 30laser energy (J)

mas

s ab

late

d (g

)

w hite

black

I/EL = 444 Ns/MJ m/EL = 0.160 mg/JVe = (I/EL)/(m/EL) = 2775 m/s = 283 s of Isp

Efficiency = ½(I/EL)2/(m/EL) = 0.616 = αβΦ∗


Miniature Nozzle with black or white Delrin

* See: Larson et al., AIAA 2002-0632, 2002

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10 cm Light Craft 322 J, 18 μs


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I, m, EL for Lightcraft 200-3/4 (10-cm)

10 cm w hite and black Delrin

I = 0.000447 ELR2 = 0.85

I = 0.000453 ELR2 = 0.92

0

0.05

0.1

0.15

0.2

0 100 200 300 400EL (J)

Impu

lse

(Ns)

black

w hite

I/EL = 447 Ns/MJ m/EL = 0.201 mg/JVe = (I/EL)/(m/EL) = 2224 m/s

Efficiency = ½(I/EL)2/(m/EL) = 0.497 = αβΦ

10 cm w hite and black Delrin

m = 0.000194 ELR2 = 0.93

m = 0.000201 ELR2 = 0.96

0.0000

0.0100

0.0200

0.0300

0.0400

0.0500

0.0600

0.0700

0 100 200 300 400EL (J)

Abla

ted

mas

s (g

)

black

w hite


10 cm white and black Delrin 10 cm white and black Delrin

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Conclusions/Work in Progress

• Cm= 450 N/MW for Lightcraft with Delrin® (350 J, 18 μs)

• Cm= 442 N/MW for mini-thruster with Delrin® (25 J, 18 μs)

• 51 % efficiency for EL to jet KE for Lightcraft

• 62 % efficiency for EL to jet KE for mini-thruster

• Future experiments

– Vary pulse width, 5 and 30 μs, expansion ratio, ε = 4, 16, …

– Increase EL up to ~ 100 J/pulse in mini-thruster

– Measure time resolved thrust with piezoelectric sensor

– Develop chemically enhanced ablative propellants

• Future calculations with chemical equilibrium applications code

– Factor pressure thrust into analysis

– Analyze chemically energetic propellants*


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0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 11000

exit v elocity v E = I/m (m/s)

0

100

200

300

400

500

600

700

800

900

1000

Cou

plin

g co

effi

cien

t C

m =

I/E

L N

s/M

J

AirBD27a.axg July 23, 2002 11:42:54 AM

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

0.2

0.1 α β Φ

Phipps (proprietary)

1.00.90.80.7

0.60.5

0.40.3

0.2

α β Φ

equilibrium

Phipps and Luke (2002) Black PVC

pryoxlyn

DLR Delrin PVC (PET) 44*

(PET)

2 M

J/kg

PVC (PET) 46*

Printer's ink

com pared to equilibrium ande fficie ncy for several solid prope llantsα β Φ

frozen blow dow n of air to 1 bar

0.1

6 MJ/k

g

10 MJ/kg

40 MJ/kg

frozen

air blowdown

1 M

J/kg

3 M

J/kg

4 M

J/kg

5 M

J/kg

AFRL Delr

in

7 MJ/k

g

9 MJ/k

g

15 MJ/kg

20 MJ/kg

30 MJ/kg

Φ = 8/3π = 0.849Maxwellian gas

8 MJ/k

g = (u c

- uo ) /

= E L

/m

β

50 MJ/kg

air blowdownfrozen equil ibrium

Performance Map of Known Laser Propellants

60 MJ/kg


ResearchPropellants

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Thermal Structural Analysis(Laser Lightcraft Thin-Walled Aluminum Plug Nozzle)

• Performed by SYColmanDirected by Polaris Sensor Technologies

Under SBIR Phase II contract for attitude control

• Desire to predict deformed shape of parabola as a function of time and input power

Based on initial geometry and varying temperature

• Results from modelMaximum displacement increases linearly with temperature

Significant optical degradation and distortion of reflected beam with predicted beam surface deformations

COI Nicalon material showed little or no resultant deformation ≤ 1,000º F

Full Power, Multi-Pulse Laser Heating of Flight-weight Lightcraft Parabola with Shroud Attached


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• Improved technique Pendulum is brought into balance by adjusting its pivot-point

Coincide with Lightcraft/pendulum’s combined center of gravity

More sensitive than standard pendulum

Developed for measuring side/restoring forces

Gantry size determines range of test articles that can be handled*

Impulse Pendulum with Adjustable Pivot Point

SchaevitzRVDT

PiezotronicsCalibrationHammer 10-cm

LaboratoryLightcraft

Gantry


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X-25LR Space Launch Simulation

• Pulsed CO2 laser1 MW1,000 joules/pulse30 Hz25 μs pulses

• Vehicle parameters for simulations25 cm diameter, Dry mass (structure) = 0.21 kg Payload = 0.21 kg Propellant (mass fraction = ½) = 0.42 kg Total mass = 0.84 kg (1.85 lbs)


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Results: 1 MW 10.6 μm Laser

Altitude vs. Time of Flight

0.00

50.00

100.00

150.00

200.00

250.00

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00

Time (s)

Alti

tude

(km

)

Airb

reat

hing

Ter

min

ates

Roc

ket T

erm

inat

es


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Mach Number vs. Time of Flight

0.005.00

10.0015.0020.0025.0030.0035.00

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00

Time (s)

Mac

h Nu

mbe

r

Airb

reat

hing

Ter

min

ates

Roc

ket T

erm

inat

es


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Range from Laser vs. Time of Flight

0.00E+00

5.00E+02

1.00E+03

1.50E+03

2.00E+03

2.50E+03

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00

Time (s)

Ran

ge (k

m)

Airb

reat

hing

Ter

min

ates

Roc

ket T

erm

inat

es


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• AFRL laser propulsion ready for advanced development (6.3) with a quarter scale vehicle

Composite, airbreathing, 25-cm vehicle needs additional developmentHigh altitude flights are possible using active ACS on a 25-cm laser propelled vehicle

• Critical technologies required to be ready for engineering development (6.4)

Airframe & Structure – MaterialsAblative energetic propellantsTheoretical modeling and flight simulationGuidance, Control, Power, & SensorsChemical Propulsion

• Operational status could be reached within 3 to 4 yearsA MW class laser will be requiredThe major technologies required for laser propulsion will need to be demonstrated under an advanced development program

• A rather modest investment to achieve a means for a new, unique, low-cost access to space

Laser Propulsion technology has the potential to make low-cost access to space a reality in the near future

Taking us from here …

… To there!


XX--50LR Program Summary50LR Program Summary

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The End


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