Trans. JSASS Aerospace Tech. Japan Vol. 10, No. ists28, pp. Tg_9-Tg_18, 2012 Topics

Concept and Technology of HTV-R: an Advanced Type of H-II Transfer Vehicle

By Yusuke SUZUKI and Takane IMADA

ISS Cargo Return Vehicle Research and Development Office, Japan Aerospace Exploration Agency ,Tsukuba, Japan

(Received June 27th, 2011)

The first and second H-II Transfer Vehicle (HTV) successfully completed their missions in Nov. 2009 and March 2011. Now, JAXA has the capability to upload lots of logistics to support human activities on the International Space Station (ISS). Between these HTV missions, JAXA established "ISS Cargo Return Vehicle Research and Development Office" as a new section to study a new spaceship concept. It is called "HTV-R" and an features improved type of HTV, which enables JAXA to recover various samples of experiments conducted on the ISS. HTV-R equips a new re-entry vehicle called as "HRV(HTV Return Vehicle)" for the enhanced function. Although most of the HTV-R mission does not differ from original HTVs, once the HRV separates from the HTV-R after completion of the de-orbit maneuver, the HRV will fly autonomously and conduct lifting reentry to the atmosphere with controlling the attitude and trajectory to the predefined splashdown point. Because HRV flight profile resembles that for the human returning flight, JAXA considers that the study for HTV-R is not that of a cargo recovery system but also as the pathfinder of human transport system.

Keywords: HTV, Re-entry, ISS

Acronyms uses HTVs operational heritage, resource, and interfaces (such as to the ISS, ground system, and launch vehicle). Figure 1 ECLSS :Environmental Control and Life Support System shows the overall mission concept HTV-R support system. FRGF : Flight Releasable Grapple Fixture The HTV-R is launched from Tanegashima Space Center by a GSE : Ground Support Equipment H-IIB launch vehicle. Like the original HTV, it can carry HTV : H-II Transfer Vehicle cargo to the ISS but also has a new cargo recovery ability HTV-R : HTV - Return (down mass up to 1.6 metric tons). For this purpose, a re-entry HRV : HTV Return Vehicle vehicle called HRV (HTV Return Vehicle) is installed in the ISS : International Space Station HTV-R, which will conduct controlled a re-entry flight and be IVA : Intravehicular Activity recovered in the Pacific Ocean. LEO : Low Earth Orbit Before separating the HRV, the HTV-R will use all the PCBM : Passive Common Berthing Mechanism flight operations developed for the HTV. The trajectories PLC : Pressurized Logistics Carrier toward the ISS are the same as those of the HTV and their UPLC : Un-pressurized Logistics Carrier safety has been verified in previous HTV reviews. Ensuring safety on the ISS requires considerable effort. JAXA want to 1. Introduction minimize the task in the HTV-R development. The second HTV successfully completed its cargo resupply mission to the ISS on March 30, 2011. The HTVs original operation sequence around the ISS went very well. There was no critical trouble during its 67 days in operation. HTV-2 delivered 5,300 kg of cargo, including two science racks, two orbital replacement units, water, and the consumables necessary for the crew living in the ISS. Two successful HTV operations have encouraged JAXA to start researching upcoming programs as a part of Japan's future space activity plan. This includes HTV-R, which is likely to be one of the most attractive for system engineers who are studying the feasibility of Japanese manned space flight.

2. HTV-R Concept and Target The HTV-R (H-II Transfer Vehicle - Return) vehicle concept study commenced as an enhanced type of the HTV. It Fig.1. Overall operation profile of HTV-R.

Copyright© 2012 by the Japan Society for Aeronautical and Space Sciences and ISTS. All rights reserved.

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JAXA has continued the concept study of HTV-R for more which consists of a pressurized section at the top and a service than two years. The first step involved prioritizing the mission module at the bottom is a conventional configuration in targets. Consequently, following two targets are highly human launch systems. The experience of HTV-R prioritized in the HTV-R development. development will become a useful reference for designing the human launch system especially for the structure and - To establish safe and confident return technology as a separation mechanics. pathfinder for a Japanese manned spaceship (3) Lift control during re-entry - To realize an infrastructure for returning utilization A modern manned re-entry vehicle should control its lift specimen and on-orbit replaceable units from the ISS during the re-entry flight, both to relieve G-force acting on crew and minimize the dispersion of the splashing area to The development schedule toward the first HTV-R flight is facilitate quick recovery. It is not mandatory technology as an now under study and based on the shortest development plan, unmanned re-entry vehicle for sample return but needed as a is expected to be ready in around the Japanese financial year means of demonstrating technology for manned re-entry. 2017. (4) Partially redundant system 2.1. Target (1) : Pathfinder for a manned spaceship Manned vehicles should have complete redundancies in Numerous technological challenges must be overcome to important subsystems to manage all possible failures and develop a manned transportation system between ground and eliminate any possibility to cause a catastrophic situation. orbit. Of these, the need to ensure safe and gentle re-entry However, conventional unmanned vehicles have limited technology is a key area and a major milestone in the redundancies in systems reflecting the need to balance development of the transportation system. HRV in the HTV-R mission success against weight/cost efficiency aspects. simulates a manned re-entry vehicle and the demonstration of HTV-R, like other unmanned vehicles, includes partially its re-entry is part of two major targets of the HTV-R redundant systems but must have the potential to become the program. base design for a manned system via functionally Figure 2 shows every step toward a manned spaceship. enhancement of each subsystem. JAXA has completed the first step by HTV and the HTV-R program will be the second. The latter requires HRV 2.2. Target (2): Sample return capability from the ISS development and the HRV will demonstrate the re-entry flight. To utilize the ISS as a space factory as much as possible, HRV has the following characteristics as a bridge to a manned users always want to obtain their samples from the spaceship. experimental instruments in the ISS, from which the annual downmass requirement is shown in Fig. 3. The requirement in 2011 looks set to become one-third of the 2010 level reflecting the Space Shuttle retirement drastically decreases not only the capability but also the requirement for downmass. Conversely, it could be said that if we had plenty of such capability, downmass requirement would considerably exceed current expectations. Based on our interviews with users of experimental equipment, they wish to obtain samples as quickly, frequently and in as raw a state as possible. Smaller sample packing is time-consuming, more troublesome, and reduces the value of the raw sample. The HTV-R program will be able to cooperate with other international partners to realize a frequent and quick sample return infrastructure from the ISS. Also, HTV-R will realize a complete cycle of JAXA's in-orbit experiments. JAXA is already capable of transporting Fig.2. Technology steps toward a manned spaceship1). experimental units to the ISS by HTV, but lacks the ability to obtain the outcome from them now. The second purpose of (1) Re-entry vehicle size is equivalent to manned system HTV-R is to obtain the sample return capability from the ISS HRV design (the trade-off study of which is shown in in order to complete a cycle of experiments utilized in the ISS. section 4) has a reasonable shape and size for a manned Figure 4 shows a few examples to recover from the ISS. vehicle. The size (diameter: 4.2m) is sufficient to transport 4 HTV-R flights will enable JAXA and Japanese space crew members to a LEO station and bring them back to Earth. scientists to utilize the Japanese module "Kibo" and the experimental equipment in it more efficiently. (2) Similar configuration The baseline rocket for the human launch system has yet to be determined. However the vehicle configuration of HTV-R

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2) Fig.3. Annual downmass requirement for the ISS .

Fig.5. Operation image (Option-0).

(2) Option-1 (Medium Re-entry Vehicle on HTV Pallet) After Option-0 was excluded, there were two options. Each option has a re-entry vehicle, which has a limited re-entry flight function in different aero shape size. Option-1, one of the candidates shown in Fig. 6, replaces the exposed pallet in the original HTV and modifies the un-pressurized carrier into the storage and injection bay for a re-entry vehicle.

Fig.4. Recovery cargo (examples).

3. Trade-off Study to Determine the HTV-R Configuration To satisfy the two targets in section 2, JAXA conducted a series of trade-off studies to determine the HTV-R configuration. Three types of re-entry capsule/vehicle integrated in different parts of HTV were investigated and following is a summary of the trade-off.

3.1. Candidates (1) Option-0 (Small Capsule in the HTV Carrier) This entry involves the re-entry capsule being installed into 3) the pressurized module of the HTV . The capsule will be Fig.6. Configuration (Option-1). jettisoned by air pressure in the pressurized module via the modified hatch, the width of which limits the capsule size. It The re-entry vehicle size is limited by the open area of the is difficult to equip sufficient system inside the small capsule un-pressurized carrier at less than 2.6 m (diameter) and 1.5 m to control its attitude and navigate the splashing point. This (height). It is equipped with propulsion, guidance, and a option was initially investigated to obtain samples incurring navigation system to conduct a controlled re-entry flight. But the least development cost. the limited size of the re-entry vehicle in Option-1 makes it Figure 5 shows an artist’s rendering of this option. As difficult to simulate the aero shape and volume of a manned shown here, almost all configuration of HTVs are not re-entry vehicle. modified from the original. The capsule size will be less than The HTV design, meanwhile, does not look drastically 0.5 cubic meters and the weight of the samples it contains will different from the original, although there are several peak at about 50 kg. development items for HTV modification. The interface This idea seemed appealing for sample return only but not between the exposed pallet and the un-pressurized carrier as a pathfinder for a human re-entry vehicle because it is too should be modified in this option and it also needs a new lacking mandatory functions for human return. pallet with new separation system. The new pallet has With this in mind, this option was excluded first in the separation mechanism not only with un-pressurized carrier but trade-off to determine the HTV-R configuration. also with the re-entry vehicle. These modifications lack relations with the manned system and add an undesirable point to this option. The interface

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mechanisms are completely different and will not be used in [Option2 (Big Re-entry Vehicle)] manned vehicle system. Most of the development items in Concept : Replace pressurized Carrier Option-1 will be used for HTV-R only. The situation is Re-entry Vehicle Mass : 6.5 ton (total) undesirable for JAXA since the total production number of Diameter : 4.2 m HTV-Rs is unknown. Height : 3.8m Downmass Capability: 1.6 ton [Option1 (medium re-entry vehicle)] Concept : Install re-entry vehicle on exposed pallet [Remarks] Re-entry Vehicle Mass : 2 tons (total) - Other modules except the pressurized carrier remain Diameter : 2.6 m unchanged from the original HTV Height : 1.5m - The rendezvous and capture operation is the same as Downmass Capability: 0.3 ton the current HTV - Same approach profile and corridor [Remarks] - Same capture box dimension - No flight function changes - Berthing and exposed pallet operation should be - Safety critical items: updated - Joint mechanics between HTV PLC and Re-entry - Longer overall length (about 0.8m) vehicle - Re-entry Vehicle Propulsion system - Minor difference in GNC - Leak, Explosion, Unintentional firing - Development items: - Forward RCS thrusters move to aft (about 0.7 – - New hatch 0.8m) - Separation system (PLC – Reentry Vehicle – - Mass properties (Total weight, Center of mass, and Pallet, Pallet – UPLC) Inertia) are within the prerequisite conditions for - Slide out system in pallet the original HTV - Other subsystems for a controlled re-entry vehicle - Minor difference in Power Supply System - Decrease the number of solar panels (3) Option-2 (Big Re-entry Vehicle Replaces Carrier) - Might be modified in the primary/secondary The final option is called Option-2 and is selected as the battery configuration baseline of the HTV-R design with numerous merits. JAXA selected this option in particular due to its advantages in terms 3.2. Trade-off result of similarities with a manned re-entry vehicle and its To satisfy the two main targets of the HTV-R shown in operation. Section 2, a larger re-entry vehicle is better to simulate a In this option, the re-entry vehicle is big and replaces the manned re-entry vehicle. The re-entry vehicle in Option-1 has pressurized carrier in the original HTV. Other modules in only a quarter of the volume of Option-2 as shown in Fig. 8. original HTV are not modified but a new short section is Of course, a larger vehicle raises different development installed between the re-entry vehicle and the other modules concerns. JAXA investigate all merits and demerits of each to equalize the load path. Figure 7 shows the overall vehicle option. concept in Option-2, in which yellow boxes identify the new development items. A considerable number of items will have 9 Similarities between HTV-R and the manned vehicle to be developed in this option but primarily for the purpose of manned re-entry vehicle development. 9 Re-entry vehicle development schedule and cost

9 Design modifications in the HTV

Fig.7. Vehicle configuration (Option-2).

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Fig.9. HTV-R vehicle and support systems.

(2) Interfaces Figure 10 is a cutaway image of the HTV-R. The un-pressurized section will be retained and it will have the capability to transport the exposed pallet with cargo as HTV Fig. 8. Pressurized sections and volume in Option-1 & 2. does now. The interfaces between HTV-R and H-IIB will be the same After the detailed survey of Option-1 and Option-2, JAXA as HTV. HTV-R will also retain its weight, inertia, and mass determined that Option-2 to be suitable as the HTV-R baseline, offset from the original HTV and use the avionics/propulsion for the following reasons: module unmodified in their structure. The interfaces between HTV-R and the ISS will also be - Many modifications were found in Option-1, most of identical thanks to the use of the same berthing system which were not usable for future vehicles (Passive Common Berthing Mechanism: PCBM). HTV-R has a grapple fixture (Flight Releasable Grapple Fixture: FRGF) - The re-entry vehicle in Option-2 can have a similar at the same location as HTV and the robotic system on the ISS aero shape to be the manned re-entry vehicle and the will be capable of capturing the HTV-R with the same design data will be useful for further development procedure that currently used for the HTV.

- Each modification in the HTV and the development items for the interface in Option-2 will become the basis for the design of the service module of the manned vehicle

4. Vehicle Design Study

4.1. HTV-R design The HTV-R will consist of five sections instead of the four sections in the original HTV.

(1) Construction Figure 9 shows the HTV-R vehicle construction with Fig.10. Modules in the HTV-R vehicle support systems. The HTV-R will use existing resources for HTV operation as much as possible in order to minimize the (3) HTV modification development cost. JAXA considers that new support systems Figure 11 compares side views of the HTV and HTV-R. will be HRV and its support system includes sea recovery The HTV-R will use the main structure of HTV and the operation. overall length of the former will be about 0.8m longer than HTV. However, the HRV will be conical in shape and be installed at the top cone section of the fairing of the launch vehicle, meaning the HTV-R will be able to use the same fairing for launch as the HTV without extension.

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Table 1. Previous re-entry vehicles in Japan.

Fig.11. Vehicle size of the HTV and HTV-R (2) Volume HRV shall comply with ISS safety requirements and has 2 HRV will have a pressurized section with a volume of 16 failure tolerances. Basically, the HRV will not activate its m3 (excluding internal components) and will probably prepare propulsion, pyrotechnic, and RF systems during proximity a volume exceeding 10 m3 for return sample loading. This size flight and when attached to the ISS. Accordingly, the HRV is sufficient as the baseline design for the manned vehicle design must have sufficient inhibits to prevent inadvertent when compared with other manned vehicles shown in Fig. 12. activation of these hazardous functions around the ISS to guarantee safety. From other perspectives such as mission success and further enhancement, HRV is designed to have redundancies in the avionics and propulsion systems, which have failure tolerance that differs from the ISS safety requirement.

4.2. HRV design (1) Functions for Re-entry flight Table 1 shows experimental re-entry vehicles developed in Japan, the experiences of which are used for designing the HRV. The Hayabusa capsule returned after 7 years inter-planetary flight, proving the exceptional heat load tolerance of its thermal protection material developed in Japan. However differences in vehicle configuration, size, and flight pattern should be taken into account when designing the HRV, which should be capable of demonstrating manned re-entry flight. As for the similarity with manned vehicles, only Hyflex (Hypersonic Flight Experiment) had guidance, navigation, and an actuator system to control the re-entry flight path, with other vehicles lacking any control methods to control attitude. Conventional manned vehicles control their attitude and flight path with thrusters. Since Hyflex used two moving 4),5),6),7) surfaces for its Pitch/Roll control, the algorithm differs from Fig.12. Total & habitable volume of manned vehicles . that of manned re-entry vehicles and HRV. JAXA must therefore develop an algorithm for HRV control and the first (3) Cargo service HRV will demonstrate human re-entry flight. There are plans to incorporate new cargo services in the HRV, such as electrical power and coolant loop, which will enable samples to be returned in temperature-controlled

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refrigerators. These services will also be extendable to the 5.2. On-orbit flight operation thermal control systems for manned vehicles in future. Figure 14 shows on-orbit flight operations of the HTV-R. All flight functions used in this phase are already retained in 5. Operation the current avionics module and propulsion module and are As mentioned in Section 2, the majority of the HTV-R independent from the HRV, hence the HTV-R will mission uses a profile identical to the original HTVs. rendezvous to the ISS using exactly the same method as the However some new procedures will be implemented to original HTV. To ensure ISS safety, all hazardous functions support HRV, the preparation of which will require details of such as the HRV propulsion system will be inhibited with cost and schedule. JAXA conducted a study of new operations sufficient redundancies during this phase. in order to determine a reasonable development plan including Once the HTV-R reaches the capturing point just below the these new support systems. ISS, it will be captured by the robotic arm in the ISS. These procedures were developed and verified with many tasks in 5.1. Launch site operation NASA/JAXA/CSA. JAXA is also attempting to retain this Every HTV module is transported from a different facility concept for the HTV-R and does not wish to modify and have in Japan, while HTV-R uses almost the same shipment to re-verify it. process. The only difference is that the pressurized carrier will be replaced by the adopter section and HRV, although the contractors for both of these new modules and the shipment route remain to be determined. Loading cargos onto the HRV will be easier than with the current pressurized carrier, since the HRV includes a side hatch for quick access during recovery operation on the ship, which can also be used for cargo loading at the launch site. Another particular feature of the HTV-R mission is the propellant loading process for HRV as shown in Fig.13. Since the HTV uses hazardous propellant, the loading process must be carefully controlled and operators must be protected with special suits. The third hazardous propellant for HRV will require the another loading operation and extend the total operation duration. To limit the time and cost, JAXA is investigating the possibility of a low toxic propellant, which could be loaded without evacuating other operators.

Fig.14. Flight operational flow.

5.3. HRV re-entry flight operation Figure 15 shows the final operations of the HTV-R up to the final de-orbit maneuver (the HTV-R conducts three maneuvers for de-orbit), the HRV will be separated and the distinctive operation starts as a re-entry vehicle. The HRV includes functions for controlled flight with an internal guidance system and thrusters. The HRV guidance system is equipped with all the required initialization functions for its attitude and location, while earth sensors or star trackers are used attitude determination. GPS receivers are also available for position sensing. The angle of attack of the HRV during the re-entry flight is determined by its center of mass offset. Thrusters on the HRV are used to Fig.13. Launch site operational flow. control the bank angle based on the navigation data generated

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in the HRV itself. The most important value for a re-entry vehicle is the Thermal protection materials around the HRV will guard all sidewall cone angle. 20 degree was selected as the angle and it functions in the vehicle during re-entry. A parachute system is very conventional value for a re-entry vehicle from LEO. will be deployed at around 10 km with the altitude data from IMUs or barometers. The positional accuracy of the parachute deployment is estimated as a circle less than 5km across, which will make the recovery operation swift and easy. After splashing down in a predetermined sea area, the recovery ship will approach to pick up the HRV. The side hatch will be used for quick access to samples returned from the ISS, some of which will be transported from the ship via airplane service to users in Japan. To ensure swift and easy access after splashing down, JAXA is researching another safe recovery sea area in the North Pacific Ocean, which will hopefully be near Japan. (The current HTVs destructive re-entry area in the South Pacific is too far and inadequate for recovery operation.) Fig.16. HRV aerodynamic shape.

[Dimensions of HRV] Diameter : 4.2m Height: 3.3m Volume: CTB115 Weight: 6.5 metric tons (includes payloads up to 1.60 metric tons)

6.2. Thermal protection HRV returns from LEO and does not need a mighty thermal protection system like the Hayabusa capsule due to its relatively low re-entry speed and thermal environment. Figure 17 shows how the requirements to the thermal protection differ for each orbital mission. However, the HRV needs a much larger surface to be thermally protected than other capsules in past JAXA missions, hence the much greater need for lightweight (low density) material than others, the development of which may be included in that of the HTV-R development. If it is developed, the lightweight material will also be used manned for re-entry vehicles.

Fig.15. Re-entry and recovery operational flow.

6. HRV Subsystems JAXA is proceeding with some investigations of the HRV hardware to mitigate the number of concealed development risks. The following sections also show examples of subsystem studies.

6.1. Aerodynamic shape The current aerodynamic shape of the HRV is shown in Fig.16. The HRV design is limited in weight to keep the total vehicle (HTV-R) within the same weight as original HTVs for Fig.17. Ablation materials and HRV requirement. launch. The 4.2 m diameter was selected as a reasonable size for the limited weight, which would also be reasonable for the structure. There are plans for new adopter to use the same 6.3. Avionics structure (4.2 m) as the HTV. Also the same diameter as the The avionics subsystem design has yet to be fixed, but HRV makes it structurally ideal. experience in HTVs avionics development represents a solid

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design basis. The HRV avionics should have sufficient From the perspective of the hardware/propellant balance, redundancies, while it is also preferable to allow for future thrusters consume little propellant during re-entry because of enhancements for the manned vehicle. Figure 18 shows a the short period for control, hence a propellant-efficient schematic of the avionics in the HRV. It includes redundancy system is not the highest priority in HRV and other re-entry in functions to manage failures occurring in itself. To enhance vehicles. However, there is a significant need for the system toward the manned vehicle level, emergency volume-efficiency in hardware. Re-entry vehicles have a components will be installed into the schematic to satisfy small width between the outer shield and pressurized structure safety requirements after any two failures occur. and have limited usable volume for the propulsion system. The power system in the HTV-R, the rechargeable lithium Figure 20 shows an example of a mono-propellant propulsion battery unit which was developed for the HTV, is used and system for the HRV, which has a simplified redundant system. will also be deployed for the HRV avionics system. The The low toxicity propellant is far better for HRV, which is battery system was authorized as human rated throughout handled both during sea recovery and operations on ship. HTV development safety review process and is one of the safest lithium batteries for space use.

Fig.20. Propulsion system schematic diagram (example). Fig.18. Avionics system (example). 6.5. ECLSS Basically the same ECLSS (Environmental Control and 6.4. Propulsion Life Support System) such as air circulation, illumination, A re-entry vehicle should have thrusters to control its etc.) as HTV is planned as shown in Fig.21. HRV has a much attitude. In particular, the importance here is greater than for smaller IVA volume than the original HTVs pressurized capsule type re-entry vehicles because of the lack of air section and can be simplified. control surfaces to adjust the angle of attack. Figure 19 shows the layout of the thrusters, which control three axes of the vehicle. To minimize the thermal input during re-entry, all thrusters are located on one side of the vehicle. HRV will conduct lifting a re-entry flight by inclining its attitude toward the opposite side of the thrusters.

Fig.21. ECLSS in HRV pressurized section.

6.6. Active cooling system HTV does not need any active radiation system and uses only passive radiation. However, the HRV surface is covered with thermal protection materials and some form of active thermal radiation system will probably be required to radiate all heat. It will be used for all avionics boxes and refrigerators Fig.19. RCS thruster layout (example). for cargo service in the HRV.

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6.7. Recovery system At the end of re-entry flight, the HRV deploys parachutes to References decrease the velocity and splash down softly. A combination of two or three main parachute and redundant pilot chute is 1) Imada, I.: Manned Spacecraft Development Plan from HTV the baseline, which are ejected by mortars, as is done by other Technical Heritage, ists27 (2009), 2009-g-02. 2) Anon, Plan to Support Operations and Utilization of the International re-entry vehicles. Space Station Beyond FY2015, NASA 2009. HRV is not expected to recover on ground in any case, 3) Sasaki, H. : HTV Development and the Future Vision, ists25 eliminating the need for contingency landing equipment. It (2006), ISTS 2006-o-1. may be a mandatory system in a manned vehicle for 4) Anon.: Apollo Operations Handbook Block II Spacecraft, SM2A-03-BK-II-(1). contingency escape at the launch pad and the need for an air 5) Anon.: NASA's Exploration Systems Architecture Study, bag system will be studied again in the manned vehicle NASA-TM-2005-214062. development in future. 6) Anon.: DragonLabTM Fast track to flight, SpaceX 7) Rex D. Hall, David J. Shayler : Soyuz – A Universal Spacecraft, Springer Praxis Publishing

7. Conclusion A detailed development plan is necessary before starting the program in order to estimate the total budget to complete. In HTV-R, there are also three further reviewing processes before commencing the development as a formal program in JAXA, within which the first launch schedule will be set. However, even now, the HTV-R target is set clearly by selecting a larger re-entry vehicle (Optoin-2) in the concept as shown in Fig.22. Once JAXA has started HTV-R development, it will be a solid step midway through the development of urrent HTV and future manned spaceships. The first HTV-R flight and HRV re-entry will represent one of the major milestones in Japanese human space activities.

Fig.22. Development flow toward a future manned spaceship

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