Unmanned Mars landers, ballistic or lifting entry?

[gunsandrockets]

The heatshields of Viking style unmanned landers all seem to have the same semi-conical shape as opposed to the semi-spherical shape of the Apollo or Soyuz heatshields. My question is, do the unmanned landers which use heatshields for atmospheric deceleration employ a purely ballistic entry (like a Vostok capsule)? Or do those unmanned landers use a semi-ballistic lifting entry (like an Apollo capsule)?

 

[JonClarke]

If I read this page correctly, the Viking heat shield at a lift to drag ratio of 0.18.<br /><br />Jon <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>

 

[j05h]

Modern Mars landers have used roughly Apollo-type heat shields. Check out this article for more on reentry vehicles. I'm enamored of the AmARV shape these days but will always be a capsule fanboy. <br /><br />http://en.wikipedia.org/wiki/Atmospheric_reentry<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[webtaz99]

Don't forget that the atmosphere on Mars is radically different from ours. <div class="Discussion_UserSignature"> </div>

 

[rocketman5000]

thanks for the link to that article. excellent read, I took two semesters of compressible flow in college and still felt like I know very little on the subject

 

[j05h]

>thanks for the link to that article. excellent read, I took two semesters of compressible flow in college and still felt like I know very little on the subject<br /><br />The only thing I really know about reentry vehicles is that right now you can make money with capsules. Beyond that it's really handwaving in my case. AmARV and certain blunt biconics are really interesting, as are ballutes. My background somewhat precludes the finer points of reentry physics.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[gunsandrockets]

"Modern Mars landers have used roughly Apollo-type heat shields."<br /><br />I beg to differ. The Gemini/Apollo/Soyuz heatshields are spherical sections, the unmanned lander heatshields are blunted cones. Your own link says so...<br /><br />"The sphere-cone was later used for space exploration missions to other celestial bodies or for return from open space, e.g. Stardust probe. Unlike with military RVs, the advantage of the blunt body's lower TPS mass remained with space exploration entry vehicles like the Galileo Probe with a half angle of 45° or the Viking aeroshell with a half angle of 70°. Space exploration sphere-cone entry vehicles have landed on the surface or entered the atmospheres of Mars, Venus, Jupiter and Titan."<br /><br />Here are other links with images showing the conical shape of unmanned lander heat shields...<br /><br />Mars Science Laboratory<br /><br />http://marsprogram.jpl.nasa.gov/msl/mission/images/CruiseStage.jpg<br /><br />http://www.marsdaily.com/reports/Lockheed_Martin_To_Design_Mars_Science_Lab_Aeroshell.html<br /><br />Phoenix Mars Lander<br /><br />http://phoenix.lpl.arizona.edu/multimedia/images_page/images/separation.jpg<br /><br />Mars Exploration Rovers<br /><br />http://marsrovers.jpl.nasa.gov/mission/images/aeroshell1_500.jpg<br /><br />http://marsrovers.jpl.nasa.gov/mission/spacecraft.html<br /><br />Mars Pathfinder<br /><br />http://mars.jpl.nasa.gov/MPF/mpf/mpfcruise.html#APPROACH

 

[gunsandrockets]

"If I read this page correctly, the Viking heat shield at a lift to drag ratio of 0.18."<br /><br />Thanx for the link. An l/d of 0.18 would put it in the same class as the Gemini capsule, I believe. My reading of the document is that a Viking type heat shield could provide some lift for controlled entry but not enough desired for the 'smart lander' project. That leads me to think the 'heritage' probes all use the simple purely ballistic technique, not a lift generating re-entry as the manned semi-ballistic capsules do.

 

[j05h]

Sorry, guns, it's been a while since I read that page,and i've been distracted with the XPrize. Thanks for the links!<br />jOsh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>