Thrust From United States of America, joined Sep 2003, 2691 posts, RR: 9 Posted (3 years 11 months 1 week 6 days 1 hour ago) and read 7916 times:
Hi there. I was wondering which space vehicle had an overall better performance launchwise? The Saturn V could lift more payload, but it took longer to reach orbital velocity than the shuttle. It also used more engines to get into orbit, but the result was that it was able to go a greater distance before main engine cutoff. I'm not sure if that's an advantage or not. The first stage booster burned for just over half a minute longer than the solid rocket boosters, but was capable of getting its payload up to a MUCH higher velocity than the SRBs, and by 2 minutes, both the Saturn V and the shuttle were going approximately the same speeds. It also seems like the shuttle didn't have nearly as great a fuel capacity as the Saturn V either, but it seems that... I don't know for certain. In any case, if somebody more knowledgeable in this area than me can comment, I would appreciate it. I also will not be nearly as chatty this time. Thanks.
kalvado From United States of America, joined Feb 2006, 540 posts, RR: 0
Reply 2, posted (3 years 11 months 1 week 6 days ago) and read 7896 times:
Parameters you quote are not too relevant to "performance"
You may quantify performance in terms of $/kg of on-orbit mass, or as %% of takeoff mass delivered to the orbit.
Most launch vehicles would be in a $6-10 /gram range on first number (just to compare - gold is $48/gram as of last Friday. 10 years ago gold was in $10/gram range). Mass-wise, most mid-size launch vehicles are around 3% of mass to orbit; Japanese H-2 being leader at 4.2%; Saturn V is around 4.0%, if my memory serves me right. It's hard to define comparable value for shuttle, since one can argue what should be counted as payload in that case.
Moreover, launch site and destination orbit can change everything. New external tank had to be developed for Shuttle to fly to 51.6 deg. ISS/ Mir orbit. As far as I know, Shuttle would be unable to reach orbit if launched from Russian launch site Bajkonur with empty payload bay.
Next, initial acceleration - is a result of many trade-offs. It can be different even for different rockets in a same family. I remember Boeing's document describing capabilities of Delta rocket with acceleration charts. pretty much every configuration has different acceleration profile.
Basically you do not want to accelerate too much in dense atmosphere, but you don't want to stay there too long. In both cases you loose much needed velocity. Oh, and you want to limit aerodynamic loads and peak acceleration as well, and engines have their limits as well..
Difference between S-5 and Shuttle is in first stage engines - and approach to go through the air. Shuttle use higher thrust, lower specific thrust boosters to kick it out of lower atmosphere, where lower-thrust, higher specific thrust H2 engine can take over.
S5 uses same fuel - H2 - to steadily power it's way through.
Sinlock From United States of America, joined Dec 2000, 1664 posts, RR: 2
Reply 3, posted (3 years 11 months 1 week 5 days 7 hours ago) and read 7704 times:
Quoting kalvado (Reply 2): Saturn V is around 4.0%, if my memory serves me right. It's hard to define comparable value for shuttle, since one can argue what should be counted as payload in that case
That can also be said for S-V. Figuring that a fair amount of the propellent in the 3rd stage could be concidered functional payload. Being that most is used to cut down lunar transit time due to the limited space for consumables such as Oxygen, water, and food.
rwessel From United States of America, joined Jan 2007, 2579 posts, RR: 2
Reply 4, posted (3 years 11 months 1 week 5 days 2 hours ago) and read 7625 times:
Quoting Sinlock (Reply 3): That can also be said for S-V. Figuring that a fair amount of the propellent in the 3rd stage could be concidered functional payload. Being that most is used to cut down lunar transit time due to the limited space for consumables such as Oxygen, water, and food.
Or it could be used to boost a payload into a higher orbit. So the same could be said of any booster that's bigger than is nominally needed to put its payload into LEO. The S-IVB's (semi) unique ability to be restarted makes it usably as an alternative to a dedicated transstange for that sort of mission. Or you could burn out the S-IVB on the way to LEO, allowing more payload. Or the S-IVB simply be deleted from the stack if not needed (ala Saturn INT-21, aka Skylab).