ESA Document - Emits - ESA
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ESA Document - Emits - ESA

ESA Document - Emits - ESA ESA Document - Emits - ESA

emits.esa.int
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s Entry velocity (m/s) 12600 12400 12200 12000 11800 11600 11400 11200 11000 12515 Mission 2028 11881 Mission 2031 11501 Mission 2033 11705 Mission 2035 Earth Entry Velocity Apollo 11472 Mission 2037 11516 Mission 2039 11844 Mission 2041 12348 Mission 2043 HMM Assessment Study Report: CDF-20(A) February 2004 page 54 of 422 Figure 2-22: Entry velocity at Earth The entry velocity does not vary greatly either, it ranges from 11.4 km/s to 12.5 km/s (atmosphere rotation not taken into account). 12.5 km/s is taken as design point for the ERC so the design will fit for any mission opportunity. A summary of the mission data for the reference case is shown in Table 2-13: Phase Duration (days) Departure 08 April 2033 Earth departure window 21 Earth to Mars 207 Mars arrival 11 November 2033 Around Mars 553 Mars departure 28 April 2035 Mars departure window 21 Mars to Earth 206 Earth arrival 27 November 2035 TOTAL in space 413 TOTAL mission 963 % around Mars 58 Kick ∆V (m/s) TMI 3639 Hyperbolic Earth escape velocity 3200 MOI 2484 Hyperbolic Mars arrival velocity 3413 HEO insertion 1187 TEI 2245 Hyperbolic Mars escape velocity 2990 EOI 3598 Hyperbolic Earth arrival velocity 3052 Earth Atmosphere Entry Velocity 11505 TMI+MOI+TEI 5884 TMI+TEI 8383 TOTAL 11966 Table 2-13: Mission 2003 opportunity relevant data

s HMM Assessment Study Report: CDF-20(A) February 2004 page 55 of 422 This opportunity minimises the total mission duration as well as the time spent in deep-space (inbound and outbound trips) and maximizes the time spent around Mars. Therefore, it maximizes also the ratio time around Mars / time in deep-space. Finally, it offers one of the lowest entry velocities on return to Earth, although the approach followed for the ERC design reduces the influence of this parameter. 2.7.6.2 Surface stay duration One of the objectives of the study is to select the simplest mission case. A long stay duration on the surface would imply a much higher complexity of the mission, as more resources and infrastructure would be required to support the astronauts while on the surface, typically more complex life support systems, more consumables, more habitable volume and higher power demands in general. This increment in the mass of equipment required for a long stay would imply the definition of a cargo mission to take all the extra infrastructure. This would lead to the new requirement for the lander, of high precision landing, as the astronauts will have to rendezvous with the infrastructure on the surface. To avoid this complication, a short stay duration on the surface of Mars has been selected. After landing, one week is required by the astronauts to recover from the deconditioning, and it is assumed another week for the launch preparation. Taking into account the recommendations for the surface operations, seven EVAs are required as minimum. A surface stay of 30 days is therefore a minimum reasonable time. 2.7.6.3 Propulsion The propulsion technologies for a human mission to Mars can be reduced to the following: • Chemical propulsion o Cryogenic o Storable • Solar electric propulsion • Nuclear electric propulsion • Nuclear thermal propulsion According to the criteria defined for the mission case selection, electric propulsion has not been studied, to keep the complexity low. For the same reason and because it is not a mature technology (reduced knowledge which leads to not reliable estimations) nuclear propulsion has been also discarded. Therefore the choice remains between cryogenic and storable propulsion systems, as they are well known technologies and therefore offer a good starting point for analysis. The benefits of cryogenic propulsion is high Isp, which allows a significant reduction in the propellant mass required for a given ∆V and payload. But the drawbacks are the boil-off of the cryogenic propellants and the volume of the tanks due to the low density of the propellants. The propulsion module design chosen follows a modular approach, combining both the cryogenic and the storable system in the same mission. Three cases have been defined; all storable, all cryogenic, and cryogenic for the first manoeuvre (TMI) and storable for the remaining two (MOI and TEI).

s<br />

Entry velocity (m/s)<br />

12600<br />

12400<br />

12200<br />

12000<br />

11800<br />

11600<br />

11400<br />

11200<br />

11000<br />

12515<br />

Mission<br />

2028<br />

11881<br />

Mission<br />

2031<br />

11501<br />

Mission<br />

2033<br />

11705<br />

Mission<br />

2035<br />

Earth Entry Velocity<br />

Apollo<br />

11472<br />

Mission<br />

2037<br />

11516<br />

Mission<br />

2039<br />

11844<br />

Mission<br />

2041<br />

12348<br />

Mission<br />

2043<br />

HMM<br />

Assessment Study<br />

Report: CDF-20(A)<br />

February 2004<br />

page 54 of 422<br />

Figure 2-22: Entry velocity at Earth<br />

The entry velocity does not vary greatly either, it ranges from 11.4 km/s to 12.5 km/s<br />

(atmosphere rotation not taken into account). 12.5 km/s is taken as design point for the ERC so<br />

the design will fit for any mission opportunity.<br />

A summary of the mission data for the reference case is shown in Table 2-13:<br />

Phase Duration (days)<br />

Departure 08 April 2033<br />

Earth departure window 21<br />

Earth to Mars 207<br />

Mars arrival 11 November 2033<br />

Around Mars 553<br />

Mars departure 28 April 2035<br />

Mars departure window 21<br />

Mars to Earth 206<br />

Earth arrival 27 November 2035<br />

TOTAL in space 413<br />

TOTAL mission 963<br />

% around Mars 58<br />

Kick ∆V (m/s)<br />

TMI 3639<br />

Hyperbolic Earth escape velocity 3200<br />

MOI 2484<br />

Hyperbolic Mars arrival velocity 3413<br />

HEO insertion 1187<br />

TEI 2245<br />

Hyperbolic Mars escape velocity 2990<br />

EOI 3598<br />

Hyperbolic Earth arrival velocity 3052<br />

Earth Atmosphere Entry Velocity 11505<br />

TMI+MOI+TEI 5884<br />

TMI+TEI 8383<br />

TOTAL 11966<br />

Table 2-13: Mission 2003 opportunity relevant data

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