Launch Vehicle and Flight System Considerations - Interstellar ...

Launch Vehicle and Flight System
Considerations
4th Annual Interstellar Probe Exploration Workshop
10:30 AM – 10:50 AM, Thursday, 30 September 2021
Ralph L. McNutt, Jr.
Pragmatic Interstellar Probe Mission Study Principal Investigator
ralph.mcnutt@jhuapl.edu

Implementation “Requirements” for an Interstellar Probe
 • An interstellar Probe mission must be capable for making a
 ”significant” penetration into the nearby - aka (“Very Local”) –
 Interstellar Medium in a “reasonable” amount of time
 • The terms “significant” and “reasonable” have varied over the
 past 60 years – usually reflecting the perceived ”near-term
 technology horizon” of the time.
 • Implied speeds have ranged from 5 au/yr to ~120 au/yr to
 distances of 150 au to 0.1 ly (6,320 au) with travel times of ~20
 to 50 years
 • Asymptotic escape speeds from the Sun in excess of ~10 au/yr
 have been – and continue to be - problematic

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Implementation “Solutions” for an Interstellar Probe
 • All posited historic “solutions” have called for in-space, low-thrust propulsion
 - Required technology somewhere past the then-current (i.e., at the time of the study) state of the art (SOA)

 Solar Sail
 IKAROS 315 kg, 196 m2
Solar Oberth Maneuver (SOM) Nuclear Electric Propulsion (NEP) 1607 g/m2 >>> 1.54 g/m2
1929 – ∆V = 5 km/s 2003 – 2005 Project Prometheus
 Lightsail 2 5 kg, 32 m2
Implied rp = 1.53 Rs Life Cycle Cost Estimate $21.5B RY
 156 g/m2 >> 1.54 g/m2
Vescape = ~15 au/yr Requires ≤ 30 kg/kW system
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Solar Oberth Maneuver (SOM) – 1
• Extended study as part of this effort
• Spacecraft design that “closes” with the science trades
• Advanced thermal shield material can (on paper) lower accessible perihelia to ~2 solar radii (from the
 CENTER) of the Sun

• Option 3 – Solar Oberth maneuver (powered solar gravity assist - ~900-kg spacecraft plus
 ~1,600 kg thermal shield
• Potentially Highest Performance Example: 2 Rs perihelion with Orion 50XL

 Option 1 Mass = 860 kg Option 1 Mass = 251.8 kg (P10)
 Asymptotic escape speed Asymptotic escape speed
 Vesc = 8.0498 au/yr Vesc = 8.9032 au/yr
 Launch ! = 108.29 " / " Launch ! = 108.29 " / "
 At Sun ∆ = 2.0536 / At Sun ∆ = . / 
 Time to 400 au = 52.73 years Time to 400 au = 48.08 years
 BASELINE S/C – science ”PIONEER 10” S/C – science no
 closure longer closes w/faster speed
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Solar Oberth Maneuver (SOM) – 2
• Less massive Pioneer 10 spacecraft allows for a speed increase –
 but only by about 12%
• That spacecraft design does NOT “close” with the current science
 trades
• Most of the thermal shield mass is associated with protecting the kick
 stage (Orion 50XL)

 ✘
• Lowering the perihelion to 1 solar radius (not possible) would only
 increase the speed by a factor of ~21/4 = 1.19 (~20%)

 ✘
• IF one could replace the solid fuel with zero boil off (ZBO) liquid
 hydrogen (LH2) AND replace the Orion 50XL mass with a nuclear Option 1 Mass = 251.8 kg (P10)
 thermal rocket (NTR) engine with a specific impulse of 900 s Asymptotic escape speed
 (PEWEE-1 test) THEN the flyout speed could be increased to 16.7 Vesc = 16.6898 au/yr
 au/yr Launch ! = 108.29 " / "
• Even with ZBO LH2 this does not close – the Small Nuclear At Sun ∆ = . / 
 Rocket Engine (SNRE) design engine is ~7 times the mass of the Time to 400 au = 27.42 years
 EMPTY Orion 50XL motor (which includes the propellant “tank" “Orion 50XL” Isp = 900 s

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Nuclear Electric Propulsion (NEP)

 ✘
• One U.S. flown reactor SNAP – 10 in April 1965; satellite failed 6,100 kg+
 at 43 days; reactor scrammed and parts still in nuclear-safe 3,336 kg
 orbit (waste)
• SNAP program: 1956 – 1973, > ~ $ 7.8 B in now-year dollars heat
 rejection
• Need unattended / autonomous reactor operation for ~10 years segment
• Major mass driver is waste heat rejection radiator system
• Prometheus reactor module development cost $4.165 B

 ✘
• “Analysis of the critical path to launch shows the Reactor
 Module (and associated Power Conversion) development
 and testing activities as the most critical path.” -Project
 Prometheus Final Report

Technology Horizon (2030) + Programmatics / Cost + Risk
are problematic (at best)

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Solar Sail – 1
• To enable rapid solar system escape need
 !"#$% &'%$( ($"!$)!'* +(#&&,(# -'(.# 0.234 56!"
 - “Lightness number” = ($/!)$)!'*$%-'(.#
 = ≥1
 7#$$
 - Release point from a sufficiently high speed – typically heliocentric radii of 20 Rs
 to 25 Rs have been discussed
 - è an additional heat shield (= mass ) is required
• Sailcraft to date have been too small to provide science closure
 to the mission here
 - No engineering closure either ≪ 1
 - Solar Cruiser: 1,650 m2, 90 kg spacecraft
 0,924
 § ~1.54 = 0.03 ≪ 1
 :4,444

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Solar Sail – 2
• Parker Solar Probe could come close to
 having the capability to carry instruments
 for science closure
 - Includes thermal shield capable of solar
 approach to ~ 10 Rs

 ✘
 - 685 kg mass è =1 for a sail area of 0.44

 ✘
 km2 or 667 m on a side
 - Each of four 472-m long spars would have
 to carry its share of increased radiation
 pressure near the Sun
• Materials strength issue past current SoA

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Ballistic Missiles to Space: 1 – Concept to First Use
• Development of space launch vehicles is an expensive,
 dangerous, and time-consuming undertaking
• Theoretical underpinnings advanced by Tsiolkovskii in the
 (then) Russian Empire (1911)
• Similar work undertaken by Goddard (U.S), Oberth (Germany),
 and Esnault-Pelterie (France)
• Goddard demonstrated first liquid-fueled rocket 16 March 1926

• Development of 1st operational
 system (V2 Vergeltungswaffe 2)
 during World War II (Germany)
 - 6,048 built; 3,225 launched; V2 and precursor
 V1 estimated cost ~$40B 2015 USD
 - The V2 holds the record for largest
 number of rockets of one model built
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Ballistic Missiles: 2 – Humans to Orbit and the Moon
• Captured systems and personnel by U.S. Army forces and Soviet Army forces were the basis for the
 Space Age and the Moon Race and Ballistic Missile component of the Cold War
• Largest systems development for human landings on the Moon (1961 – 1972)
 - U.S. Saturn V – 15 builds (13 successful launches + 2 museum exhibits): 6 human lunar landings
 - Soviet N-1 – four launches (non-crew); all failed

 Soviet N-1 Baikonur F-1 engine was key to Saturn V; 8-yr development for $1.77B FY91$
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2008: General Question of NASA Science
Missions Enabled by the Constellation
Launch System

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2009 – 2017: Exploring Ballistic Approaches - IACs
• Enabling Interstellar Probe (60th IAC – Daejon 2009)

• Interstellar Probe: Impact of the Voyager and IBEX Results
 on Science and Strategy (61st IAC – Prague 2010)
• Enabling Interstellar Probe with the Space Launch System
 (SLS) (65th IAC – Toronto 2014)
• Enabling Interstellar Probe: Space Launch System (SLS)
 Trades (66th IAC – Jerusalem 2015)

• Interstellar Probe: Requirements (67th IAC – Guadalajara
 2016)
• Near-Term Exploration of the Interstellar Medium (68th IAC –
 Adelaide 2017)

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2018 – 2021: Pragmatic Interstellar Probe Effort
• Near -Term Interstellar Probe: First Step (69th
 IAC – Bremen 2018)

• An Interstellar Probe for the Next Heliophysics
 Decadal Survey (70th IAC – Washington 2019)

• A Pragmatic Interstellar Probe Mission: Progress
 and Status (71st IAC – The CyberSpace Edition
 2020)

• Interstellar Probe – Destination: Universe! (72nd
 IAC – Dubai 2021)

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Upper
Stages Star48BV Star48GXV Orion 50XL

Centaur D Atlas V Centaur

 Castor 30XL Castor 30B

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Representative Stage
Configuration Trades

 298 m3
 9.9 m
 331 m3

 9.2 m
 4.2 m
 85 m3

 9.8 m
 7.1 m

 8.3 m

 328 m3
 205 m3

 259 m3
 Atlas V Atlas V
 Centaur / Star Centaur / Star Castor 30XL / Castor 30B /
 Atlas V
 Centaur D 48BV 48GXV Star 48BV Star 48BV
 Centaur
 Long Shroud

2018 – 2020:
MSFC Developed
Performance
Details
(“traditional”)

• For full up analysis
 required mass versus
 C3 curves for a variety
 of SLS and stage
 configurations
• MSFC provided these
 for SLS Block 2 Cargo
 and a requested
 variety of upper stage
 configurations
• SLS Block 1B+ Cargo
 now referred to as
 SLS Block 2 Cargo

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2018 – 2020:
MSFC Developed
Performance
Details
(”semi-log”)

• For full up analysis
 required mass versus
 C3 curves for a variety
 of SLS and stage
 configurations
• MSFC provided these
 for SLS Block 2 Cargo
 and a requested
 variety of upper stage
 configurations
• SLS Block 1B+ Cargo
 now referred to as
 SLS Block 2 Cargo

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