Scenario 1

1
Scenario 1

• Using an NTR to Complement the ESAS Mission

Presented by Paul Cummings
2
ESAS Architecture Overview
20 - 21 mTDelivery
Lunar Surface Access Module (LSAM)
Low Lunar Orbit (LLO)
Trans-Lunar Injection (TLI)
Earth Departure Stage (EDS)
Low Earth Orbit (LEO)
Cargo Launch Vehicle (CaLV)
NASAs Exploration Systems Architecture Study
Final Report. NASA-TM-2005-214062, November 2005
3
ESAS Architecture Overview
LEO
EDS Detaches from CaLV Burns to Circularize
Orbit Achieve LEO
LSAM Burns to Achieve LLO
Launch on CaLV
LSAM Burns to Descend to Lunar Surface
Earth
Moon
Earth
LSAM Lands
EDS Burns to Achieve TLI
LLO
TLI
LSAM Detaches from EDS
NOT TO SCALE
NASAs Exploration Systems Architecture Study
Final Report. NASA-TM-2005-214062, November 2005
4
ESAS Architecture Parameters

• Delta Vs
• LEO-TLI
• 3140 m/s
• Provided by EDS
• TLI-LLO
• 855 m/s
• Provided by LSAM
• LLO-Lunar Surface
• 1911 m/s
• Provided by LSAM

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ESAS Architecture Components

• CaLV
• Two 5-segment Hydroxyl-Terminated Polybutadiene
  (HTPB) Reusable Solid Rocket Motors (RSRMs)
• Large central LOX/LH2 powered core vehicle with
  five RS-25 Space Shuttle Main Engines (SSMEs)
• Gross Liftoff Mass of 6.4 Mlbm
• Deliverables
• 54.6 mT to TLI
• 124.6 mT to LEO at 28.5º

NASAs Exploration Systems Architecture Study
Final Report. NASA-TM-2005-214062, November 2005
6
ESAS Architecture Components

• EDS
• Purpose
• Provide Final Impulse into LEO
• Circularizes LSAM at 160 nmi orbit
• Accelerates LSAM into TLI
• 501,000 lbm at Launch
• LOX/LH2 Propellant
• One Block II J-2X Engine

NASA-TM-2005-214062, November 2005ESAS Update
Accelerating Lunar Missions. February 2006.
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ESAS Architecture Components

• Heavy LSAM
• Purpose
• Provide Braking into LLO
• Cargo Descent to Lunar Surface
• Cargo Pallets Replace Habitation Modules
• Development to Commence in 2011

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ESAS Architecture Summary

• Performance per CaLV launch
• Deliver a payload of 21 metric tons to the lunar
  surface
• Put 55 metric tons into TLI
• 125 metric ton IMLEO

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Mission Goals

• Define a series of mission goals to place 50-150
  metric tons of cargo on the surface of the Moon
• Compare the performance of the standard ESAS
  architecture and an NTR-supplemented ESAS
  architecture

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NTR-Based ESAS Architecture

• Proposed Architecture Changes
• Replace EDS with an NTR-propelled transfer stage
• Use transfer stage to brake into LLO from TLI
  (rather than using LSAM)

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NTR-Based ESAS Architecture

• NTR Safe Storage
• Once the NTR has been used to place the LSAM in
  LLO, it needs to be stored safely
• It cannot be left in LLO perturbations result in
  a short orbital lifetime for objects in LLO
• It cannot be allowed to return to LEO this would
  be perceived publicly as too great of a safety
  risk
• It will therefore be placed in high lunar orbit
  (1000 km altitude) after use

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NTR-Based ESAS Architecture
LEO
NTR Burns to Enter Parking Orbit in HLO
NTR Burns to Achieve LLO
NTR Burns to Achieve HLO
Launch on CaLV
NTR Disengages from CaLV Burns to Circularize
Orbit and Achieve LEO
Earth
Moon
Earth
LSAM Burns to Descend to Lunar Surface
NTR Burns to Achieve TLI
LSAM Lands
LLO
HLO
TLI
NOT TO SCALE
NASAs Exploration Systems Architecture Study
Final Report. NASA-TM-2005-214062, November 2005
13
NTR-Based ESAS Architecture
EDS
NTR
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NTR-Based ESAS Architecture

• Mission Design Changes
• NTR substituted for EDS
• Option 1 Using the same IMLEO as the ESAS
  architecture, more payload can be placed on the
  lunar surface with an NTR-propelled transfer
  stage
• Option 2 Alternatively, the same payload can be
  placed on the lunar surface with a significantly
  reduced IMLEO by replacing the EDS with an
  NTR-powered transfer stage (due to the
  significantly higher Isp of the NTR system)

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NTR-Based ESAS Architecture

• Option 2 is difficult when considering direct
  ESAS substitution
• CaLV launches are discretized
• Launching less than a full payload would not
  significantly reduce launch costs
• Cannot launch half of a CaLV
• Therefore, Option 1 will be considered first

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NTR-Based ESAS Architecture

• Assumed NTR Parameters
• Isp 850 seconds
• Exhaust Velocity 8339 m/s
• Thrust 150 kN
• Mass of Engine Shield 6.4 mT
• NTR will perform 4 burns
• Achieve LEO 71 m/s
• LEO-TLI 3140 m/s
• TLI-LLO 855 m/s
• LLO-HLO 292 m/s

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NTR-Based ESAS Architecture

• Assumptions (continued)
• LSAM stage was scaled from ESAS design
  assumptions
• LSAM requires less propellant because it does not
  perform the TLI-LLO burn
• Isp 433 s
• Exhaust Velocity 4248 m/s
• Recall that we are assuming an MLEO of 125 metric
  tons

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NTR-Based ESAS Architecture

• Engine and Shield Masses
• Engine mass was determined by modeling an
  effective core using the code MCNP
• Shield mass was also determined by modeling the
  dose transmitted to the payload using the code
  MCNP

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NTR-Based ESAS Architecture
MCNP Model 2D Renderings
Outer Pressure Vessel
Model parameters (densities and physical
dimensions) were used to determine engine and
shield masses.
LH2 Fuel Tank
Inner Pressure Vessel
Turbopumps
Radiation Shield
Core
Engine
Control Drums
Nozzle
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NTR-Based ESAS Architecture
MCNP Model 3D Renderings
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NTR-Based ESAS Architecture
MCNP Model 3D Renderings
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NTR-Based ESAS Architecture

• NTR Transfer Stage Design
• For the NTR, engine mass is a significant portion
  of overall mass
• Engine mass is treated as a portion of payload
  mass
• Engine mass is not included in structure mass
• Tank mass is calculated separately and is not
  included in structure mass

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NTR-Based ESAS Architecture

• NTR Transfer Stage Design
• The NTR uses pure LH2 for propellant LH2 tanks
  tend to weigh 15 of the propellant mass
• Tankage Fraction .15
• Structure mass (excluding tanks and
  engine/shield) is assumed to be 2 of overall
  mass
• Structure Fraction .02
• The NTR will need to produce a total delta V of
  4358 m/s

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NTR-Based ESAS Architecture

• NTR Transfer Stage Design
• Transfer Stage Masses
• Propellant Mass 50881 kg
• Tank Mass 7632 kg
• Structure Mass (excluding tanks/engine) 2500 kg
• Mass of payloadengine 63987 kg
• Engine (with Shield) Mass 6400 kg
• LLO Payload Mass 57587 kg

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NTR-Based ESAS Architecture

• LSAM Descent Stage Design
• Scaling from the published ESAS architecture, the
  structure mass of the LSAM, including the mass of
  the engine and fuel tanks, is 14 of the total
  mass
• Structure Fraction .14
• The LSAM will need to produce a delta V of 1911
  m/s

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NTR-Based ESAS Architecture

• LSAM Descent Stage Design
• Descent Stage Masses
• Fuel Mass 20864 kg
• Structure Mass 5907 kg
• Lunar Surface Payload Mass 28661 kg

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NTR-Based ESAS Architecture

• Performance per CaLV launch with NTR
  augmentation, Option 1
• Deliver a payload of 28.6 metric tons to the
  lunar surface (36.2 more than a chemical EDS)
• Put 57.9 metric tons into LLO
• 125 metric ton IMLEO

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NTR-Based ESAS Architecture

• Achieving Mission Goals

NTR-Based CaLV Launches
Putting 50 metric tons on the Lunar Surface
Standard CaLV Launches
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NTR-Based ESAS Architecture

• Achieving Mission Goals

NTR-Based CaLV Launches
Putting 100 metric tons on the Lunar Surface
Standard CaLV Launches
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NTR-Based ESAS Architecture

• Achieving Mission Goals

NTR-Based CaLV Launches
Putting 150 metric tons on the Lunar Surface
Standard CaLV Launches
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NTR-Based ESAS Architecture
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NTR-Based ESAS Architecture

• What if the CaLV could be redesigned?
• Reducing IMLEO placing the same payload on the
  lunar surface becomes an option
• Reducing IMLEO would result not only in decreased
  launch costs, but in decreased development costs
  as well
• Option 2 could be considered

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NTR-Based ESAS Architecture

• Option 2 Mission Design
• LSAM Descent Stage Design
• Descent Stage Masses
• Fuel Mass 15287 kg
• Structure Mass 5907 kg
• Lunar Surface Payload Mass 21000 kg
• Total Mass 42194 kg

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NTR-Based ESAS Architecture

• Option 2 Mission Design
• Transfer Stage Masses
• Propellant Mass 38641 kg
• Tank Mass 5796 kg
• Structure Mass (excluding tanks/engine) 1899 kg
• Mass of payloadengine 48594 kg
• Engine (with Shield) Mass 6400 kg
• LLO Payload Mass 42194 kg
• Total Mass 94930 kg

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NTR-Based ESAS Architecture

• Performance per CaLV launch with NTR
  augmentation, Option 2
• Deliver a payload of 21 metric tons to the lunar
  surface
• Put 42.2 metric tons into LLO
• 94.9 metric ton IMLEO
• By replacing the chemical EDS with an NTR-based
  transfer stage, IMLEO is reduced by 24.1

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Conclusions

• Using an NTR to augment the ESAS mission can
  improve performance in one of two ways
• By using the CaLV as is, lunar surface payload
  mass is increased by 36.2, from 21 mT to 28.6
  mT, without increasing IMLEO
• By redesigning the CaLV to take advantage of the
  NTRs performance, IMLEO can be reduced by 24.1,
  from 125 mT to 94.9 mT, without losing any lunar
  surface payload mass