1. An Earth – Moon Transportation System Patrick Zeitouni Space Technology

2. Overview  Address the Earth-Moon transportation architecture, sometimes referred to as “mode”  Outline –Introduction –Impacts & importance –Possible Modes –Proposed Mode ­Description ­Performance –Summary –Backup & References

3. Introduction  Topic of great importance in Apollo Era –Allowed the US to achieve the 1 st lunar landing by 1969 –Enabling the Apollo 13 rescue  Several mode options exist, outlined in the next slides  Looking forward –Not “Flag & Footsteps” mission. This time we’re here to stay –Initial missions will lead to a lunar base, which feed into an eventual Mars mission  Mode selection has many impacts –Initial launch mass & frequency –Sustainability of lunar program at stake (Cost, Private sector involvement) –Mission Flexibility & Complexity –Safety, abort availability –Payload weight growth Initial Human Landing on Mars

4. Possible Modes  Direct ascent –Earth entry module taken to lunar surface & back  Earth orbit rendezvous (EOR) –Same as above, except initial mass is brought up by several launches & rendezvoused in Earth orbit (e.g. at ISS)  Lunar orbit rendezvous (LOR) –Separate lander to/from lunar surface, rendezvous in lunar orbit, Apollo method of getting to the moon  Lunar surface rendezvous (LSR) –Lander & Earth return module rendezvous on surface Direct Ascent Direct Ascent Examples EOR LOR

5. Proposed Hybrid Mode  LOR/LSR hybrid with a station at L1  Example Mission –Day 1: Crew leave Earth in Crew Transport Vehicle (CTV) –Day 4: CTV Rendezvous at L1 with station. Crew transfers to Lunar Transfer Vehicle (LTV) and undocks –Day 5: LTV reaches Lunar orbit/surface –Landing -5 days: Crew leaves Lunar surface in LTV –Landing -4 days: Crew arrives at L1, transfers to CTV –Landing -0 days: CTV reenters Earth atmosphere  Cargo, Lunar Base and L1 station sent separately using low energy/longer orbits –Rendezvous at L1 (e.g. unmanned LTV) or Lunar surface (e.g. Lunar Base) CTV L1 Station LTV LEO (300 km) Lunar Orbit (100 km) 30 min 1 day 4 days 15 min Lunar Base

6. Hybrid Mode Component Description  Crew Transport Vehicle (CTV) –Apollo CSM-like spacecraft –Launched on MLV (45,000 Kg to orbit) Boeing Proposed CTV  L1 station –Simple station, built on a familiar chassis like the Russian DOS-17K. –Not manned for the most part, primary purpose is hanger for untended LTV & CTV –High ISP low thrust electric propulsion for Stationkeeping in the unstable L1 point (.3 km/s dV req. annually) ATK SRB with CTV Example L1 Station with Docked CTV

7. Hybrid Mode Component Description  Lunar Transfer Vehicle (LTV) –Lander launched with CTV (requires HLV) or separate (requires MLV) –Lunar “crasher” stage, decelerates LTV and then separates & crashes into surface. Rest of LTV is one stage (Design borrows from Soviet manned lunar designs).  Cargo Transfer –Delivered to LEO by Shuttle derived HLV –Delivery to L1 & Lunar orbit by high ISP system –Unmanned Lunar truck (derived from LTV) delivers cargo from lunar orbit to surface LTV Shuttle Derived HLV Crasher Stage Lunar Truck

8. Hybrid Mode Benefits  Lunar surface accessibility –From L1 point, all lunar surface 1 day flight away Skylab-like L1 Station with attached CTV Apollo Landing Sites  L1 Station provides parking & stationkeeping –Extra LTV for aborts –CTV for extended stay lunar astronauts –Ability to store CTV in Cislunar space for long duration was something missing from the Apollo missions, requiring an extra trip back & forth

9. Hybrid Mode Benefits  As human payload grows, more frequent CTV trips are made, and eventually a reusable/lifting body CTV is introduced.  As cargo payload grows, impacts to crew transportation minimal. More HLV launched or more efficient in-space propulsion used.  L1 useful for Mars missions –Low energy transfer trajectory to Mars –Models interplanetary space conditions better than LEO for equipment checkout  Private sector involvement: –Cargo transport to L1 & lunar orbit/surface –Fuel for LTV at L1 or in-situ on the lunar surface Human Mission to Mars

10. Hybrid Mode Benefits: Abort Modes  Abort during launch –Apollo-type escape tower  Abort during LEO to L1 –Take refuge at L1 –CTV reenters in 7 days (max) –LTV (at L1) used as rescue vehicle  Abort during L1 to Lunar Orbit –LTV returns to L1 in 2 days (max) –Extra LTV at L1 station used as rescue vehicle  Effectively has two free-return trajectories with 3 safe havens (Earth, L1 Station, Lunar Base) Earth Moon L1 3.5 Days 1 Day Abort to L1, Abort to Earth Abort to L1, Abort to Surface Boeing Proposed LES Apollo LES Test

11. Hybrid Mode Disadvantages  Requires a station at L1 (Launch, resupply, maintenance)  Imposes a higher dV requirement on the LTV, causing it to be heavier than the Apollo LM  Several rendezvous necessary to complete mission  If a crippling explosion were to happen during one of the coast phases, the crew may not have a second spacecraft (like the LM in Apollo 13) for an immediate evacuation

12. Results Summary  Combines simplicity of direct ascent with mass savings of rendezvous  Mission can be though of as a “Direct Descent” from L1  Rendezvous at L1 mission enabler –Lower launch mass & required # of launches –Mission flexibility –Good abort coverage without high complexity –Allows for mass growth due to crew/mass separation (especially when combined with surface rendezvous)

13. References  NASA images: http://spaceflight.nasa.gov/gallery/images/vision/index.htmlhttp://spaceflight.nasa.gov/gallery/images/vision/index.html  Boeing images: http://boeingmedia.com/images/index.cfmhttp://boeingmedia.com/images/index.cfm  Other images: http://www.astronautix.comhttp://www.astronautix.com  Delta Velocity requirements: The Lunar Base Handbook – Peter Eckart

14. Backup Slides

15. Mass & dV Budget  CTV (CM+SM) smaller that Apollo CSM because of the smaller delta V requirements  Conversely, the LTV bigger than Apollo because of the larger dV requirements Mass in Kg

16. Lagrange Point #1  Lagrange points are solutions to 3 body equations of motion –A body at an L point will feel a net zero force –Balances gravity from Earth, gravity from moon, and centrifugal force of body revolving around Earth  These points are gateways for minimum energy transfers to moon, Earth, and interplanetary orbits  L1, L2 & L3 points are unstable, requiring ~260 m/s annual stationkeeping Earth L1MoonL2 L5 L4 L3