It needs of the translate ability because of the sample colector. The spacecraft is going to make a station keeping to Phobos, and the long instrument, the sample colector, will touch in the Surface of Phobos, grab a rock, and make some studies of the sample... Maybe in the future, a manned spacecraft could be sended to bring the spacecraft and the samples back to Earth...
---------- Post added at 02:40 PM ---------- Previous post was at 12:13 PM ----------
Another pictures of the Carrier. Now the rocket engines were added. As they're not too much powerful, there are several engines. It can add stability.
---------- Post added at 02:41 PM ---------- Previous post was at 02:40 PM ----------
And another note: The engines are going to be used only in the start of the ascent and in the orbit insertion. During almost all the time the scram jets are going to be used. And the auxiliary boosters are going to be used during missions in high altitudes.