MSL development & assembly, Until it's shipped to the Cape Options

[climber]

In case you missed it there's 9 minutes on MSL (actual hardware visible) + 5 minutes with Dr Elachi on "This week in Space" there: http://www.spaceflightnow.com/
14 minutes out of 23 regarding Unmanned, not bad.

[nprev]

I think I know the answer to this question before asking, but gonna ask it anyhow because it's cool: Is that attitude maneuver by the upper booster stage right after the injection burn intended to give MSL the proper angle of attack for Mars atmospheric entry? (I'm just amazed that they do it 8.5 months in advance!)

[mchan]

I think I know the answer to this question before asking, but gonna ask it anyhow because it's cool: Is that attitude maneuver by the upper booster stage right after the injection burn intended to give MSL the proper angle of attack for Mars atmospheric entry? (I'm just amazed that they do it 8.5 months in advance!)

Since the cruise stage has a propulsion system for trajectory correction, it must have some mechanism to adjust attitude for the burns. The cruise stage is spin-stabilized, and I don't recall or see how control gyros are used. So I'm guessing thrusters for attitude control. And if it has thrusters, then there is no need to orient for atmospheric entry 8.5 months early.

My guess is the orientation is to face the solar array on the back of the stage perpendicular to the Sun to maximize solar cell efficiency. Another consideration is to maximize antenna for Earth communications. The antennas are probably low-gain, omnidirectional, but even so, some directions work better than others.

[djellison]

Since the cruise stage has a propulsion system for trajectory correction, it must have some mechanism to adjust attitude for the burns.

Actually - the way TCM's are done with an MPF/MER/MSL spinner cruise stage is to not turn. You fire all four thrusters in one cluster in a pulse at some point during the rotation to adjust in that plane ( many tens of times. it's shown once in the animation) or, fire the after or fwd facing of each cluster constantly to adjust in the other 'axis'.

I wondered how on earth they did TCM's on spinning spacecraft until I met a guy from the Nav team who explained the whole process. It's very clever ( but very hard to explain with words )

At the end of cruise - they chuck the cruise stage - then use the thrusters on the descent stage ( that stick out the back of the backshell ) to despin from the 2rpm cruise spin rate and turn to entry attitude.