Plans for an Interstellar Probe Ralph L. McNutt, Jr. Johns Hopkins University Applied Physics Laboratory Pasadena Convention Center International Academy of Astronautics (IAA) Day Session Room 06 – Room 101 Pasadena, California, USA Saturday 14 July 2018 3:30 PM – 4:00 PM held on the occasion of the 42nd COSPAR Scientific Assembly What is “Interstellar Probe”? • “Interstellar Probe” is a mission through the outer heliosphere and to the nearby “Very Local” interstellar medium 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 - Heliosphere: How does the heliosphere interact with our galactic surroundings? - Kuiper Belt Objects: Discover new worlds to understand the origin of our solar system - Circum-Solar Dust Disk: Reveal the unseen 3D dust distribution to understand planetary formation • Interstellar Probe can pave the way, scientifically, technically, and programmatically for longer interstellar journeys that would require future propulsions systems IAA Academy Day 14 July 2018 2 Current Status • The Johns Hopkins University Applied Physics Laboratory has been tasked by the NASA Heliophysics Division to (re-)study the mission (as of 13 June) • Provide science and technical input to help support the next round of “Decadal Surveys” in the United States - Focus on the time frame in the next Decadal: 2023 – 2032: Can we fly then? - Assess the science: Does the case remain compelling? - Assess technical readiness for a launch **NO LATER THAN 2030** • Reach out to the broadest range of scientific and technical stakeholders throughout those communities - This meeting, COSPAR (Monday and Tuesday), the upcoming American Geophysical Union meeting and others - Use the COSPAR Panel on Interstellar Research (PIR) to reach out to the International Community • Conclude this effort in nine months, reporting back to NASA by February 2019 • We need your help and input IAA Academy Day 14 July 2018 3 A Mission a Long Time in the Making IAA Academy Day 14 July 2018 4 …Which Began an Enduring Notion Deep Space Probe* (1965) • 1960: The Space Studies Board “Outer Solar System Probe to be aimed away from Jupiter Galactic Probe* (1967) the Sun…” Pioneer 10/11 (1980) • 1965: Dr E. Parker advocates mission to Voyager (1977) heliospheric boundary region • 1977: Voyager-1 launch New Horizons (2006) • 1990: The Interstellar Probe (Holzer et al., 1990) • 2001: NIAC Study, APL • 2002: JPL Study • 2006: Innovative Interstellar Explorer (Fiehler et al., 2006) • 2009: The Interstellar Heliopause Mission (Wimmer-Schweingruber et al., 2009) • 2015: Keck Institute of Space Studies Parker Solar Probe (2018) (KISS) Report/Proposal Interstellar Probe (<2050) IAA Academy Day 14 July 2018 5 Basic Questions Have Not Changed What is the nature of the nearby interstellar medium? How do the Sun and galaxy affect the dynamics of the heliosphere? What is the structure of the heliosphere? How did matter in the solar system and interstellar medium originate and evolve? IAA Academy Day 14 July 2018 6 Heliosphere Concept: Beginnings Definition of “heliosphere”: “…the region of interplanetary space where the solar wind is flowing supersonically.” Davis (1955) Dessler (1967) Dessler (1967) IAA Academy Day 14 July 2018 7 The Initial View from Voyager • Only Voyager 1 has (likely) passed through the heliopause into interstellar space • Ongoing measurements continue to show variations - Driven by the Sun (inside?) - Driven by the VLISM (outside?) IAA Academy Day 14 July 2018 8 What *IS* New • Remote observations of energetic neutral atoms (ENAs) from the interaction region (IBEX and Cassini) • In situ particle measurements beyond the termination shock (Voyager 1 and 2) • The first detailed look at a Kuiper Belt Object (KBO), namely Pluto, and in situ measurements of pick up ions in the outer heliosphere (New Horizons) IAA Academy Day 14 July 2018 9 The Shape Remains in Debate Parker 1961, Diagram from McComas et al. From Dialynas et al (2017), The bubble-like shape of the heliosphere observed by Voyager and Cassini IAA Academy Day 14 July 2018 10 Interstellar Probe Humanity’s First Explicit Step Into Interstellar Space Target 1: Interstellar Medium and Heliosphere Target 2: Circum-Solar Voyager 1 (Active) Dust Disk Pioneer 11 (Lost) Pioneer 10 (Lost) Interstellar Probe New Horizons (Active) Target 3: Kuiper Belt Objects Voyager 2 (Active) Target 4: “Planet Nine”? IAA Academy Day 14 July 2018 11 Interstellar Probe Targets The Interstellar Medium Exploring new astrophysical plasma conditions governing the shape of our heliosphere, and others. IAA Academy Day 14 July 2018 12 Interstellar Probe Targets Unexplored Worlds of KBOs Flyby images of Pluto revealed exotic plains of frozen nitrogen and dramatic mountains of water-ice bedrock. The dwarf planet, Quaoar is located at 40-50 AU. It in its last stages of losing its methane atmosphere and may have cryo- volcanism (Jewitt et al., 2004). IAA Academy Day 14 July 2018 13 Interstellar Probe Targets Circum-Solar Dust Disk The dust cloud surrounding the solar system is obscured by the zodical dust cloud. Venturing outward will for the first time reveal the circum-solar dust cloud that hold important clues to planetary-system formation and evolution. The spiral pattern above indicates a young planetary system in formation (Grady et al., 2009). IAA Academy Day 14 July 2018 14 Interstellar Probe Targets Planet Nine? Ten? Planet TenNine ~1100 AU ~280 AU Clustering of KBOs in perihelion argument may suggest a presence of a large planet 10 times the mass of Earth with e=0.6 and semimajor axis of 700 AU (Batygin and Brown, The newly discovered 2015 BP519 may 2016). be the first purely trans-Neptunian member of the Planet-Nine-induced high-inclination population (Becker+2018). IAA Academy Day 14 July 2018 15 Interstellar Probe Payload – A First Cut • Mass not to exceed (NTE) ~40 kg • Power NTE ~40 W • Interstellar Medium and HeliospHeric Suite - Particle, Plasma and Magnetic Fields Instrumentation: exploring the new astrophysical conditions governing the shape of our heliosphere The ENA Camera INCA on board the Cassini mission and its second generation version and other astrospheres developed for the ESA JUICE Mission (Krimigis et al., 2004; Mitchell et al., 2016) - ENA Camera: OBtaining the first image of our gloBal heliosphere to understand how we compare with others - Dust Detector: Spatial and size distriBution of circum-solar dust • Imaging Systems - Optical: Fast flyby imaging of KBOs, precision The ZEBRA instrument concept consists of the High- IR Instrument on board astrometry, deep-sky survey resolution Absolute Module (HAM) with a 15 cm Rosetta. telescope, and the Wide-field Absolute Module - Infra Red: Surface imaging, gloBal dust distriBution (WAM) with a 3 cm telescope (Bock et al., 2012). IAA Academy Day 14 July 2018 16 Example Spacecraft Span 250 kg to 500 kg • Pluto/New Horizons • Ulysses • Pioneer 10 478.3 kg 366.7 kg 251.8 kg IAA Academy Day 14 July 2018 17 Propulsion Approaches for Interstellar Probe • High solar system escape speed required • Twice the asymptotic speed of Voyager 1 is ~34 km/s - Now 3.6 AU/year at 141 AU from the Sun – hence twice Voyager 1 speed is 7.2 AU/year ~ 34 km/s • Six times would be over 20 AU per year (less than 1 year to Uranus) • Passive: Launch C3 and unpowered gravity assists • Active: Powered gravity assists and in-space propulsion IAA Academy Day 14 July 2018 18 In-Space Propulsion Does Not Solve the Problem – Underpowered for the Mass • Solar Electric Propulsion (SEP) or the use of Solar Sail Propulsion becomes ineffective outside of ~5 AU at the most (Jupiter’s orbit) • Radioisotope Electric Propulsion (REP) requires ~1 kWe radioisotope power system (RPS) • Nuclear Electric Propulsion (NEP) requires a Prometheus-like nuclear power system (NPS) at half the specific mass (or less) and good for autonomous operation for > 10 years • The current state-of-the-art of all of these technologies has too large a specific mass (mass/power ratio) IAA Academy Day 14 July 2018 19 The SLS Block 1B May be the Solution • Early ”solar probe” (1962) advocated “Saturn C-1 plus H2-F2 stages” • Original “Voyager” program to Mars used Saturn V (1967) • Ames Workshop and NRC study (2008) investigated Ares V • Initial ”cuts” made with SLS with Boeing and KSC Launch Services (2014-2015) IAA Academy Day 14 July 2018 20 Mission Concept(s) Speed, speed, speed • Option 1: Jupiter Gravity Assist (JGA) - Burn all your C3 directly after launch with passive JGA appears most Benefitial - Asymptotic speed ~7.6 AU/year - Required C3: 300 km2/s2 • Option 2: JGA + Oberth Maneuver Near the Sun (“Rendezvous With Rama”) - Reverse JGA to dump angular momentum - Fall in to the Sun without actually hitting the Sun, maximizing your incoming speed - Burn all your fuel at perihelion - Asymptotic speed: up to 8.3 AU/year 2 2 - Required C3 : 110 km /s • You need a BIG ROCKET. IAA Academy Day 14 July 2018 21 The Reality of Interstellar Space Flight Parker Solar Probe Enables an Oberth Maneuver § 1000 AU within 50 years requires 2 RS 892 kg § ∆v=14.6 km/s at 4 RS § or § ∆v=10.3 km/s at 2 RS § Star 48B provides ∆v≤4 km/s 3 RS § We need to at least double this 539 kg 8.3 AU/year 4 RS 293 kg 9.5 RS 153 kg Parker Solar Probe in the clean room at Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland. 6.7 AU/year IAA Academy Day 14 July 2018 22 Interstellar Probe: Critical Trade-Off Studies • Mass - S/C range 300-800 kg (New Horizons 478.3 kg) - P/L ~40-50 kg (New Horizons 30.4 kg) - Thermal Protection System 150-900 kg (PSP 98.9 kg incl structure) • Power: GPHS RTG is the best we have ever had - Galileo, Cassini, Ulysses - Voyager (MHW RTG) will last to mid-2020’s - Pu-238 production program has turned a corner • Communication: Solid, near-term, tested engineering PSP Thermal Protection System being installed in the large vacuum chamber at GSFC.