Rocketry - Payload vs the actual Rocket

[TimberWolfAu]

Hey all,

Got a question, watching a discussion on FB at the moment, but is there an official line between the payload of a rocket and the rocket itself (ie the delivery vehicle), or is it situational?

For example, would we consider the LM as the payload to the lunar surface, and the CSM/third stage were the delivery vehicle, but at the same time, the LM AND CSM are payload going to lunar orbit, and the third stage is the delivery vehicle? And to go even further, is the CSM, LM, third stage all considered the payload to Earth orbit, with the first and 2nd stages the delivery vehicle (and would we count part of the third stage too?)

Feels like a situation where there might be some grey area, and would come down to personal/organisational preference as to what is classed as payload vs delivery vehicle for each situation.

[onebigmonkey]

If it's the one I'm thinking of I've been a bit baffled by that discussion, and don't think the OP's terminology is helping.

He's presenting (I think) the combined mass of the CSM/LM, and isn't mentioning the SIV-B, which is what actually fired off that combination to the moon.

He's then saying the SLA panels were discarded 'just before' LOI,  when they were discarded  pretty much straight after TLI.

He's doing is usual thing of just firing numbers and equations at things regardless of whether it's appropriate!

[Peter B]

Without knowing what the discussion is about, I can't offer any (non-expert) insight.

However you might like to check out the Everyday Astronaut video about debunking Apollo hoax arguments. Near the end of the video he applies the Rocket Equation to each engine burn, working backwards from the TEI burn. For each burn he clearly explains how each value for spacecraft mass is calculated. That might provide some ideas about how to differentiate between booster and payload for each part of the mission.

[JayUtah]

The standard measure of rocket capacity is mass either to low Earth orbit (LEO) or to geostationary orbit (GSO). The uprated Saturn V used for Apollo J-type missions had a rated capacity of something like 95 tons to LEO, but obviously you can't apply that blindly because the mission profile includes relighting the S-IVB and using a substantial portion of that fuel for TLI. And yes, the proper approach is not to arbitrarily divide vehicle from payload but instead to use the classic rocket equation at each burn.

[TimberWolfAu]

He's doing is usual thing of just firing numbers and equations at things regardless of whether it's appropriate!

Makes it classic Najak.

I'm baffled by the repeated "the panels were only accelerated to 95% TLI" comments, even after he was advised that the panels were discarded after the TLI burn was done. But even the general comparisons don't feel right, Starship, Saturn, SLS, they all have different mission profiles, they don't work the same way. I mean, for starters, Starship has to return itself to the Earth, so there's a whole lot of "wasted" mass if we're only caring about going to LEO, but we haven't even seen the lunar version yet (Starship HLS).

[TimberWolfAu]

While I'm thinking about it, there was a video I found from a comment in one of the old threads (if I knew which one, I wouldn't be posting), where someone was working back through the numbers for the rocket equation for the various stages of the Apollo flights, from the moon back to launch, going over the numbers with each stages sets of mass, thrust etc

Anyone remember this video? Thought it was Astrobrant2, but apparently not.

[bknight]

Bob B had these calculations in his spreadsheet.  He helped me develop a similar spreadsheet, but there is a problem sometime after S-II fires so I canthelp you but I can remember that his sheet was very close to actual historical data.

[Dalhousie]

He's doing is usual thing of just firing numbers and equations at things regardless of whether it's appropriate!

Makes it classic Najak.

I'm baffled by the repeated "the panels were only accelerated to 95% TLI" comments, even after he was advised that the panels were discarded after the TLI burn was done. But even the general comparisons don't feel right, Starship, Saturn, SLS, they all have different mission profiles, they don't work the same way. I mean, for starters, Starship has to return itself to the Earth, so there's a whole lot of "wasted" mass if we're only caring about going to LEO, but we haven't even seen the lunar version yet (Starship HLS).

Don't forget different propellants and engine performances are also a factor.