Why would NASA even consider using belly-mounted propulsion?

[llivinglarge]

It simply isn't safe... Look at all of the debris that shed off of Discovery, ET, and SRBs.<br /><br />Why would NASA still have the Shuttle-C on the table for a shuttle replacement?

 

[tomnackid]

Because the design of the main fuel tank incorporates a thrust structure designed for side mounted engines and payload, also the current launch pad is designed with a flame diverter, noise suppression systems, hold downs, etc. for a vehicle with engines mounted on the side. Changing the design of the fuel tanks and the launch pad would increase the development cost of any shuttle derived vehicle making the whole justification of an SDL (lower development costs) moot. <br /><br />Debris really isn't a problem for a Shuttle C since it is never intended to reenter the atmosphere anyway, it won't even have a heat shield.

 

[hurricane4911]

Shuttle-C + IUS = a pretty formidable launch vehicle.<br /><br />To, it just makes sense to resuse the technology and the launch pad for a cargo carrier.

 

[radarredux]

> <i><font color="yellow">Debris really isn't a problem for a Shuttle C since it is never intended to reenter the atmosphere anyway, it won't even have a heat shield.</font>/i><br /><br />It depends on what the mission architecture looks like.<br /><br />The side-mounted solution is faster to develop, cheaper to develop, and easier to develop. But its limited mass capability (compared to inline SDHLV) will probably introduce more complicated mission architectures which can raise operational costs and risks.<br /><br />For example, the side-mounted SDHLV will probably require at least one Earth Orbit Rendezvous (EOR), which means two rockets (the SDHLV & CEV) will need to be launched in relatively short order for every mission. On the other hand, the inline SDHLV could launch the entire package, including the crew directly to the moon in a single launch.<br /><br /><b>Side-mounted approach</b><br /><ul type="square"><li>Two rocket developments<li>Two rocket launches per Lunar mission<li>At least one orbit rendezvous<br /></li></li></li></ul><br /><b>Inline approach</b><br /><ul type="square"><li>One rocket development<li>One rocket per mission<li>No orbit rendezvous<br /></li></li></li></ul><br />Note: the latter list assumes you buy ISS missions from Russia or US commercial provider.<br /><br />Note: the t/Space architecture assumed the CEV would be a reusable LEO to Lunar surface system, so only one launch (the CXV) would be needed once the Lunar CEV was in place.</i>

 

[radarredux]

Quick rough sketches:<br /><br /><b>Architecture 1: Inline SDHLV plus LEO CEV</b><br /><ul type="square"><li>Develop LEO CEV and booster (e.g., single stick SRB).<li>Develop inline SDHLV plus Lunar CEV<li>ISS mission, 1 launch of LEO CEV<li>Lunar mission, 1 launch of Lunar CEV on SDHLV<br /></li></li></li></li></ul><br /><b>Architecture 2: Inline SDHLV only</b><br /><ul type="square"><li>Develop inline SDHLV plus Lunar CEV<li>ISS mission, buy Soyuz launch or commercial launch<li>Lunar mission, 1 launch of Lunar CEV on SDHLV<br /></li></li></li></ul><br /><b>Architecture 3: Side-mounted SDHLV plus LEO CEV</b><br /><ul type="square"><li>Develop LEO CEV and booster (e.g., single stick SRB).<li>Develop side-mounted SDHLV plus Lunar CEV<li>ISS mission, 1 launch of LEO CEV<li>Lunar mission, 2 launches: (SRB + LEO CEV) and (SDHLV)<br /></li></li></li></li></ul><br /><b>Architecture 4: Side-mounted SDHLV only</b><br /><ul type="square"><li>Develop side-mounted SDHLV plus Lunar CEV<li>ISS mission, buy Soyuz launch or commercial launch<li>Lunar mission, 2 launches: (Soyuz or commercial CXV) and (SDHLV)<br /></li></li></li></ul><br /><b>Architecture 5: Side-mounted SDHLV only, version 2</b><br /><ul type="square"><li>Develop side-mounted SDHLV plus Lunar CEV that remains in orbit<li>ISS mission, buy Soyuz launch or commercial launch<li>First Lunar mission, 2 launches: (Soyuz or commercial CXV) and (SDHLV)<li>Subsequent Lunar missions, 2 launches: (Soyuz or commercial CXV) and (EELV, Falcon V, or something for Propellant)<br /></li></li></li></li></ul><br />Obviously each architecture has different initial development costs, operational costs, development risks (oops, found this is harder than we thought), operational risks (e.g., launching two rockets within a short window of time), dependency risks (hoping commercial providers step forward, or we remain happy with Russia), etc.<br /><br />My leanings of the current second (subject to change at any time <img src="/images/icons/smile.gif" />) is Architecture 4. It provides the quickest and cheapest path to Lunar landing.

 

[spacefire]

I'd like to put 4 SRBs on the SDHLV. Mars in one launch anyone? <div class="Discussion_UserSignature"> <p>http://asteroid-invasion.blogspot.com</p><p>http://www.solvengineer.com/asteroid-invasion.html </p><p> </p> </div>

 

[john_316]

Well the Mars mission needs a Nuclear Rocket Launched on one of those HLV's so it can propel the ship to Mars with a 67 day to 92 day travel time. <br /><br />Six months is too long for them to be in space to Mars and then stay and then come back... Whats the risk there?<br /><br /><img src="/images/icons/smile.gif" /><br /><br />

 

[grooble]

It's only too long if its a crap ship. If a good, comfortable ship was designed then it'd not be so bad. But the tin can stuff isn't good enough for those long journeys. <br /><br /><br /><br /><br />