GRC POP Formulation Framework

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Implications of NTP for Human Exploration of the
Moon, Mars, and Near Earth Objects presented
by Dr. Stanley K. BorowskiPropulsion Controls
Systems Analysis Branch W 216-977-7091, e-mail
Stanley.K.Borowski_at_grc.nasa.gov at the Nuclear
Emerging Technologies for Space (NETS-2009)
Topical / ANS 2009 Summer MeetingHyatt Regency
Atlanta HotelAtlanta, GA Tuesday, June 16,
2009
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Crewed NTR Mars Transfer Vehicles Concepts (1968
-1973)
1982 Opposition-class Mars Landing Missionusing
Common Modular NTP StagesBoeing (Jan. 1968)
von Braun Mars Landing Mission using Tandem NTP
Stages (3) and Convoy Mission Mode (August
1969)
Alternate von Braun Approach with Single
Propulsion Stage LH2 transfer from in-line and
tandem drop tanks (Non-Integral Burn option)
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Werhner von Brauns Integrated Space Plan for
NASA(1970 - 1990)
Source NASAs Office of Aeronautics, Exploration
and Technology, presented to
Stafford Synthesis Team in 1991
Modular 75 klbf NERVA NTR Stage forMoon / Mars
Mission Applications
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NTR / BNTR-powered Moon / Mars Transfer Vehicle
Concepts Developed by GRC (1989 - 2000)
Design Transition from Single Large NTR to
Clustered Smaller Engines Supplying Modest
Electrical Power
Expendable TLI Stagefor First Lunar Outpost
Mission using Clustered 25 klbf Engines --
Fast Track Study (1992)
Reusable Mars Transfer Vehicle usingSingle
75 klbf Engine -- SEI (1990-91)
Reusable Lunar Transfer Vehicle using Single 75
klbf Engine -- SEI (1990-91)
Artificial Gravity BNTR Crewed Transfer Vehicle
also using Clustered 15 klbf / 25 kWe Engines
-- Mars DRM 4.0 (1999)
Bimodal NTR Earth Return Vehicle using
Clustered 15 klbf / 25 kWe Engines -- Mars DRM
1.0 (1993)
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Fully Reusable NTR Lunar Transfer Vehicle
(90-Day Study / SEI 1989-91)
IMLEO 218 t Burn Durations - TLI 30.4
mins - LOC 7.5 mins - TEI 4.5 mins -
EOC 9.8 mins Total 52.2 mins
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Modular Moon / Mars NTR Transfer Vehicle Concept
HLLV Lift Capability / PL Envelope 150 t / 10
m (dia.) x 30 m length(SEI Lunar and Synthesis
Report Split Cargo and Crew Mars Architectures --
1990 -91)
Source Borowski et al., AIAA-93-4170,
NASA TM -- 107071 (1993)
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Trajectory Options Considered

• Opposition-Class Mission Characteristics(Used in
  90-Day / SEI Mars Studies)
• Short Mars stay times (typically 30 - 60 days)
• Relatively short round-trip times (400 - 650
  days)
• Missions always have one short transit leg
  (eitheroutbound or inbound) and one long transit
  leg
• Long transit legs typically include a Venus
  swingby and a closer approach to the Sun ( 0.7
  AU or less)
• This class trajectory has higher DV requirements
  

Outbound Surface Stay Inbound

• Fast-Conjunction Class Mission Characteristics
  (Used in DRM 4.0 /DRA 5.0)
• Long Mars stay times (500 days or more)
• Long round trip times ( 900 days)
• Short in-space transit times ( 140 to 210 days
  each way)
• Closest approach to the Sun is 1 AU
• This class trajectory has more modestDV
  requirements than opposition missions

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90-Day Study Chemical / Aerobrake Mars
TransferVehicle (MTV) Concept and Mass Breakdown
2016 Opposition-class missionwith in-bound Venus
swingby 434-day round trip with 4 crew and
30-day stay at Mars Elliptical parking Mars
orbit(250 km x 33,793 km 24hr orbit) 25 t of
cargo to the surface Expendable MTV
capsule return of crew to Earth
Four 200 klbf LOX/LH2 engines with Isp 475 s and
? 4001 Expendable trans-Mars injection stage
has 90 propellant mass fraction
Source Boeing, Space Transportation Concepts
Analyses for Exploration Missions (STCAEM) study
contract with MSFC (1990-1993)
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All Up NTR Mars Transfer Vehicle for 2016
Opposition-class Mission

434 Day Round Trip / 30 Day Stay at Mars / IMLEO
668 t / Reusable


Source Borowski, 90 Day Study / SEI -- 1990-91
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Initial Mass in LEO (IMLEO) Requirements for Mars
Opposition-class Short Stay-Time Missions
NTR reduces IMLEO by 50 compared to chemical
/aerobrake and 200-300 compared to all
chemical also flattens IMLEO Variance /
Sensitivity across Mission Opportunities
500-Day Constraint relaxedto 700 days (30 day
stay)
(Isp 475 s)
(Isp 475 s)
(Isp 925 s)
For all chemical system, gt 85 of mission mass
is propellant. Assuming launch costs of 5-10
k/kg for a future heavy lift vehicle, the
propellant delivery costs for a single Mars
mission alone could pay for the entire NTR
development program
Source NASAs Office of Aeronautics, Exploration
and Technology, presented to
Stafford Synthesis Team in 1991
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Small NTR Engine Designs Can Provide
Multi-Mission Use-- Robotic Science, Cargo
Crewed Moon/Mars/NEA Missions --
Small NTR can provide high thrust and Isp (2 x
LOX/LH2 ), plus stage electrical power. Small
size compatible with existing chemical rocket
hardware time and cost to develop, ground test
and fly is reduced (ATP 10 yrs) compared to
larger engines
10-25 kWe Brayton Unit (GRC vacuum tested a 10
kWe unit for 38,000 hours during 1970s)
Radiation Shield
10.5 m(34.4 ft)
Twin RL-60 LH2 turbopumps
Compact Engine Reactor Core
5.36 m(17.6 ft)
RegenerativeNozzle
RL10B-2Radiation-cooled Skirt
15 klbf / 25 kWe Bimodal NTR Engine
Size of 1972 Vintage 75 klbf NERVA Engine
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Bimodal NTR Cargo Crew Transfer Vehiclesused
for Long Surface Stay Mars DRM 4.0 -- 1999
6 - 80 t SDHLVs plus Shuttle for Crew
TransHab Delivery
2011 Cargo Mission 1 Habitat Lander IMLEO 131.0
t
2011 Cargo Mission 2 Cargo Lander IMLEO 133.7 t
Optional In-Line LH2 Tank (if needed)
2014 Piloted Mission Artificial Gravity Crew
Transfer Vehicle IMLEO 166.4 t
Total Mission Time 900 days(6-7 month 1-way
transits and 500 days on surface of Mars)
? IMLEO 431 t
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Artificial Gravity Bimodal NTR Crew Transfer
Vehicle (CTV) for Mars DRM 4.0 (1999)
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DRM Triconic Aerocapture / Descent Shell is
Significant Scale-up from Demonstrated /
Planned AB Systems
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DRM 4.0 to DRA 5.0 Trace Analysis Results for
Cargo Crewed Mars Transfer Vehicles(Ref S.
K.Borowski, Mars DRM 4.0 to 5.0 Trace Analysis,
Oct. 2007)
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Mars Design Reference Architecture 5.0 Mission
Profile (Phase II NTR Twin Drop Tank Option
Shown)
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In-Situ propellant production for MAV
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Other Candidate NTR / BNTR Missions

• Technology Demonstrator / Robotic Precursor
  (Thrust Size 15 klbf)
• - Subscale Mars cargo mission with
  triconic aerobraked surface payload
• element (e.g., pressurized rover). Tests
  NTR/BNTR, triconic aerobrake flight
• maneuverability and simulates dual launch
  Earth orbit rendezvous and dock
• of TMI stage and aerobraked payload in
  subsequent human Mars missions
• - High energy injection stage for outer
  planet payload (Single 20-22 t EELV)
• 2. Lunar Base Buildup (15 - 25 klbf single
  or clustered engines)
• - Use to pre-deploy / deliver higher
  capacity cargo landers to lunar orbit to
  support base buildup
• 2a. Mars Dress Rehearsal Mission in Lunar Orbit
  Use clustered engine Mars transfer vehicles in
  simulation of the Mars mission (e.g., time in
  lunar orbit similar to Mars mission) in lunar
  orbit as recommended in the Synthesis Report
• 3. 1-Year Round Trip Near Earth Asteroid (NEA)
  Mission (clustered engines)
• - Dress-rehearsal mission in deep space
  of piloted Mars transfer vehicle (MTV) its
  systems propulsion, power, life support,
  artificial gravity operations

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Example Proposed Mars Flight Demonstrator -
BNTR-powered Triconic Aerobrake Mission -

• Elements
• - 15 klbf / 10 kWe BNTR stage
• - Triconic aerobrake
• Description
• - Uses two 20-22 t Delta IV-H launches
• - Earth orbit rendezvous and dock
• Science Objectives
• - Establish infrastructure for surface science
  capability
• - Extended sorties, deep drilling, sample
  analysis
• Exploration Objectives
• - Subscale validation of HMM cargo flight
• - Validate key transportation system elements
• - Deliver ISRU, power, rover demo units
• Technical Approach
• - Use BNTR stage for TMI and in-space power

Total Mass (kg)
33,000 15 klbf NTR 2225 10 kWe Brayton
210 Dry TMI Stage 6260 LH2 Prop
12130 RCS Prop 250 21,075 Triconic
Aerobrake (20) 2385 Descent Prop (632 m/s
?V) 1500 Lander System 1900 Net Surface
Payload 6140 11,925

Large payload consistent with pressurized rover
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Reusable BNTR Artificial Gravity Asteroid Survey
Mission
(4 - 80 t HLLVs to launch ASV elements, TransHab
twin ManCans CEV launch)
IMLEO 259 t
Asteroid departure 10/7/2027 ?V 0.612 km/s
Earth Orbit
?
Near Earth Asteroid Orbit
Earth return to 500 km x 71,136 km HEEO
5/14/2028 ?V 1.711 km/s
Asteroid arrival 9/7/2027 ?V 0.851 km/s
Earth departure from 407 km circular orbit
5/18/2027 ?V 4.014 km/s
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Deep Impact Mission to Comet Tempel 1 (2005)
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Primer on Near Earth Object (NEO) Impact Hazards
NEOs are small objects with orbits that
regularly bring them close to Earth could
potentially pose an impact threat to Earth
includes asteroids (NEAs) ?3000 kg/m3),
short-period (SPCs ?2000 kg/m3) and long-period
comets (LPCs ?2000 kg/m3) Stony NEAs and
SPCs typically hit Earth with impact velocities
(Vi) of 20 km/s. For LPCs, the range of impact
velocities is 45-60 km/s Earths atmosphere
protects us from smaller NEOs (40 m DNEA, IKE
4.8 MT of TNT) With DNEA 50 m - 1 km, IKE
9.35 - 7.5 x 104 MT of TNT and can do
tremendous damage to land areas ranging from
103s km2 to the size of small-to-moderate
states In 1908, a stony meteoroid of 50 m D
exploded in the air above the Tunguska river
in Siberia with the air blast devastating a large
area of unpopulated forest The K/T event was a
globally catastrophic impact which wiped out the
dinosaurs 65 million yrs ago. It was caused
by an 11 km D asteroid (IKE 108 MT of TNT) that
excavated the 200 km D Chicxulub crater in
Mexico For deflection of large (1 km D) NEOs
on final approach, a high energy yield nuclear
payload (1 kT/kg) appears to be the most viable
approach. Delivery on a high velocity
intercept stage can also help maximize the
intercept range and deflection time

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Assumes 20 t PL 130 t Ares-V lift capability
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Benefits of NTP for Exploration NEO Intercept
Missions

• NTR engines have negligible radioactivity at
  launch / simplifies handling and stage processing
  activities at KSC -- Shortens prep launch times
  
• High thrust / Isp NTR uses same technologies
  as chemical rockets, (e.g., Ares-V core stage
  uses a 10 m D, 44.5 m L Al/Li LH2 tank
  sufficient for 2 cargo or 1 crewed NTR MTV)
• Short burn durations (lt 60 mins) rapid LEO
  departure acceleration to intercept velocity
  (Vi)
• Less propellant mass than all chemical
  implies fewer ETO launches (e.g., Ares-V, D-IV)
• NTR engines can also be configured for
  bimodal operation (propulsion and electric
  power generation) also for bipropellant
  operation (e.g., LANTR NTR with LOX
  afterburner nozzle)
• For HMM, NTP has fewest mission elements,
  much simpler space operations than alternatives
• For NEO intercept, NTP achieves higher Vi
  than chemical for given payload and LEO launch
  mass allows a viable response capability even
  when the detection range (RD) is small (1 AU or
  less) and response times are short may be the
  only option available to deflect high velocity
  LPCs if RD is limited to 4 AU from Earth
• Small engines (15-25 klbf) can be used
  individually or in clusters to maximize mission
  versatility -- for robotic science, human Moon,
  Mars and NEO exploration / intercept
• NTP can be developed in 10 years after ATP.
  Small engine size could be key to reducing time,
  cost to develop, ground test and fly