Why does external tank on Space shuttle fall back to earth?

[Rally]

<div class="bbWrapper">How come if the shuttle and the external tank are going the same speed and the shuttle&#039;s engines are off at external tank release does the external tank fall back to earth and not stay in orbit?</div>

 

[avbug]

<div class="bbWrapper">When the external tank is jettisoned, the orbital maneuvering system is ignited. The OMS is used to maneuver the shuttle to it&#039;s orbit altitude and track.<br /> <br /> <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms</a><br /> <br /> <blockquote data-attributes="" data-quote="" data-source="" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch"> <div class="bbCodeBlock-content"> <div class="bbCodeBlock-expandContent js-expandContent "> The <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">orbital maneuvering system</a> provides the thrust for <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_insertion" target="_blank" class="link link--external" rel="nofollow ugc noopener">orbit insertion</a>, orbit circularization, orbit transfer, rendezvous, <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_deorbit" target="_blank" class="link link--external" rel="nofollow ugc noopener">deorbit</a>, <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_ato" target="_blank" class="link link--external" rel="nofollow ugc noopener">abort to orbit</a> and <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_aoa" target="_blank" class="link link--external" rel="nofollow ugc noopener">abort once around</a> and can provide up to 1,000 pounds of <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_asm.html#srb_mod_propellant" target="_blank" class="link link--external" rel="nofollow ugc noopener">propellant</a> to the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_coord.html#aft_fuselage" target="_blank" class="link link--external" rel="nofollow ugc noopener">aft</a><a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">reaction control system</a>. The <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> is housed in two independent pods located on each side of the orbiter&#039;s <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_coord.html#aft_fuselage" target="_blank" class="link link--external" rel="nofollow ugc noopener">aft</a> fuselage. The pods also house the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_coord.html#aft_fuselage" target="_blank" class="link link--external" rel="nofollow ugc noopener">aft</a><a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> and are referred to as the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_coord.html#sts_oms_pods" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS/RCS pods</a>. Each pod contains one <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> engine and the hardware needed to pressurize, store and distribute the propellants to perform the velocity maneuvers. The two pods provide redundancy for the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a>. The vehicle velocity required for orbital adjustments is approximately 2 feet per second for each nautical mile of altitude change.<br /> <br /> The <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_1st_stage" target="_blank" class="link link--external" rel="nofollow ugc noopener">ascent</a> profile of a mission determines if one or two <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> thrusting periods are used and the interactions of the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a>. After main engine cutoff, the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> thrusters in the forward and <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_coord.html#aft_fuselage" target="_blank" class="link link--external" rel="nofollow ugc noopener">aft</a> <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> pods are used to provide attitude hold until <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/et.html#et" target="_blank" class="link link--external" rel="nofollow ugc noopener">external tank</a> separation. At <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/et.html#et" target="_blank" class="link link--external" rel="nofollow ugc noopener">ET</a> separation, the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> provides a minus (negative) Z translation maneuver of about minus 4 feet per second to maneuver the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_asm.html#sts_ov" target="_blank" class="link link--external" rel="nofollow ugc noopener">orbiter</a> away from the ET. Upon completion of the translation, the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> provides <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_asm.html#sts_ov" target="_blank" class="link link--external" rel="nofollow ugc noopener">orbiter</a> attitude hold until time to maneuver to the OMS-1 thrusting attitude. The targeting data for the OMS-1 thrusting period is selected before launch; however, the target data in the onboard <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_asm.html#gpc_mods" target="_blank" class="link link--external" rel="nofollow ugc noopener">general-purpose computer</a>s can be modified by the flight crew via the cathode ray tube keyboard, if necessary, before the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> thrusting period.<br /> <br /> During the first <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> thrusting period, both <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> engines are used to raise the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_asm.html#sts_ov" target="_blank" class="link link--external" rel="nofollow ugc noopener">orbiter</a> to a predetermined elliptical orbit. During the thrusting period, vehicle attitude is maintained by gimbaling (swiveling) the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> engines. The <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> will not normally come into operation during an <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> thrusting period. If, during an <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> thrusting period, the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> gimbal rate or gimbal limits are exceeded, <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> attitude control is required. If only one <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> engine is used during an <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> thrusting period, <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> roll control is required.<br /> During the OMS-1 thrusting period, the liquid oxygen and liquid hydrogen trapped in the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-mps.html#sts-mps" target="_blank" class="link link--external" rel="nofollow ugc noopener">main propulsion system</a> ducts are dumped. The liquid oxygen is dumped out through the space shuttle main engines&#039; combustion chambers and the liquid hydrogen is dumped through the starboard (right) side <a href="http://science.ksc.nasa.gov/shuttle/countdown/count.html#T-00H00M" target="_blank" class="link link--external" rel="nofollow ugc noopener">T-0</a> umbilical overboard fill and drain. This velocity was precomputed in conjunction with the OMS-1 thrusting period.<br /> <br /> Upon completion of the OMS-1 thrusting period, the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> is used to null any residual velocities, if required. The flight crew uses the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rhc.html#sts-rhc" target="_blank" class="link link--external" rel="nofollow ugc noopener">rotational hand controller</a> and/or <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rhc.html#sts-thc" target="_blank" class="link link--external" rel="nofollow ugc noopener">translational hand controller</a> to command the applicable <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> thrusters to null the residual velocities. The <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> then provides attitude hold until time to maneuver to the OMS-2 thrusting attitude.<br /> <br /> If the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_1st_stage" target="_blank" class="link link--external" rel="nofollow ugc noopener">ascent</a> profile for a mission uses a single <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-oms.html#sts-oms" target="_blank" class="link link--external" rel="nofollow ugc noopener">OMS</a> thrusting maneuver, it is referred to as direct insertion. In a direct-insertion <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_1st_stage" target="_blank" class="link link--external" rel="nofollow ugc noopener">ascent</a> profile, the OMS-1 thrusting period after main engine cutoff is eliminated and is replaced with a 5-feet- per-second <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> translation maneuver to facilitate the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-mps.html#sts-mps" target="_blank" class="link link--external" rel="nofollow ugc noopener">main propulsion system</a> dump. The <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-rcs.html#sts-rcs" target="_blank" class="link link--external" rel="nofollow ugc noopener">RCS</a> provides attitude hold after the translation maneuver. The OMS-2 thrusting period is then used to achieve <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_insertion" target="_blank" class="link link--external" rel="nofollow ugc noopener">orbit insertion</a>. The direct-insertion <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_1st_stage" target="_blank" class="link link--external" rel="nofollow ugc noopener">ascent</a> profile allows the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-mps.html#sts-mps" target="_blank" class="link link--external" rel="nofollow ugc noopener">MPS</a> to provide more energy to <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_insertion" target="_blank" class="link link--external" rel="nofollow ugc noopener">orbit insertion</a> and permits easier use of onboard software. </div> <div class="bbCodeBlock-expandLink js-expandLink"><a role="button" tabindex="0">Click to expand...</a></div> </div> </blockquote></div>

 

[Hugh Johnson]

<div class="bbWrapper">Gravity?</div>

 

[mzaharis]

<div class="bbWrapper">Short version:<br /> <br /> When the Space Shuttle Main Engines cut off and the tank is separated, the stack is going approximately 200 mph (if memory serves) too slow for orbit. This is quite intentional, so the tank debris will land in the Indian Ocean. As mentioned in Avbug&#039;s posts, the Orbital Maneuvering System (a couple of of 6,000lb engines) adds the additional velocity and circularize the orbit during the course of one or two two burns.<br /> <br /> Beyond that, Avbug&#039;s link is about as definitive as it gets.<br /> <br /> Schemes have been proposed to use the tanks as the basic structure for a space station. This would involve keeping the tank attached until the orbit is circularized, taking it with the orbiter.</div>

 

[bocefus]

<div class="bbWrapper">Speed at MECO is around 17,500 mph</div>

 

[Sig]

<div class="bbWrapper">So you have a space shuttle on a vertical treadmill...</div>

 

[mzaharis]

<div class="bbWrapper"><blockquote data-attributes="member: 12723" data-quote="bocefus" data-source="post: 1348642" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch"> <div class="bbCodeBlock-title"> <a href="/goto/post?id=1348642" class="bbCodeBlock-sourceJump" rel="nofollow" data-xf-click="attribution" data-content-selector="#post-1348642">bocefus said:</a> </div> <div class="bbCodeBlock-content"> <div class="bbCodeBlock-expandContent js-expandContent "> Speed at MECO is around 17,500 mph </div> <div class="bbCodeBlock-expandLink js-expandLink"><a role="button" tabindex="0">Click to expand...</a></div> </div> </blockquote> <br /> Correct (roughly). At first, I didn&#039;t understand what you were getting at, but then I realized that you may have misunderstood my post (my apologies if I phrased it in a manner that led to it being understood). I said that the shuttle 200 MPH too slow to reach orbit at MECO, not that it&#039;s going 200 mph at MECO. Basically, MECO (Main engine cutoff) is at approximately 17,400 mph (dependent on orbit). The OMS engines bring the orbiter speed up to 17,600 mph (again, depending on intended orbit).</div>

 

[minitour]

<div class="bbWrapper">I didn&#039;t think the tank actually made it back...doesn&#039;t it burn up?<br /> <br /> -mini</div>

 

[Bjammin]

<div class="bbWrapper">Yes it burns. Wonder if anyone gets to see it burn?</div>

 

[A Squared]

<div class="bbWrapper"><blockquote data-attributes="member: 14941" data-quote="Bjammin" data-source="post: 1351669" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch"> <div class="bbCodeBlock-title"> <a href="/goto/post?id=1351669" class="bbCodeBlock-sourceJump" rel="nofollow" data-xf-click="attribution" data-content-selector="#post-1351669">Bjammin said:</a> </div> <div class="bbCodeBlock-content"> <div class="bbCodeBlock-expandContent js-expandContent "> Yes it burns. Wonder if anyone gets to see it burn? </div> <div class="bbCodeBlock-expandLink js-expandLink"><a role="button" tabindex="0">Click to expand...</a></div> </div> </blockquote><br /> If an external tank burns in the outer atmosphere but there&#039;s noone there to see it burn, does it actually make a flame?</div>

 

[Bjammin]

<div class="bbWrapper">It would if it was on a treadmill! <br /> <br /> See ya at Darwins.</div>

 

[A Squared]

<div class="bbWrapper"><blockquote data-attributes="member: 14941" data-quote="Bjammin" data-source="post: 1351703" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch"> <div class="bbCodeBlock-title"> <a href="/goto/post?id=1351703" class="bbCodeBlock-sourceJump" rel="nofollow" data-xf-click="attribution" data-content-selector="#post-1351703">Bjammin said:</a> </div> <div class="bbCodeBlock-content"> <div class="bbCodeBlock-expandContent js-expandContent "> See ya at Darwins. </div> <div class="bbCodeBlock-expandLink js-expandLink"><a role="button" tabindex="0">Click to expand...</a></div> </div> </blockquote><br /> <br /> You gonna be there any time soon?</div>

 

[Bjammin]

<div class="bbWrapper">Not until July. Let you know when.</div>

 

[avbug]

<div class="bbWrapper"><blockquote data-attributes="" data-quote="" data-source="" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch"> <div class="bbCodeBlock-content"> <div class="bbCodeBlock-expandContent js-expandContent "> If an external tank burns in the outer atmosphere but there&#039;s noone there to see it burn, does it actually make a flame? </div> <div class="bbCodeBlock-expandLink js-expandLink"><a role="button" tabindex="0">Click to expand...</a></div> </div> </blockquote><br /> Yes, but it doesn&#039;t make a sound. Unlike a bear in the woods, which makes plenty of sound (especially if it&#039;s hit by a falling tree), even if there&#039;s nobody there to see it do it&#039;s thing. <br /> <br /> The real question, then, if one hand clapping will eventually burst into flame.</div>

 

[mzaharis]

<div class="bbWrapper">Sorry to be the literalist here, but, my understanding is that while the tank substantially breaks up, some debris makes it to earth.<br /> <br /> Here&#039;s chapter and verse from the Space Shuttle News Reference:<br /> <br /> After initiation of the orbiter/ET separation sequence, there is approximately 11 seconds of mated coast before the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_asm.html#sts_ov" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #0066cc">orbiter</span></a> and <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/et.html#et" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #800080">external tank</span></a> separate. The <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/et.html#et" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #800080">ET</span></a> tumble system produces a tumble rate of 10 to 50 degrees per second after separation. In <a href="http://www.ksc.nasa.gov/" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #800080">Kennedy Space Center</span></a>.launches, the <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/et.html#et" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #800080">external tank</span></a> is on a suborbital trajectory that normally results in an impact location in the Indian Ocean. Except for direct-insertion launches from <a href="http://www.ksc.nasa.gov/" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #800080">Kennedy Space Center</span></a>. the tank impacts in the Pacific Ocean. <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/et.html#et" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #800080">External tank</span></a> breakup nominally occurs during <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html#mes_entry" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #0066cc">entry</span></a> into the <a href="http://seds.lpl.arizona.edu/nineplanets/nineplanets/earth.html" target="_blank" class="link link--external" rel="nofollow ugc noopener"><span style="color: #0066cc">Earth</span></a>&#039;s atmosphere at an altitude of approximately 185,000 feet.<br /> <br /> <a href="http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html" target="_blank" class="link link--external" rel="nofollow ugc noopener">http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts_mes.html</a></div>