Presentation Transcript

1. Designing an Enduring Mars CampaignFuture In-Space Operations (FISO) Working GroupTeleconPresentationSept 14, 2011

   Gordon Woodcock Huntsville Alabama
2. Historical Note In the 1960s, Wernher Von Braun had a well thought-out overall approach to space exploration, sometimes known as the von Braun paradigm: Develop a re-usable rocket for launch to orbit. He thought expendables would be too expensive to fly, a forward-thinking idea that most of the space community still has not adopted more than a half-century later. Build a space station in Earth orbit. Use the space station, among many applications, as a launch platform for exploration missions beyond low Earth orbit. Visit and explore the Moon. Go to Mars and explore. The “space race” with the Russians caused the U.S. to skip steps 1, 2, and 3, and execute part of 4(visit). High operating cost for the heavy-lift expendable architecture resulted in our abandoning lunar exploration after six visits. We seem to be fixated on this very expensive way of doing human exploration. It wasn’t sustainable then and it isn’t now. We need an enduring approach.
3. Objectives Destinations for human exploration are often cited as goals; real goals are rarely mentioned. Destinations are not goals. Goals for human space exploration should be practical benefits for civilization. The most plausible are knowledge and economic growth. Human progress has always been tied to economic growth. Growth cannot continue indefinitely on a finite planet; it requires room to grow. Phrases such as “extended human presence” on the Moon or elsewhere recognize this as a long-range goal without stating it. Humans to Mars, therefore, has two main rationales: Scientific exploration beyond what is practical with robotic missions, Development of knowledge and technology leading to permanent human presence and eventually settlement.
4. The Challenge: Design for Affordability Analyze a series of Mars missions, representing incremental development of Mars exploration capability: Assess potential for reaching goals. Electric propulsion cargo and propellant transport with propellant depots at destinations to minimize launch mass without accepting excessive human mission durations: Reduce launch cost. Make in-space transportation re-usable … initial operations expendable where necessary but evolve to reusable: Reduce in-space transportation operating cost. Vehicles are multi-purpose building blocks, not tailored to specific purposes, so that as purposes multiply, the number of vehicle types in the stable does not: Reduce development cost. Design for launchers that have other customers … launch capability of 40 t. with 6.5-meter diameter fairing was used to size systems and develop mission manifests: Reduce development cost and increase launch rate. Provide propellant depots at destinations with support capabilities including human habitats: Improve efficiency, reliability and safety. Aim for eventual self-sufficient permanent presence: Without this, benefits are likely to be lacking or very limited.
5. Affordable Exploration Transportation The path to affordable transportation emulates mountain climbers. Establish camps in key (high-energy) locations, stock with supplies (mainly propellant), fly from camp to camp to destinations and return with small re-usable vehicles, refueling en route. Resource Base: Lunar Surface X Camp 1: L1 The Moon, and later Mars, will become resource bases, greatly improving supply logistics. Resource Base: Mars Surface Base Camp: LEO Camp 2: Elliptic Mars Polar Orbit Electric propulsion freighters become the propellant and cargo carriers of choice in view of their very low propellant consumption.
6. A Mission Set Delivery of a Mars polar orbit depot (MOD) that serves as a safe haven, propellant depot, and operations base at Mars. 2024 (Note: MOD on Phobos is an alternative.) Robotic Mars cargo landing: (a) deliver infrastructure and equipment for first crew mission, (b) certify lander for safe landing on Mars. 2026. “Short-stay” (opposition-class, Venus swingby) human landing mission, surface stay up to 20 days, depending on condition of cargo delivered on the first landing. 2028. Additional cargo deliveries, totaling about 100 t., in preparation for the first long-stay mission. 2030/2031. First “long-stay” (conjunction-class) crew mission. 2033. Long-stay missions are similar for all Mars opportunities. Unlike short-stay missions, propulsion requirements vary little from one Mars opportunity to another. A semi-cycler mission that enables crews to stay an entire Mars synodic period (26 months) so that time the outpost is not occupied is only a few days. Analyzed for 2028 opportunity because it’s a moderately difficult year, not practical for all high-thrust propulsion.
7. Preliminary “Below” use newer fig Propellant Depot Habitat 500 kWe SEP Tug with Tanker Lander Node MOD Solar Array
8. Where? Mars 48-Hour Orbit, Periapsis at S. Polewith Typical Arrival & Departure Vectors This sketch is to scale, with Mars’ axis tilted 24.5 degrees. Parking orbit periapsis is at the pole. With 90 degree inclination there is no nodal regression. Apsidal advance 0.265 deg/day needs to be nulled, requir-ing about 1.25 m/s per day. The orbit plane needs to be rotated around its major axis to align with arrival and departure vectors,usually near the ecliptic plane. This can be done with electric propulsion at apoapse, where the orbit velocity is about 287 m/s. These corrections are readily made by electric propulsion.
9. Typical “Standard Orbit” Mars Departure Delta V Loss Analysis This graph is for Mars departure on the 2024 opposition mission with 30-day stay, assuming the orbit shown on the prior slide. Ideal delta V is 3.426 km/s impulsive in-plane p-p transfer. Delta V is relative to this and derived from integrated trajectories with in-plane transfer and apsidal rotation on departure burn. This shows that departing away from periapsis to minimize apsidal rotation is a lot better than departing near periapsis and having to do a lot of apsidal rotation.
10. Delta Vs with Periapsis Misalignment 48-Hour Mars Orbit Note that aerocapture must occur at periapsis to engage the atmosphere This shows in-plane capture or departure impulsive delta V versus angle from periapsis, for the 48-hour elliptic orbit, with no apsidal rotation.
11. Mars Orbit Depot Delivery(Credit: John Dankanich)
12. Mars Orbit Depot Delivery
13. MOD Launch Manifest
14. Cargo Manifest for First Cargo Landing
15. Lunar Crew Lander Internal Arrangement(Mars Lander Derived from This Concept) Similar to lunar lander concepts previously published by ULA: Compatible with launch in a 6-meter fairing two differences: Horizontal landing Two key differences: Reusable, includes crew and cargo landers with same basic airframe No main engine on the long axis.
16. Twin Landers with Habitat & Node Enables large or heavy payloads to be carried;(2) places payload close to the surface for convenient unloading and handling. The two landers can return to L1 yoked together, or the yoke structure can be removed on the Moon so that its members can be used there.
17. Mars Lander ConceptRe-usable operations fueled in orbit for landing and on Mars for ascent. Movable aero surfaces for pitch trim during aero descent. LOX-LH2 propulsion modules fore and aft for balance; attitude control by differential throttling. No gimbals. Engines 115 kN (26 klbf) each, throttling range 3:1 to 4:1. Cargo space Landed cargo can include built-in crew habitat; expendable and re-usable cargo landers Early crew: expendable crew ascent stage and lander Later crew: crew module, re-usable crew lander; this version must refuel on Mars due to delta V and need for thermal protection. Mars’ atmosphere is so tenuous that for ascent, the vehicle can simply fly “sideways”; doesn’t need engines in the tail.
18. Lander Model with Movable Tail Tail 30° Dihedral Tail 30° Dihedral plus 40° Pitch
19. Mars Entry & Landing TrajectoryFrom Elliptic 48-hour Orbit Entry Mass 65 t. Useful Descent Payload 32 t. Estimated Descent & Landing Delta V 1360 m/s
20. Mars Cargo Lander Profile TableFirst Landing
21. Long-Stay Crew Round Trip Mission Diagram This Mission Uses an Expendable Lander with Storable Ascent Stage, Separately Delivered to Mars Orbit Depot (MOD) Mars Surface Event 9 Lander lands on Mars. Ascent stage returns to MOD MOD Prior opportunity: 2 – EP Tugs deliver 2 tankers & TEI stage LEO to MOS. No aerocapture. Tugs return to L1 but too late for DSH & tankers. Lander delivered to MOD by aerocapture without cryo propellant; refuels w/prop del Event 1. 3 – RUS’s prop recov at L1. Event 5 Crew mission includes DSH, and CTV. DSH & TEI stage to L1 Event 3. CTV to L1 Event 9. Event 8 Event 1 + L1 Event 6 Lander loaded 22 t. cryo, boosted by RUS and self-propelled to L1. Arrives empty except storables Event 3 Event 2 LEO Lander, propellant, RUS’s equipment to LEO Launch Support for Event 1 Crew direct launch to L1 in CTV Event 7 Event 4 Event 10 Earth EP Tugs deliver Deep Space Haband 2 propellant tankers to L1 & return to LEO. 2 self-propelled RUSs to L1 for Event 8. EP Tugs, DSH, 2 tankers launched to LEO
22. Network Diagram Event 9 Crew Landing and Ascent Event 1 Prior opportunity: 2 – EP Tugs deliver 2 tankers & TEI stage LEO to MOS. No aero-capture. Tugs return to L1. Lander descent propellant Event 8 Crew mission from L1 to MOS & return to L1 TEI stage & TEI propellant Event 2 Launches to support Event 1 Event 10 Crew launch direct to L1 in CTV or CEV Event 3 EP Tugs deliver Deep Space Hab and 2 propellant tankers to L1 & return to LEO Event 7 4 launches to support Event 6 Event 4 Launches to support Event 3 Event 6 Lander deliv-ered LEO-L1 RUS boost & self-propelled Event 5 Lander delivered L1- MOS: RUS + aerocapture
23. Short-Stay Mission Launch Manifest
24. Mars Surface Cargo General Manifest
25. 2033 Optimized 500-Day Stay Min Energy 1 Month Earlier C3 14.84 Vhp 3.88 1 Month Later C3 9.49 Vhp 3.36 2 Months Later (Arr 3 Mo. Later) C3 20.1 Vhp 4.71
26. Supporting a Permanent Outpost A permanent outpost is visualized as continuously staffed by at least some personnel. Minimize risk of a breakdown not remedied disabling the outpost Maximize productivity, resource utilization and outpost growth/expansion Tend to local agriculture (in pressurized modules) and food production Long-stay missions typically stay at Mars about 500 days The repeat interval for Mars opportunities is about 780 days, so the outpost unoccupied time is roughly 280 days between missions. Long-stay missions can stay longer, up to 700 days, but cannot completely fill the gap. Options for continuous staffing: Use opposition-type Mars flybys (semi-cycler profile) to drop off and pick up crew; unoccupied time is a few days. This will require further trajectory work because these trajectories can require high energies unless mitigated by Venus gravity assists or electric propulsion. At least some crew members stay through the gap, total time on Mars roughly 1280 days (3.5 years. Minimize gaps and use advanced robots to fill in for crew during gap times. Long-term radiation exposure is a major concern. Exposure in transit to Mars Exposure for surface operations (Mars has very little natural shielding compared to Earth) We need scenario-building for continuous staffing to estimate minimum number of crew, amount of infrastructure, local resource utilization, division/amount of labor required, and robotics augmentation.
27. Timelines for Outpost Occupancy Earth Years Repeating Opposition Missions Repeating Opposition-Like (Semi-Cycler) Mars Flybys with Crew Dropoff & Pickup (Gaps are shown to designate crew change; actual gaps only a few days) Repeating Conjunction Missions (Dashed lines show stayover option) Repeating “Stretched” Conjunction Missions (Gaps are about 3 months)
28. 2028 EP Semi-Cycler Trajectory(This year chosen because it’s difficult for chemical propulsion)
29. EP Semi-Cycler Mission
30. Size Comparison Conventional Interplanetary Vehicle 500 kW SEP tug RUS
31. Cost Analysis Results Development of Heavy Lift Plus In-Space Systems Development of In-Space Systems Procurement of In-Space Systems
32. Conclusion A network architecture that uses propellant depots at destinations and electric propulsion vehicles (“tugs”) to provision them with propellant, supplies and equipment achieves two major cost savings: Elimination of a need for very large and expensive heavy lift vehicles, and Practical re-use of in-space transportation systems, including electric propulsion and habitats, eliminating acquisition cost for replacement hardware. Such a network architecture opens the way for further cost savings, for example, propellants from in-situ production on the Moon and Mars.