How high an orbit? Orion CEV launched by Ares I

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gunsandrockets

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Okay let us first assume the Ares I Crew Launch Vehicle will work as advertised and likewise the Orion manned spacecraft.<br /><br />Normal operations has the Orion spacecraft placed into LEO by the Ares I, either to rendezvous with the ISS or with a lunar-bound mission-stack. The Orion service module has enough propellant to provide 5,000 fps of delta-V (about 1.7 km/s). Normally this much propellant is reserved for the Trans-Earth-Injection burn at the later stages of a lunar mission when the Orion departs low-lunar-orbit to return to Earth.<br /><br />But what if instead a fully fueled Orion spacecraft in LEO used it's propellant to increase the size of it's orbit around the Earth? How high of a circular orbit at 28 degrees inclination could an Orion spacecraft achieve, while still retaining enough propellant for a retro burn for Earth reentry?<br /><br />The Gemini 11 mission using the docked Agena target vehicle achieved an orbit with an apogee of over 1,300 km. How high could an Orion get? 5,500 km? More?
 
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comga

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A quick review of my orbital mechanics and a few calculations says that Orion, starting in a -20 by 185 km orbit (from a recent NASA Ares-1 summary) with a total delta V of 1700 m/s (your number) and a deorbit perigee of -20 km (my guess) could go into a circular orbit of 2450 km altitude.<br /><br />Higher than Gemini 11, but not as much as you guessed. This is not the Apollo Service Module.
 
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holmec

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<blockquote><font class="small">In reply to:</font><hr /><p>This is not the Apollo Service Module.<p><hr /></p></p></blockquote><br /><br />Nice calcs <img src="/images/icons/laugh.gif" /><br /><br />But could you elaborate on what you mean by this is not the Apollo Service Module?<br /><br />ie what are the performance differenct between the two? <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>
 
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josh_simonson

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I'd note that 2450km would put Orion smack in the middle of the inner radiation belt, which is bad for spacecraft and space travelers. The radiation belt limits practical LEO missions to below 700km or so.
 
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usn_skwerl

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miles, for the win. <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> </div>
 
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comga

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in reply to:<br />But could you elaborate on what you mean by "this is not the Apollo Service Module"?<br /><br />That was a reference to the greater delta-V capability of the Apollo CM/SM, which was a tad over 2.8 km/sec vs 1.7 km/sec for Orion and its SM. 2.8 km/sec could take Orion out to 5000 km (regardless of whether anyone would really want to go there).<br /><br />Note that these are for 51.6 deg inclination orbits, because that was my starting data point. Performance is slightly better to 28 deg. The difference can be calculated.<br /><br />So a Saturn 1B could carry a vehicle capable of 2.8 km/sec and carrying five passengers. (Check out Apollo CM-119). And the advantage and advancement of Orion/Ares-1 is....<br /><br />but that is another comparison entirely.<br />
 
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gunsandrockets

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<A quick review of my orbital mechanics and a few calculations says that Orion, starting in a -20 by 185 km orbit (from a recent NASA Ares-1 summary) with a total delta V of 1700 m/s (your number) and a deorbit perigee of -20 km (my guess) could go into a circular orbit of 2450 km altitude.><br /><br />Thanx! <br />
 
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