A Multiprobe Flagship Mission to Explore Ice Giant Uranus

Kunio Sayanagi, Principal Investigator

Hampton University

Robert A. Dillman, Chief Engineer

NASA Langley Research Center

NASA Planetary Science Deep Space SmallSat Studies

March 18, 2018
1

Study Team

Kunio M. Sayanagi (PI)

Robert A. Dillman

David H. Atkinson

Amy A. Simon

Michael H. Wong

Thomas R. Spilker

Sarag Saikia

Jing Li

Drew Hope

W. Chris Edwards

Mission Design Center:

NASA Langley Research Center Engineering Design Studio

Hampton University

NASA Langley Research Center

Jet Propulsion Laboratory

NASA Goddard Space Flight Center

University of California, Berkeley

Independent Consultant

Purdue University

NASAAmes Research Center

NASA Langley Research Center

NASA Langley Research Center
2

Mission Science Objectives

Tier-1 Objectives: 

Determine spatial variability in atmospheric properties:

• Vertical distribution of cloud-forming molecules

• Thermal stratification and static stability

• Atmospheric dynamics as a function of depth

Tier-2 Objectives (Tech Search only in this study):

Determine Bulk Composition: 

• Measure abundances of the noble gases (He, Ne, Ar)

• Measure isotopic ratios of H, C, N, and S
3

Science Instruments

NanoChem Atmospheric Composition Sensor:

Vertical distribution of cloud-forming molecules

Atmospheric Structure Instrument (ASI):

Thermal stratification and static stability

Ultra-Stable Oscillator (USO):

Atmospheric dynamics as a function of depth

(Through Doppler Wind Experiment)
Instrument Measurement Mass Power SNAP Data 

Return

NanoChem Atmospheric 

Composition 1.0 kg 0.1 W 1.08 Mbit

Atmospheric 

Structure 

Instrument

Pressure

Temperature

Acceleration

1.3 kg 5.7 W 6.25 Mbit

Ultra-Stable 

Oscillator

Doppler Wind 

Experiment 1.7 kg 3.2 W 0.05 Mbit

(Housekeeping Only)

Total 4 kg 9 W 7.35 Mbit

4

Science Instruments
NanoChem response to ammonia 5

• Measures Changes in Resistivity in response to gas composition

• Sensor Heads can be arrayed up to 16 x16 grid on a single chip

• Under Development at NASA Ames (PI: Jing Li)

NanoChem Advantages:

• Small Sensor Package

• Low Mass, Lowe Power

• Can operate without Vacuum Pump

NanoChem: How it works
6

6

Launched and Operated in Space

Sensitivity demonstrated for:

... CH4, H2O, and NH3, among others

... in Mars and Earth conditions

Need to develop sensitivities for:

... H2S

... in Giant Planet Conditions

Environmental 

Monitoring on ISS

Analyte Sensitivity/Detection Limit

CH4 1 ppm in air

Hydrazine 10 ppb tested

NO2 4.6 ppb in air

NH3 0.5 ppm in air

SO2 25 ppm in air

HCl 5 ppm in air

Formaldehyde 10 ppb in air

Acetone 10 ppm in air

Benzene 20 ppm in air

Cl2 0.5 ppm in N2

HCN 10 ppm in N2

Malathion Open bottle in air

Diazinon Open bottle in air

Toluene 1 ppm in air

Nitrotoluene 256 ppb in N2

H2O2 3.7 ppm in air

Navy MidSTAR-1 

satellite in 2007

NanoChem: TRL = 4 Today
7

NanoChem Commercialization

 Development at NASA Ames

PI: Jing Li

 A/D on NanoChem Attachment

 Power from Phone (~mW)

 Processing on the Phone

 High sensitivity – ppb to ppm 

 Data Transmission through 

Cellular Network
8

Mission Design Assumptions

1. Baseline Carrier Mission: Uranus Orbiter with Probe

Mission Architecture #5 by Ice Giants Flagship SDT:

– 1913 kg Uranus Orbiter

– All-chemical Propulsion (no SEP)

– 50 kg Science Payload on Orbiter

– 321 kg Probe (= Primary Probe = PP)

2. Add SNAP as a Second Probe

3. Deliver PP and SNAP at Uranus with large spatial 

separation

4. PP/SNAP and CRSC trajectories must enable data relay
9

SNAP Study Goals

Enable Future Multi-Probe Planetary Missions:

– Advocated by past Decadal Surveys

– Provide data on spatially varying atmospheric phenomena. 

– 2003 Survey: Advocated for a Jupiter Multi-Probe mission

– 2013 Survey: Emphasized that a second probe can significantly 

enhance the scientific value of a probe mission

– Never realized due to perceived high-cost.

– SNAP Design applicable to Saturn, Uranus and Neptune

(with possibilities for Venus)

SNAP Enables Future Multi-Probe Missions
10

Baseline Carrier Mission

Earth-VEEJ-Uranus (Modified NASA Ice Giants SDT Architecture #5)

• Launch: 5/25/31, VEEJ gravity-assists + Two DSMs

• Launch Vehicle: Atlas V541, 

~4450 kg C3 = 11.9 km2/s2

• 12-year cruise to UOI

Uranus Arrival: May 17, 2043

• Close to 2049 Equinox

• After 2028 Northern Summer Solstice

• Voyager flyby 1986 was during 

Southern Summer Solstice

• Periapsis rp = 1.05 RU

• Capture orbit period = ~142 days
11

Impact on Carrier Mission

Trajectory:

– Release SNAP after Uranus Orbit Insertion

Hardware:

– Mounting & deployment hardware

– Pre-deployment power & data connections

– Orbiter propellant

Software & operations:

– Accommodate second probe delivery and data relay
• Mass in orbit: 1913 kg

• Payload Mass: 50 kg

• UOI rp: 1.05 RU

• Orbital Period: ~142 days

• Mass: 321 kg

• Diameter: 1.2 m, 45°

sphere-cone

• 10-bar* pressure altitude

• Probe release: ~60 days

• EPFA: -20° to -50°

• Mass: 30 kg

• Diameter: 0.5 m, 45°

sphere-cone

• 10-bar* pressure altitude

• Probe release: 30–60 

days

• EPFA: -20° to -50°

Orbiter (CRSC) Primary Atm. Probe (PP) SNAP

Not to scale with Orbiter

*10-bar is requirement for hardware operation for margin, science objective is to reach 5-bar.

From Ice Giant SDT Study SNAP

Baseline Orbiter and Probe: Ice Giant SDT Architecture #5

120 cm

91 cm

50 cm

37 cm

Add SNAP as a Second Probe
13

Interplanetary Trajectory Options

- A broad of catalog of ballistic chemical gravity-assist trajectory options

- SEP options not investigated due to high mass

Launch Launch Launch C3 Interplanetary DSM Arrival UOI ΔV Mass in Flyby Sequence Date Vehicle (km2

/s2) Cruise (yrs) (m/s) Mass (kg) (m/s) Orbit (kg)

Atlas V Earth-VEEJ- 5/25/2031 11.9 12 565 3582.5 1680 1850 541 Uranus

Delta IV Earth-VEJ- 7/18/2031 20.3 10.9 737 5265 2240 2393 Heavy Uranus

Delta IV Earth-VVE- 4/6/2031 25.5 11.5 1063 4751 1580 1885 Heavy Uranus

Baseline

Dual probe delivery architecture possible for 

multiple interplanetary trajectory options
14

Challenges of Multi-Probe Missions

- Deliver PP and SNAP at two significantly different locations 

(latitude, longitude, time-of-day)

- During each probe’s atmospheric descent:

- CRSC used to receive data from probe, relay to Earth

- CRSC must be within 30 degree comm. cone around zenith.

- Each probe must reach at >5-bar while CRSC is in 30-deg cone.
15

Uranus Entry Locations

Accessibility of Entry Locations

- Trajectory gives access to a wide range of 

latitudes and spatial distribution for the entry 

probes

- One probe can enter the night side and the 

other on the day side (After 2028 Northern 

Summer Solstice)
16

Dual-Probe Delivery Trajectories

Trajectory Solution to add SNAP to Ice Giant SDT Architecture #5
17

Con-Ops: Dual Probe Delivery
18

Overall Mission ConOps

 Overall mission ConOps with critical events

 T = 0 day is UOI

Not to Scale
19

Atmospheric Entry & Descent

Descent Chute Diameter = 0.1 m Stabilizer

Separation Chute Diameter = 1.5 m
20

Atmospheric Entry & Descent

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

05 10 15 20 25 30 35 40 45 50

Pressure Level [bar]

Time [min]

Pressure Level [bar]

-200

300

800

1,300

1,800

05 10 15 20 25 30 35 40 45 50

Altitude Above 1-bar [km]

Time [min]

Altitude Above 1-bar [km]

40-min Communication Cutoff

5-bar Threshold Mission Target
21

Entry & Descent Analysis

0.0

500.0

1,000.0

1,500.0

2,000.0

2,500.0

3,000.0

3,500.0

0 50 100 150 200

Heating Rate [W/cm2]

Time [sec]

Heating Rate [W/cm2]

0.0

50.0

100.0

150.0

200.0

0 50 100 150 200

Acceleration [g]

Time [sec]

Acceleration [g]

0

50

100

150

200

250

300

0 50 100 150 200

Dynamic Pressure [kPa]

Time [sec]

Dynamic Pressure [kPa]

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

0 50 100 150 200

Air Speed [Mach]

Time [sec]

Air Speed [Mach]
22

Link Analysis

0

1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

-2.00E+03

0.00E+00

2.00E+03

4.00E+03

6.00E+03

8.00E+03

1.00E+04

1.20E+04

0 10 20 30 40 50 60

Integrated Data Volume (bits)

Data Generation Rate (bps)

Time (min)

Data Gen. Rate Int. Data Vol.

0

1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

0

1000000

2000000

3000000

4000000

5000000

6000000

7000000

8000000

0 10 20 30 40 50 60

Generated Data Volume (bits)

Delivered Data Volume (bits)

Time (min)

Int. Data Vol. DelDataVol

Data Generation 3500 bps Data Rate Worst-case 

Link Analysis takes account of:

- Atmospheric Radio Absorption

(NH3 + CH4)

- Attenuation through Link Range

- Transmitter/Receiver Antenna Gain

- Link Geometry

- Receiver Noise Model

2.2 GHz (S-Band)
23

Baseline SNAP Design Summary

 0.5 m diameter, 30-kg, 45° sphere-cone heat shield

 SNAP is released ~30 days before entry (from ~142-day orbiter orbit)

 After PP, SNAP enters prograde with EFPA between -40° and -45° and V = 22.4 km/s

 SNAP enters on the day side of Uranus

 Orbiter-SNAP separation 36000–13000 km during mission (~40-mins contact time)

• Short distance range enables sufficient data rate

 Deceleration and aerothermal conditions all well within design limits

 Fore-body TPS = HEEET; Aft-body TPS = PICA

Entry Conditions of SNAP

Parameter Values

Peak Heat Rate, W/cm2 3250–3750

Stagnation Pressure, bar 2.75–3.75

Heat Load, J/cm2 29227–34515

Peak Inertial Load, Earth G’s 196–270
24

Avionics

Transmitter

Radio-Isotope

Heater Unit

Descent Chute

Antenna

Separation Chute

ASI (Accelerometer)

NanoChem ASI Inlet Mast

Chute Mortar

USO

Clock

ASI (Temperature)

ASI (Pressure)

Batteries

TPS (PICA)

TPS (HEEET)

Baseline Hardware Configuration
Component Mass [kg] Subtotal Mass

Foreshell TPS (HEEET) + Structure 5.74

Aftshell TPS (PICA) + Structure + Separation Mechanism 4.15

Aeroshell Total 14.03 kg

Descent Module Structure 2.1

Parachutes 0.4

Science Instruments 4

Engineering Subsystems 4.2

Descent Module Total 9.85 kg

Atmospheric Entry Mass Total 23.88 kg

Mass Margin (25%) 6.12 kg

Total Probe Mass 30 kg 25

Probe Mass Summary
26

Sub-system/ Instruments Power

Ultra-Stable Oscillator 3.2 W

ASI 5.7 W

Nano-Chem Sensor 0.1 W

Avionics 4 W

Radio Transmitter 50 W

Accelerometers 0.1 W

Total 63.1 W

Probe Power Summary

Phase Energy Requirement, Wh Battery Mass, kg Number of Batteries

SNAP Mission 164 0.257 3

In left, we assume use of x3 RHUs.

Battery-powered heaters are also possible.

After probe release until atmo. entry

 SNAP needs 3W of heating.

For 30-day “coast”...

Li-Ion (current, 145 Wh/kg) = 21 kg

Li-Ion (future, 400 Wh/kg) = 7.5 kg

Li/CFx (639 Wh/kg) = 4.7kg
27

Mass Impact on Carrier Mission 

by Addition of SNAP

• SNAP margined mass = 30 kg. 

• Requires additional mass to baseline Uranus mission: 

– Probe Support Systems on the Orbiter

– Propellant on the Orbiter

Systems/ Subsystem Mass, kg Margined Mass, kg Margin

Probe Support Systems Total 4 5.3

Spin ejection device 3 4 30%

Harness/ umbilicals 1 1.3

SNAP Mass 23.88 30 25%

Orbiter SNAP Support Propellant 30 36 30%

Total Mass Addition to Carrier Mission 58 72.3
0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042

SNAP Cost and Schedule By Year

Science Project Management

Systems Engineering Safety and Mission Assurance

Entry System Science Modeling and Analysis

EV Flight System Descent Module

EV System Assembly, Integration and Test SC Separation System Flight Hardware

Spacecraft Integration & Test Support / ATLO Project Reserve

Est. SNAP Cost = 74.8M (FY18$)

IGSDT Arch. #5 Cost = 2B (FY15)

$75M = 4% Δcost to enable

a multi-probe mission

2031 Launch

2043 2044

2042 Arrival

Cost Analysis
Technology Needs

 Instrument/Sensor Technology

NanoChem is TRL = 4 today (Under Dev. at Ames)

 Thermal Protection System:

HEEET is needed for low density (Under Dev. at Ames)

 Power - Batteries: 

Low-temp., High Specific Energy Batteries alleviate 

need for RHUs

 Electronics:

Low-survival temp will reduces heater power needs
Study Components

– Science Objectives*

– Top-Level Design Assumption 

(Pick Baseline Mission)*

– Interplanetary Trajectories*

– Dual-Probe delivery options*

– Atmospheric Characterization*

– Atmospheric Entry 

and Descent Analysis*

– Con-Ops*

– Link Analysis* * Items Included in this Presentation

– Instrument Technologies*

– Mechanical Design*

– Thermal Analysis

– Power*

– CDH + Electronics

– Risk

– Cost*

Add SNAP as a Second Probe to 

a Future Uranus Orbiter with Probe mission
31

Total Data Return = 7.3 Mbit

Total Mass Addition to Carrier Mission: 72.3 kg

Total Estimated Cost: 74.8M (FY18$)

Enabling Technologies: NanoChem & HEEET

Enhancing Technologies: Better Batteries

SNAP: Enable Future Multi-Probe Missions 

SNAP Design Summary

Dual-Probe Trajectory Solutions Found

SNAP Mass: 30 kg (Instrument Mass = 4 kg)
Science Objectives:

Tier-1 Objectives: Determine spatial differences of the following 

atmospheric properties from the Main Probe entry site: 

1. Vertical distribution of cloud-forming molecules

2. Thermal stratification

3. Wind speed as a function of depth

Tier-2 Objectives: Augment Main Probe Science Objectives: 

4. Measure abundances of the noble gases (He, Ne, Ar)

5. Measure isotopic ratios of H, C, N, and S

Mission Overview:

Baseline Mission Configuration: 

Add SNAP to Uranus Orbiter and Probe Mission

Orbiter delivers Main Probe and SNAP to Uranus

Baseline Spacecraft Configuration:

Mass: 30 kg

Probe Diameter: 50 cm

Probe Power: Primary Batteries

Heatshield Material: HEEET

Notional Payload:

NanoChem: Detect cloud-forming molecules 

Atmospheric Structure Instrument: Measure thermal profile

Ultrastable Oscillator: Atmospheric Dynamics

Team Members/Institutions

Kunio M. Sayanagi | Hampton University

Robert A. Dillman | NASA Langley Research Center

David H. Atkinson | Jet Propulsion Laboratory

Amy A. Simon | NASA Goddard Space Flight Center

Michael H. Wong | University of California, Berkeley

Thomas R. Spilker | Independent Consultant

Sarag Saikia | Purdue University

Jing Li | NASA Ames Research Center

Drew Hope | NASA Langley Research Center

W. Chris Edwards | NASA Langley Research Center

Supported by: NASA Langley Research Center Engineering Design Studio
33

BACK UP SLIDES
34

Engineering Design Studio (EDS), NASA Langley Research Center

 Support PI-led Mission Design & Proposal Development

 Concurrent Engineering Design Capability in Dedicated Room

 Access Strengths of NASA Langley Research Center

 Atmos. Entry, Descent & Landing

 Remote-Sensing Measurements

 Atmospheric In-Situ Measurements

 Aeronautics

 Proposal Development Support

 Blue/Red Team Reviews

 Strength, Weakness, Opportunities, Threats (SWOT) Analysis

 Mission Cost Analysis

 Proposal/Project Budget Development

 Graphics Design

NASA LaRC Engineering Design Studio 

Mission Design Center
35

 Dual probe delivery possible for multiple trajectory options

 SNAP mission concept is applicable to many interplanetary trajectories

Accessibility of Entry Locations

Launch date Launch 

Vehicle

Flyby 

Sequence

Launch C3

(km2/s2)

IP TOF 

(yrs)

DSM 

(m/s)

Arrival 

Mass (kg)

UOI ΔV 

(m/s)

Arrival V∞

(km/s)

Arrival 

Decl., deg

Mass in 

Orbit (kg)

4/6/2031 Delta IV 

Heavy

Earth-VVEUranus 25.5 11.5 1063 4751 1580 8.04 71° 1885

Alternate Interplanetary Trajectories
 Shows hyperbolic approach 

trajectories of orbiter + SNAP (blue, 

right) and primary probe (red)

 Shows elliptical captured orbit of 

orbiter (blue, left) and elliptical 

trajectory of SNAP (green)

 30° Margined HWHM beam cone is 

centered around the negative of 

planet-relative velocity vector of the 

probes as they undergo entry and 

descent

 Orange cone: Ongoing probe entry 

mission but no orbiter-probe 

contact

 Green cone: When orbiter is in 

contact with the probe

Orbiter-SNAP 

hyperbolic 

approach

SNAP elliptical 

approach

AP hyperbolic 

approach

Orbiter capture 

orbit

rbiter capture 

orbit

– PAP enters on the night side of Uranus

– SNAP enters on the day side of Uranus

36

Concept-of-Operations: Dual-Probe Delivery

P

O
0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

2025 2026 2027 2028 2029 2030

SNAP Cost Through Development

Science Project Management

Systems Engineering Safety and Mission Assurance

Entry System Science Modeling and Analysis

EV Flight System Descent Module

EV System Assembly, Integration and Test SC Separation System Flight Hardware

Spacecraft Integration & Test Support / ATLO Project Reserve

2027 2028 2029 2030 2031 2032

Cost Analysis
Baseline Hardware Configuration