Optimizing the Delta-V Capability of a CubeSat Mission with Novel

BravoSat:

Optimizing the Delta-V Capability of a CubeSat Mission

with Novel Plasma Propulsion Technology

Themis Ground Stations Image Credit: nasa.gov Website

:, NASA (satellite constellation in measuring the Aurora Borealis over North America. Each ground station has an all-sky imaging white-light auroral camera and a magnetometer. The ground stations' radial coverage is rendered at 540km.)

Image Credit: Allison Craddock

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Sara Spangelo, NASA JPL, Caltech

Benjamin Longmier, University of Michigan

Interplanetary Small Satellite Conference, June 2013

Magnetic Field lines

BravoSat Orbit

How Far Can CubeSats Go (Alone)?

• Can CubeSats go beyond Low Earth Orbit (LEO)?

• Is there a fundamental size, mass, power, cost limitation? No!

• BravoSat: CubeSat with CAT engine designed to escape Earth orbit

• Enabling factors:

1. Miniaturized thruster technology with high ∆V capabilities

2. Heritage and experience operating CubeSats in LEO

3. Intelligent use of mass/ volume/ energy!

Photo Credit: NASA Website

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Is the Sky the Limit? Dream versus Reality

Image Credit: CubeSat Team Websites, Survey: http://gs.engin.umich.edu/sat_survey/

Dream (Goal):

• Can we escape Earth orbit? How far can we go?

• Maximize altitude increase on a CubeSat….. [Not equal to maximizing ∆ V]

Reality (Constraints)

• Maximum engine power (thrust)

• Initial orbital configuration (LEO)

• CubeSat or small satellite:

• Physical (mass/ volume)

• Limited potential to collect/ store energy

• Lifetime- degradation of batteries, solar panels, radiation, etc.

CubeSat Missions

From Small Satellite Survey

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

https://ums.jpl.nasa.gov/owa/redir.aspx?C=DfCsy0g4P0-kNsDezCjz4M3yAyNAPtAIMH5R2wtTjmOGi0mBnO_0uQs3RhmQEiEUUrrgL7OiKIc.&URL=http%3a%2f%2fgs.engin.umich.edu%2fsat_survey%2f

How Much ∆V Is Needed?

Image Credit: Google Images

Starting in LEO, escaping Earth’s Sphere of Influence (SOI): ∆V~ 7km/sec

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Distance from Earth (Altitude), km

Vel

oci

ty, km

/sec

Maximum

LEOGEO

Closest Mars

Approach

Moon

Orbit

Earth

SOI

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Transferring from circular orbit to circular orbit

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

CAT: Large ∆V Engine Capability

CAT: CubeSat Ambipolar Thruster

• Uses high-density plasma source

• Achieves high ∆V and high thrust/power

• Fits within small spacecraft form-factor

• Many small satellites communicate only to one or a handful of

dedicated ground stations.

• Existing ground stations are monolithic in design and largely underutilized.

Design of a 5 kg 3U CubeSat with CAT engine

performing initial testing in Low Earth Orbit. Photo Credit: PEPL

Feel free to update

(amazing matching of color schemes!)

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Linear relationship:

Mass flow ∝ power

Used to select best trade-off between thrust, ηthruster, and Isp

CAT: Large ∆V Engine Specifications

Fixed peak electron temperature Te.max 30 eV

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Is this Really Feasible for a CubeSat?

Helios, http://www.fripro.com/dryden_helios_1024.jpeg

Image Credit: PEPL

Internet-enabled communication system where

ground

stations are independently owned +

loosely cooperative

Growing with ElaNa

launches (33 in 2013-4) and

constellation missions

Photo Credit: Nunuk Photos

Let’s review the major constraints:

1. Mass/ Volume

⇾ CAT Engine is <.5U, <.5 kg

⇾ Fuel ~2.5 kg required (~.5 U)

⇾ Total: ~3kg, 1U, Remaining: 2kg, 2U1

2. Instantaneous Power

⇾ Thruster can operate up to 100W, supportable by custom CubeSat bus

3. Energy and Time

⇾ Trade between power * time (thruster is on) and available energy

⇾ Constraint on mission duration!

Summary: None of these constraints are show-stoppers for a CubeSat!

Launch Statistics Credit (1990-2010): Sigfried Janson, The Aerospace Corp. [1] Baker et al., 2008, [2] Moretto et al., 2008, [3] Buck et al., 2012, [4] Ridley et al., 2010, [5] Cutler et al., 2006 The quartz plasma liner supported by plastic stand.

CAT engine with CubeSat subsystems

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

1 Assuming 5kg 3U CubeSat

How Much Mass Is Needed?

g: gravity constant = 9.81 m/sec2

We can escape Earth’s Sphere of Influence (∆V~ 7km/sec) with ~2.5 kg of fuel!

Ideal Rocket Equation

Parameter Symbol Input/ Equation Value Units

Specific Impulse Input 1010 sec

Exhaust Velocity 9908 km/sec

Dry Spacecraft Mass Input 2.5 kg

Propellant Mass Input 2.5 kg

Initial Mass 5.0 kg

Final Mass 2.5 kg

Delta V Capability 7.0 km/sec

CAT Thruster, I2 Fuel

Work through Rocket Equation for I2 fuel and CAT

Add flow rates, Isps for I2 fuel *Reasonable based on typical CubeSat designs (backup slide?)

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

How Much Mass Is Needed?

We may be able to escape with even <2.5 kg fuel!

Parameter Units

Destination

Maximum

LEO GEO

Mean

Moon

Earth's

SOI

Closest Mars

Approach

Distance from

Earth km 2,000 35,700 384,000 925,000 56,000,000

∆V km/ sec 0.6 4.4 6.5 6.9 7.4

I2 Fuel kg 0.3 1.8 2.4 2.5 2.6

Ga Fuel kg 0.2 1.4 1.9 2.0 2.1

H20 Fuel kg 0.1 0.8 1.1 1.1 1.2

Let’s review different fuels and destinations

Add flow rates, Isps for all fuels

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Vel

oci

ty, km

/sec

Maximum

LEOGEO

Closest Mars

Approach

Moon

Orbit

Earth

SOI

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

LEO: Low Earth Orbit, GEO: Geostationary Earth Orbit, SOI: Sphere of Influence

How Much Time Is Needed?

LEO: Low Earth Orbit, GEO: Geostationary Earth Orbit, SOI: Sphere of Influence

We can escape Earth’s Sphere of Influence in < 1 year!

Parameter Units

Destination

Maximum

LEO GEO

Mean

Moon

Earth's

SOI

Closest Mars

Approach

Distance from

Earth km 2,000 35,700 384,000 925,000 56,000,000

∆V km/ sec 0.6 4.4 6.5 6.9 7.4

I2 Fuel days 32 194 259 269 284

Ga Fuel days 36 226 308 321 341

H20 Fuel days 202 1,369 1,933 2,026 2,171

Constant thrust at 10 Watts

Let’s review different fuels and destinations

Note time is proportional to power because mass flow rate is linear with power!

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Vel

oci

ty, km

/sec

Maximum

LEOGEO

Closest Mars

Approach

Moon

Orbit

Earth

SOI

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Three Strategies for Trajectory Design

Case

# Description Consider

Energy?

Consider

Magnetics?

Exploit

Perigee?

1 Constant thrust along

velocity vector

100W: No

10/20W: Yes

No No

2 Phase 1: Thrust when

α<30 Phase 2: Pulse

thrust every 200 minutes

Yes Somewhat No

3 Thrust at perigee along

velocity vector2

Yes Yes Yes

and also thrust at apogee if perigee threatens to

crash into the Earth

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

1 α: Angle between the velocity vector and thrust vector (aligned with Earth’s magnetic field for passively stabilized craft) 2 Assume perigee is roughly when α is small

1-3: Consider additional realistic constraints and exploit environmental factors

Case 1: Constant Thrust Along Velocity Vector


BravoSat Orbit

Exhaust Vector

Velocity Vector

Thrust Vector

Work through Rocket Equation for I2 fuel and CAT

*Not to scale

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BravoSat Orbit

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions


BravoSat Orbit

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2.5 kg fuel, 2.5 kg dry mass Initial 700 km circular orbit

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Add specs for this example

Starting altitude

Escape Earth’s Sphere

of Influence (SOI)

requires ~2.5 kg

Earth’s Sphere of Influence (SOI)

Requires ~2.5 kg!

Starting in 700km circular polar orbit with 2.5 kg dry mass

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How much mass do we need?

Depends how far you want to go!!!


ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Results are shown when all fuel is used


BravoSat Orbit

Exploiting CAT’s Magnetic Dipole

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Body Axis Definition

Velocity Vector

Thrust Vector

*Strongest Sinclair Interplanetary torque rods ~ 48 Am2!

Body Z axis

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions


BravoSat Orbit


BravoSat Orbit

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Passive Magnetic Stabilization Scheme

Velocity Vector


ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions


BravoSat Orbit

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Desirable Configuration for Thrusting to Exploiting Passive Magnetic Stabilization

Velocity Vector

Thrust Vector

BravoSat Orbit

Body Z axis

Velocity Vector


α

Body Z axis

Velocity Vector

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Include Sim specs in STK

Short, high-powered (100W) burns

Example: Thrust only when α1 < 40o

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Body Z axis

Velocity Vector

α

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Include Sim specs in STK

Challenge: Once orbit grows, must be smarter about thrust duration (energy, thermal)

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Short, high-powered (100W) burns

Strategy:

1. Phase 1: Thrust for 10 minutes when velocity and thrust vectors aligned

2. Phase 2: Thrust for 10 minutes every 200 minutes (pulsing)

Rationale:

• Exploit passive magnetic stabilization in Phase 1

• Thrust at perigee, where thrust vector ~parallel to velocity vector

• Energetically possible in both phases (thrust <10 minutes at a time)

Case 2: Multi-Staged Approach

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions


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Phase 1: Thrust <10 mins when aligned

Phase 2: Thrust every 200 mins for 10 mins

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Results sampled once a day

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Initial Fuel

Mass

Time to run out of fuel Radius when out of fuel

2 kg 320 days 1.39 ·106 km

2.5 kg 389 days 4.95 ·106 km


You could also stop thrusting when achieve desired radius and use remaining fuel for later fun!

Starting in 700km circular polar orbit with 2.5 kg dry mass

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Total ∆V when ran

out of fuel

5.8 km/ sec

6.9 km/ sec

Case 3: Exploiting Perigee to Escape Earth!

Strategy:

1. Start in elliptical orbit (assume 500km x 1500km)

2. Thrust at perigee (100W, 10mins), when α small

3. Continue until escape Earth orbit, or run out of fuel/time

Rationale:

• Exploit passive magnetic stabilization

• Energetically feasible (thrust once per orbit for 10 mins)

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Escaping with 1 kg fuel!


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Possible if apogee is between L1 and L5 or between L3 and L4

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Interesting variations due to Earth-Moon interactions until escapes!


Note results are sampled once a day


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Starting in 500km x 1500km orbit with 2.5 kg dry mass

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Magnetic field still high at perigee

So can use passive stabilization

Interesting interactions with the Moon!


Note results are sampled once a day

Something about magnet

Strength!!!

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Starting in 500km x 1500km orbit with 2.5 kg dry mass

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Consider 3 Different Approaches: Summary

# Description Power Fuel to

Escape

Time to

Escape

Challenges

1 Constant thrust

along velocity vector

10 W Constantly 2.5 kg 269 days Require attitude control

20 W Constantly 135 days

2 Phase 1: Thrust

when α1<30

Phase 2: Pulse thrust

every 200 minutes

100 W/

>1,000 times

2 kg 320 days Require attitude control

High number of battery

cycles

3 Thrust at perigee

along velocity

vector2

100 W/

~700 times

~1 kg < 3 years Require initial elliptical

orbit

Require (fine) active

attitude control

and also thrust at apogee if perigee threatens to

crash into the Earth

Disclaimer: These are not optimized, but rather representative results!

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1 α: Angle between the velocity vector and thrust vector (aligned with Earth’s magnetic field for passively stabilized craft) 2 Assume perigee is roughly when α is small

Best-case results assuming firing with 2.5 kg dry mass

ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Conclusions/ Future Work


Problem:

• Growing small satellite community face many challenges

• Downloading large amounts of data limited by ground station infrastructure

• Spacecraft constrained by power, size, mass, cost, risk

Image Credit: TurksatVSAT Website


ground


loosely cooperative

Growing with ElaNa




Radio Aurora eXplorer (RAX) CubeSat

Conclusions

• Demonstrated feasibility of CubeSat (CAT engine) to escape Earth orbit!

• Explored 3 “firing” strategies to:

• Minimize fuel mass, firing time, time to escape Earth orbit

• Consider realistic constraints/ environmental factors

Future Design Considerations

• Battery degradation, radiation (South Atlantic Anomaly, Van Allen Belts)1

Future Work

• Refining strategies, optimizing to minimize fuel mass/ power/ time

• Identifying design factors for CAT development (e.g. thermal, power, magnetic)

1May be able to overcome these challenges with adequate radiation shielding (e.g. <1MeV Al shielding)




RAX-1, the first NSF funded 3U nanosatellite and built by MXL

30 cm

10 cm

Launch Statistics Credit (1990-2010): Sigfried Janson, The Aerospace Corp. [1] Baker et al., 2008, [2] Moretto et al., 2008, [3] Buck et al., 2012, [4] Ridley et al., 2010, [5] Cutler et al., 2006

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ISSC 2013

Motivation

Problem

CAT Engine

Feasibility

Strategies

Conclusions

Acknowledgements


Problem:

• Growing small satellite community face many challenges

• Downloading large amounts of data limited by ground station infrastructure

• Spacecraft constrained by power, size, mass, cost, risk

Image Credit: TurksatVSAT Website


ground


loosely cooperative

Growing with ElaNa




Radio Aurora eXplorer (RAX) CubeSat

• JP Sheehan, University of Michigan

• PEPL Members, University of Michigan

• Derek Dalle, University of Michigan

• James Smith, Jet Propulsion Lab




RAX-1, the first NSF funded 3U nanosatellite and built by MXL

30 cm

10 cm

Launch Statistics Credit (1990-2010): Sigfried Janson, The Aerospace Corp. [1] Baker et al., 2008, [2] Moretto et al., 2008, [3] Buck et al., 2012, [4] Ridley et al., 2010, [5] Cutler et al., 2006

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Questions?


BravoSat Orbit Magnetic Field lines expanded on side opposite to the Sun

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Optimizing the Delta-V Capability of a CubeSat Mission with Novel

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