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Gravity Assist here Interstellar Probe: A New Mission for a New Decade

Ralph L. McNutt, Jr.

The John Hopkins University Applied Physics Laboratory, USA

SH32C-01 The Interstellar Probe Mission: Walter E. Washington Convention Center 10:20 AM – 10:32 AM Study Findings and Next Steps I Room: (CC) 207B Wednesday 12 December 2018 Paper 1, 12-minute oral Washington, DC, USA What is “Interstellar Probe”?

• “Interstellar Probe” is a mission through the outer and to the nearby “Very Local” or VLISM (0.01 parsecs = ~2,000 AU =~10 light days)

• Interstellar Probe uses today’s technology to take the first explicit step on the path of interstellar exploration

• Interstellar Probe can pave the way, scientifically, technically, and programmatically for longer interstellar journeys that would require future propulsions systems

4 Interstellar Probe: A 58-year(+) Old Idea

• 1960: The Space Studies Board “Outer probe: to be aimed away from the …” • 1965: Eugene Parker advocates mission to heliospheric boundary region Deep (1965) Galactic Probe (1967) • 1977: Voyager-1 launch /11 (1980) • 1990: The Interstellar Probe (Holzer et al., 1990) • 1999: JPL Study (NASA STDT) • 2001: NIAC Study, APL Voyager (1977) • 2005: Innovative Interstellar Explorer (McNutt et al., 2005) (“Vision Mission”) • 2009: The Interstellar Heliopause Mission (Wimmer-Schweingruber et al., (2006) 2009) • 2015: Keck Institute of Space Studies (KISS) Report

5 Two Distinct Questions

• What should we do? • The question for a future Science Definition Team or equivalent and the science community overall

• What could we do? • The question at hand for this study

6 Current Study • The Johns Hopkins University Applied Physics Laboratory has been tasked by the NASA Heliophysics Division to (re-)study the mission (as of 13 June 2018)

• Provide input to help support the next round of “Decadal Surveys” in the United States - Focus on the time frame in the next Heliophysics Decadal: 2023 – 2032: Could we launch a scientifically compelling mission that decade? – technical question but not without science implications

7 The Science Touches Across Disciplines

Potential for Target 1: Interstellar Medium expanded and Heliosphere science Target 2: Circum-Solar Dust across all of Disk NASA’s Science Target 3: Objects Mission Directorate Target 4: (Possible) Large Trans-Neptunian Planets

8 Critical Trade-Offs Are Not New

• Mass: Driven by flyout speed and • Communication: Solid, near-term, payload (P/L) capability tested engineering - S/C range 300-800 kg (New Horizons 478.3 kg) - Ka-band at ~640 bps and more at 140 AU and - P/L ~40-50 kg (New Horizons 30.4 kg) beyond - Thermal Protection System 150-900 kg (PSP - Optical laser comm might achieve ~10 kbps, but 98.9 kg incl structure) requires extreme pointing stability; lifetime needs investigation • Power: GPHS RTG – life efficiency and lifetime for use in vacuo • Trajectory/Propulsion/Launch - Galileo, Cassini, Vehicle: Keys for implementation - Voyager (MHW RTG) will last to mid-2020’s - In-depth trajectory analysis including accurate mechanical and rhermal designs together with - Pu-238 production program has turned a corner launch vehicle (LV) providers - Propulsion technology and engineering assessment of what works and what does not

9 Notional Concepts Span 250 kg to 825 kg Pioneer 10/11 to /2

• Voyager • New Horizons • Ulysses • Pioneer 10 825.4 kg 478.3 kg 366.7 kg 251.8 kg Current example for study

10 Mission Concept(s) Speed, speed, speed

• Option 1: Unpowered Jupiter (JGA) - Burn all stages directly after launch - Follow with optimized prograde JGA • Option 2: Active Jupiter Gravity Assist - Take one stage to Jupiter and burn it at optimized perijove - Opposite of orbit insertion maneuver • Option 3: JGA + Oberth Maneuver Near the Sun - Reverse JGA to dump angular momentum - Fall in to the Sun without actually hitting the Sun, maximizing your incoming speed - Burn final stage(s) at (close) perihelion • You need a (REALLY) BIG ROCKET

AGU Fall Meeting 2018 - Session SH32C The Interstellar Probe Mission: Study Findings and Next Steps I - 12 December 2018 11 Pre-decisional; for planning and discussion purposes only Establish common Ground Rules and Thermal Control System for deep-space use of kick stages

• Nine stages / motor systems evaluated for functionality and propulsive scenarios across 31 configurations • In progress

12 (SLS) Offers Possibilities – with Upper Stages Option 1: Region of interest

2 2 200 ≤ C3 ≤ 260 km /s

478.3 kg 7 AU/yr

13 Realities of Flight Near the Sun

• You can’t “go at night” • At end of (PSP) mission (in seven years) we will be at a perihelion passage of 9.86 Rs - Not close enough! • But PSP may be a pathfinder to solutions - Does not solve the problem st - 1 perihelion at 35.7 Rs on ~6 November 2018

14 Option 3: Shield Estimates ( 48BV) • Accommodate New Horizons – like Interstellar Probe: mass and layout as a model • Options 1 and 2: Estimate performance • Option 3: Estimate thermal

shield for perihelia of 3 RS, Thermal 4 RS, and 5 RS analysis at - Verify thermal performance

5 Rs - Estimate thermal shield mass ~2200°C to - Estimate system performance 2600°C (hottest)

15 Designing for Different Perihelia: CASTOR 30XL

• Option 3 configuration with Increasing temperature, shield mass à notional New Horizons – like

and CASTOR 30XL 5 Rs 4 Rs 3 Rs stage with thermal shields for 3

RS, 4 RS, and 5 RS perihelia

Option 3 engineering studies in progress Estimate is now > 12 AU/yr

16 Summarizing Some Possibilities

See poster SH33C-3660 THIS AFTERNOON

Community input to an Interstellar Probe concept – Workshop at the Explorers Club 10-12 October in New York City

17 Both Voyagers have now “left the building”…

…but the real journey has onlyFrom Dialynas just et al (2017),begun The . bubble-like shape of the heliosphere observed by Voyager and Cassini

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