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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/4SCYSO6F2ERZUPJY6HZ4GTVTZUL24GMT/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "4SCYSO6F2ERZUPJY6HZ4GTVTZUL24GMT",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/4SCYSO6F2ERZUPJY6HZ4GTVTZUL24GMT/?format=api",
    "sender": {
        "address": "ka3hdo (a) comcast.net",
        "mailman_id": "fa8edbc3567d4116ab189c93e04bdde1",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/fa8edbc3567d4116ab189c93e04bdde1/emails/?format=api"
    },
    "sender_name": "Frank H. Bauer",
    "subject": "[amsat-bb]  (no subject)",
    "date": "2008-02-15T10:13:32Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Joe,\n\nYou had two questions in your query and I believe that one of them (the\nheating one) was been answered.  Let me answer the second one:\n\n>So in actuality it comes down from space even slower than going up. \n>Yes?  45 min vs 10.\n\nThe reason it seems to take longer---45 minutes----to come down (as compared\nto 10 minutes to reach orbit altitude), has to do with simple orbital\ndynamics.  Or de-orbit dynamics in this case.  As you know, the Shuttle (or\nany other vehicle that is purposely deborbited) performs a deorbit burn\nabout half an orbit before landing.  This burn actually changes the orbit\nperigee (lowest point in the orbit) to be well in the Earth's atmosphere.\nOr at or below ground altitude if enough propellant is available.  \n\nRemember that the Shuttle orbit period is on the order of 90-100 minutes.\nSo about 45 minutes after the deorbit burn the vehicle reaches perigee,\nenters an appreciable part of the atmosphere, and either burns up (many\nsmall satellites), or has sufficient thermal protection to land on the\nground (Shuttle and large, dense pieces of satellites).\n\nMy team used this technique to successfully deorbit the Compton Gamma Ray\nObservatory, resulting in a safe splashdown in the Pacific Ocean.  We also\nused this technique in no atmosphere to purposefully crash the Lunar\nProspector into the moon at the end of its mission.\n\nOnce a vehicle starts to hit atmosphere (the mission control guys call this\n\"entry interface\") the heating and events to landing occur rather\nquickly..several minutes.  Because as you start to touch the atmosphere, you\ncontinue to get deeper into the atmosphere because you are dipping further\ndown to perigee altitude where the drag is much higher than at the entry\ninterface.   \n\nI hope this helps.\n\n73,  Frank Bauer, KA3HDO\n   \n\n------------------------------\n\nMessage: 8\nDate: Thu, 14 Feb 2008 20:18:15 -0600\nFrom: Joe <[email protected]>\nSubject: [amsat-bb] Re: Since We Are Off Topic Somewhat....\nTo: \"Ransom, Kenneth G. (JSC-OC)[BAR]\" <[email protected]>\nCc: AMSAT-BB <[email protected]>\nMessage-ID: <[email protected]>\nContent-Type: text/plain; charset=us-ascii; format=flowed\n\nDoes anyone have the actual speeds at each altitude going up vs coming down?\n\nI tried to find such a graph, chart, table etc, to no avail,\n\nJoe\n\nRansom, Kenneth G. (JSC-OC)[BAR] wrote:\n\n>The amount of time spent in the atmosphere at high velocity (I'd have to do\nsome digging to give some real time data but basically it is as follows).\n> \n>One the way up, the rocket goes through the 100 km of air during the slower\npart of the change of velocity and spends very little time in the atmosphere\nat the higher velocity.\n> \n>On the way down, the object starts to encounter the atmosphere at maximum\nvelocity and therefore maximum friction. It will be in the atmosphere for\nthe a much longer period since it comes in a very shallow angle. The object\nwill have that friction nearly the entire trip to the ground even though the\ndrag from the atmosphere will slow the object. \n> \n>Kenneth - N5VHO\n>\n>________________________________\n>\n>From: [email protected] on behalf of Joe\n>Sent: Thu 2/14/2008 5:55 PM\n>To: 'AMSAT-BB'\n>Subject: [amsat-bb] Since We Are Off Topic Somewhat....\n>\n>\n>\n>Hi All,,\n>\n>Since we are somewhat off topic for the moment with the conversation\n>about the bird to come down shortly..\n>Ok,  the question is,  and I've asked it to several other places, and\n>yet to even get a answer,\n>\n>The question is,,,\n>\n>Space shuttle launches,,  starts off at sea level,  and in less than ten\n>minutes goes from  zero to 17K MPh (or so)  And gets to orbital altitude.\n>\n>Time to come down,, the de-orbit burn happens to slow it down just a bit\n>to cause the orbit to more or less decay.. It's at orbital altitude..\n>and moving at about 17K MPh..  45 minutes or so later it's back on the\n>ground and moving at zero MPh..\n>\n>So in actuality it comes down from space even slower than going up. \n>Yes?  45 min vs 10.\n>\n>Ok,  same goes with any satellite,,\n>\n>How come,  going up,,  0 to 17K MPh through the atmosphere, all  is\n>fine..  BUT\n>\n>coming down,,  17K MPh  to 0  unless it has protection  it will  burn up\n>in the atmosphere from friction with the air.\n>\n>why is it different?\n>\n>Joe WB9SBD & NSS\n",
    "attachments": []
}