How does 1 vs. 2 engines affect Centaur?

[willpittenger]

When a Centaur has two engines, does it carry more propellant or oxidizer? If not, how would the extra engine affect flight? <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[vogon13]

Minor effects:<br /><br />The math for the trajectory is simpler to calculate as the impulse is delivered over a shorter time and the craft more closely approximates a ballistic trajectory.<br /><br /><br />Burning more of the fuel deeper in the gravitational well (for escape paths) is more efficient. You are not burning fuel to raise fuel across a gravitational gradient, you are burning fuel to accelerate the payload.<br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[jimfromnsf]

Same amount of propellant. The single engine is used for higher energy missions (GTO and earth escape) where the additional engine mass actually reduces payload mass. The same impulse is provide by the single engine as 2 engines (ie 2x thrust x 1/2 duration is equal to 1 x thrust x 1 duration for a given propellant quantity)<br /><br />Two engines are used to put heavy payload into LEO. More thrust is needed to reduce gravity losses

 

[propforce]

<font color="yellow">Two engines are used to put heavy payload into LEO. More thrust is needed to reduce gravity losses </font><br /><br />There you have it in essence.<br /><br />Engine efficiency is the same, e.g., Isp = thrust divided by propellant flow rate. Since Isp is the same, 2 engines just mean they consume 2X propellant flow rate.<br /><br />Heavy payload to LEO can afford to use 2 engines because it's still burn less TOTAL propellant than GTO missions, so the tank can accommodate 2 engine burn.<br /> <div class="Discussion_UserSignature"> </div>