When designing an expendable launch vehicle...

[pmn1]

When designing an expendable launch vehicle, what needs to be looked at?<br /><br />Choice of solids or liquid fuel<br /><br />Size of core<br /><br />Number of boosters (again solid or liquid)<br /><br />Size of boosters – different to the core (as in Ariane) or same as the core as in Delta IV<br /><br />Vertical or horizontal assembly.<br /><br />What other things have to be considered? <div class="Discussion_UserSignature"> </div>

 

[h2ouniverse]

Few additional items, non exhaustive:<br /><br />Number of stages<br /><br />Structural tanks (Ariane) versus external structure (Russian)<br /><br />Flight Control electronics<br /><br />Injection strategy (LEO, GTO, direct GEO injection)<br /><br />Network of ground stations<br /><br />Launch site, close to equator, on an Eastern coast, with stable weather<br /><br />Industrial organization<br /><br />Ability to transport the modules from production to integration and launch site<br /><br />Fairing ejection design<br /><br />Capabilty to launch multiple satellites<br /><br />Pogo effects<br /><br />Use of non toxic materials for re-entering stages<br /><br />Sizing burnt stages re-entry in safe places<br /><br />...

 

[jimfromnsf]

First thing to determine is the size and weight of the payloads and what orbit is it going to.

 

[vulture2]

Cost and price, particularly recurrent operational costs, including logistics, infrastructure, and man-hours.<br /><br />A government contract, usually essential for a new startup.<br /> <br />And try not to use any solid fuel. In the long run, it's expensive.

 

[radarredux]

> <i><font color="yellow">When designing an expendable launch vehicle, what needs to be looked at?</font>/i><br /><br />At the time you expect to be operational, who you expect the customers will be (what do they want to launch, to where, and how much they are willing to pay for it) and who the competitors will be (what markets are they targeting and what their cost structures will be).<br /><br />You should also look at the history of launch vehicles, understand what did and didn't work (both technically and commercially) and why.<br /><br />Then you need to look at what the expected devopment costs will be, and once you become operational, what your fixed costs will be (e.g., maintaining a launch crew and facilities) and your variable costs will be (e.g., the costs of the materials to build the rocket). Then, if you are in this for the money (i.e., you want to run a business or attract other people's money), you need to look at your expected launch rates, what you expect to be able to charge the customer, include development, fixed, and variables costs, and identify a point in which the investments turns positive. Actually, since potential investors have alternative places to invest their money, you need to consider when you meet some target profit assuming the development costs where invested at 10% compounded interests.<br /><br />If you put all this in a spreadsheet, then you can play with the numbers to see what makes since. For example, "Assuming a development cost of X, a fixed cost of Y, a variable cost of Y..., I can create a positive return on investment in K years". This gives you a foundation on how to pursue the technical details. For example, if you choose to invest heavily into development (e.g., to use a methane engine), how much will operational costs (fixed and variable) need to be held down in order to justify that development cost?</i>

 

[gunsandrockets]

You want to use high-thrust lower-ISP boosters and lower-thrust high-ISP upper stages. Ideally an expendable would only use two stages to reach LEO, and three stages for beyond LEO. The Saturn V is a classic example.<br /><br />The common core booster design seems very popular. It's used by the EELV and the Falcon 9. The Chinese and Russians are now moving in that direction with the CZ-5 and Angara rocket projects. <br /><br />Another common design feature is four liquid strap-on boosters, making a nice symetric arrangement. The Russians, Chinese and Japanese do this.<br /><br />I think there is a practical upper-size limit to space launchers. Anything larger than the CZ-5 is probably more trouble than it is worth. Transportation of components to the launch site and launch site handling of very large boosters is a huge headache. The failure of the Soviet N-1 rocket is partially attributable to those problems.<br /><br />To achieve difficult manned-spaceflight objectives things like orbital refuelling, dry launch, high ISP space propulsion, and Earth-Orbital-Rendezvous of elements launched by medium lift rockets should be used instead of using giant Saturn-class Heavy Lift Vehicles. <br /><br />