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The required technologies and the related need for demonstration in Europe, USA and Japan

As an introduction to the activities that would be performed in the frame of IRENA project, the next sections present possible fields of interest for re-entry technologies. Other fields of interest will be identified and investigated in the frame of IRENA project.

• Aerocapture:

Aerocapture is an aero-assisted technology for Solar System exploration that uses a single pass through a planetary atmosphere to decelerate a spacecraft coming from a hyperbolic interplanetary trajectory and achieve a targeted elliptical orbit. Such a manoeuvre is really attractive with respect to mass saving compared to more conventional techniques of insertion using propelled braking. This technique enables to place large robotic loads into Mars orbit, could facilitate access to Phobos and Deimos and support human exploration on Mars. Critical issues are linked to, guidance, innovative high Lift-Drag concept, GNC algorithms for both pre-aerocapture and aerocapture phases and thermal protection systems.

Figure 1-4: Aerocapture principle (credit: Astrium) – the aerocapture manoeuvre requires of very sophisticated control technology including autonomous control.

• Sample return missions:

The sample return missions from asteroid or from Phobos are precursor missions which pave the way to Mars Sample Return (MSR) which is a priority for the planetary science community (ISECG report).

In the frame of ESA MarcoPolo-R and Phootprint missions, the Earth Re-entry Capsule (ERC), that has to safely deliver the sample container on Earth was designed as fully passive (no parachute). The impact on ground is absorbed by a crushable material that protects the samples from severe decelerations that could damage them. Other critical issues for sample return re-entry are the capsule stability, the aerothermal environment during entry (very high entry velocities) and the capability of the beacon to withstand the impact on ground.

            

Figure 1-5: Rastasspear and MarcoPolo-R Earth Re-entry capsule (Astrium design) – No parachute – Crushable material protects the samples from severe deceleration at impact.(credit: Astrium)

• Mars Precision Landing:

Future exploration missions to Mars, including the Mars Sample Return (MSR) mission, will require an accurate landing of the vehicle in close proximity to surface features and sampling sites of high scientific interest. A high precision landing capability will ensure the investigation of high quality samples by the lander. Guidance Navigation and Control as well as Entry Descent Landing technologies were identified as key enabling technologies to achieve precision landing on Mars in the Robotic Exploration Technology Plan. Recent on-going activities on Mars Entry, Descent and Landing aim to demonstrate the feasibility of achieving a 10km landing accuracy. Significant additional efforts are however required on each of the EDL phases, as well as on the end-to-end optimisation of these phases to further improve the final landing accuracy below 10 km towards a high precision level (below 3 km) and possibly to pinpoint landing (i.e. 100m).

In order to achieve pinpoint landing, one has to perform a simultaneous optimization of worst case trajectories and landing precision and vehicle design (coupling covariance analysis tool and optimizer). Main issues are linked to global optimization of guidance algorithms on re-entry, descent and landing phases (supersmart parachute, minimization of propellant consumption during landing) and camera based absolute navigation algorithm robust to guidance and hazard avoidance schemes. Mandatory technologies improvement are needed on large parachute deployment domain, sky crane and propellant architecture as well as sensors suite (accelerometer and gyrometers calibration, image processing, miniaturised Lidar or Doppler-radar).

Figure 1-6: MPL EDL sequence (credit: Astrium)

• High Mass Landing

NASA’s system studies have shown that large entry decelerators provide a potentially enabling means to increase landed mass on the Martian surface, as well as the consideration of a whole new class of missions. Inflatable Aerodynamic Decelerators (IADs) are an identified solution for hypersonic entry, allowing to lower the ballistic coefficient by increasing the surface with low mass impact. This is an alternative to the conventional rigid and heavy thermal protection of the vehicle heatshield.

Figure 1-7: IRDT (inflatable re-entry demonstrator Technology) artist view – credit: ESA

The primary application of such concepts may be at Mars due to its tenuous atmosphere, but other applications, including ISS downmass and the landing of large payloads on other atmosphere bearing bodies, are possible. Various concepts exist such as flare, hypercone, trailing sphere or torus and each of them presents the advantage to aerodynamically stabilize the inner vehicle, and active control is therefore not necessary.

The re-entry technologies associated to the different fields of interest are listed in the table below. Each identified re-entry technology could be demonstrated either by a ground demonstrator or by a flight demonstrator. If possible advantage will be taken from the ISS facility.

 

(*)Flight demonstrators could be designed as:

• Passenger of a science mission (LEO, Moon, Asteroid, Mars),

• Passenger of a cargo mission to ISS (e.g. HTV),

• Dedicated mission,

• SRM (Sounding Rocket Mission).

It has to be noted that ISS offers a unique, essentially low cost, rapid access to space and using station as a platform to launch demonstration experiments provides combined EDL conditions relevant for technology development and demonstration.

(**) Ground facilities enables demonstrate technologies at subsystem level in a relevant environment. Some examples of ground demonstrations are listed below (the list is not exhaustive):

• Balloon or helicopter drop tests,

• Crash tests facility at NASA Langley Research Center (see Figure 1-8),

• GNC tests on Astrium’s HOMER (Hover ManEuveRs) platform (see Figure 1-9),

• Arc jet testing,

• Free flight tests in a ballistic range…

                                                                                                                                 

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