<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Hi Jon, I have heard this too: (that the thin atmosphere is much worse than having either a thick atmosphere as on earth or none as on the moon)linkOn the other hand, didnt the pheonix make some sort of powered landing? Does it open the way to landing much heavier payloads? <br />Posted by kelvinzero</DIV></p><p>Hi Kevin</p><p>Landing large payloadsis very challenging. But it is possible. Reading through the lines you can see how it could be done. A high lift spacecraft during entry slows down using simple aerobraking. This could either be a biconic or a lifting body. At Mach 3 you use parachutes to slow down to subsonic. Once you have slowed dwon to the parachute's terminal velocity you use rocket thrust and landing legs. As you said, no different to Phoenix in principle (except for the high lift design).</p><p>This has been known for 40 years as a feasible approach. It was disingenuous of that Universe Today article to suggest otherwise.</p><p>A study is only as useful as its assumptions. Manning's papers on the subject (Braun and Manning 2005, Wooster et al. 2007) have several unrealistic assumptions. </p><ul><li>They assume very large masses (over 100 tonnes in some cases!). No Mars mission study in the last 50 years has ever had landing masses this large (and I have at least nodding familiarity with all of them, I think). The real numbers are more like 25-70 tonnes</li><li>They assume low L/D (0.3) entry designs carrying out near ballistic flight paths, and ignore the potential for higher L/D (0.5-1.0) shapes (biconics, ellipsleds, even lifting bodies).</li><li>they assume that parachutes will not be used above Mach 2 when the limit on Mars is Mach 3 with current technology</li></ul><p>Under these circumstances it is not suprising that they conclude it is impossible with present technology. But this is misleading. The media of course loved it and ran with the "landing people on Mars is impossible" angle for all it is worth.</p><p>Larson and Pranke (chapter 10) show that a moderate lift aeroshell (L/D 0.4-0.5) can de-accelerate a 62 tonne lander from a velocity of 3.65 km/2 down to parachuite opening velocities at an altitude of 11.5 km. A single parachute with a diamter of 53.3 m with slow the lander down to 200 m/s by the time an altitud of 8.5 km is reached. At this point the engines are fired and with 719 m/s of dV bring the spacecraft to a soft landing.</p><p>Jon</p> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em> Arthur Clarke</p> </div>