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Comment by antimagic | Hacker News Reader

This needs a [2011] in the title, which is important as the space industry has changed a lot in the last few years, particularly with the arrival of SpaceX and other COTS competitors. Whilst it's true that no-one is planning a beast like the Saturn V (although the Falcon 9 Heavy is getting close), it's also true that these days we don't need that.

Back in the 60s/70s, it was not possible to do an automatic hook-up of modules in space. Today we do these routinely. Those Apollo missions could still be launched today by launching the command module, the service module and the lunar module as separate payloads and joining them in orbit. The crew would launch in the command module.

It's a bit like regretting that Formula 1 cars no longer have big 3.0L V12 engines, and instead have to get by with measly 2.4L V8s, whilst missing the fact that the modern car will eat the V12's lunch, with it's eyes close, in reverse.

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Not exactly. The "real" difference is if we cut down to a 4 cylinder at half the horse power, half the torque. While a "newer" engine does achieve higher thrust to weight nobody is building engines with anywhere close to the trust of the J-2.

NASA actually is attempting to rebuild the J-2, with the J-2X program. The problem is nobody knows how the J-2 works and part of the contract included NASA shipping several J-2's back for re-engineering.

I should also remind you that a year ago NASA didn't actually know "how" the j-2 worked. Their numbers said the bell should melt during flight. Eventually they realized that helium is injected on a outer ring of injectors to insulate the bell.

My point was more that you don't need the raw thrust of the F-1 / J-2 so much these days because we've made up for the lack of single-launch capacity by advances in other areas. Look at the ISS - it could not have been launched with Apollo-era tech, because the Saturn V couldn't launch it in one hit, and they didn't know how to put things together on-orbit. +(see edit)

These days it becomes a cost/benefit analysis - is the extra cost of doing things in one big monolithic lift more or less than the extra cost incurred by having to break things into smaller components and assemble on orbit. Clearly heavy lift still has advantages - there's a reason everyone is excited about Falcon 9 Heavy, but rockets are tricky beasts, and multiple smaller launches helps mitigate against catastrophic failure (although it may increase the risk of partial failure).

Edit: Just to be clear, I'm talking about automatic on-orbit assembly, which means that you don't have to launch a pilot + life support each time you want to join two bits together.

Actually it is far better to minimize the number of launches to complete any mission. For example, Elon Musk has repeatedly mentioned that he is not currently a fan of in-orbit assembly. So having a really powerful engine is of great utility. The problem is one of cost-benefit. Having a huge engine means a big rocket which needs to be launched multiple times to achieve economy. But there are not too many missions around which require such capacity. Just look at the proposed SLS cadence. So having a Falcon Heavy with 27 engines is a much better solution any way. I cant wait when Merlin 1Ds are replaced with Raptors on first stage on Falcon Heavy. That would be one monster of a rocket.

> Actually it is far better to minimize the number of launches to complete any mission.

Doubtful. To design a big rocket takes a lot of money - and big rocket doesn't get to be used as much as a smaller rocket sometimes, which makes it more expensive per flight.

The opinions of Elon Musk aren't always perfect either. Certain technical decisions are made not because they are best, but because they are available - like, SpaceX just knows how to do that, and considers it expensive to learn the alternatives. Which is quite justifiable on economical grounds.

Your argument is that orbital assembly didn't exist in the Apollo era, when Orbital Assembly WAS the runner up to the SaturnV single launch option [Source Original Posters Article].

This means logically some times its more cost efficient, or simpler to put 27 tons in orbit in one launch, then assembly 6 5 ton launches.

> I should also remind you that a year ago NASA didn't actually know "how" the j-2 worked. Their numbers said the bell should melt during flight. Eventually they realized that helium is injected on a outer ring of injectors to insulate the bell.

I think this is remarkable, given that film cooling of the nozzle is a known aspect [0] of the first stage engines of Saturn V.

[0] Thrust Chamber Nozzle Extension section on page 3 http://history.msfc.nasa.gov/saturn_apollo/documents/F-1_Eng...

That's wrong. Vulcain 2 on Ariane 5 flew four times in 2013. It's a 1340 kN thrust LOX-hydrogen engine. By contrast the J-2X will have 1307 kN.

Also the F-1 engine has been surpassed in thrust and efficiency by the Russian RD-170 family which flies today in the Zenit rocket.

I'm sure you could learn a lot from studying the J-2 and J-2S. No harm in that. But mystifying Apollo has done a lot of harm to sane space technology engineering and policy.

Sources: http://www.arianespace.com/news-launch-logs/2013-2014.asp http://www.sea-launch.com/missions-q1-past_launches.aspx http://www.spacelaunchreport.com/log2013.html

They (well, contractors) are re-engineering the F-1B as well: http://arstechnica.com/science/2013/04/new-f-1b-rocket-engin...

> Back in the 60s/70s, it was not possible to do an automatic hook-up of modules in space.

Well, maybe not for Americans. The first Soviet space docking (October 30, 1967, a year and a half after the first US space docking, with Gemini 8 on March 16, 1966) was between the unmanned Kosmos 186 and Kosmos 188 and was automated.

Soviet moon missions using multiple launches and automated docking were considered, at least briefly: http://www.astronautix.com/articles/theoblem.htm

Actually, NASA is planning a Saturn V-sized launch vehicle, under the name "SLS" ("Space Launch System"). SLS Block II is supposed to match the Saturn V's capacity, but it won't launch until the 2020s.

(There are also rumors of very large rockets in advanced planning at SpaceX, but the only possible component of that program that has yet been announced is a methane-fueled staged combustion rocket engine, "Raptor" --- and they only announced that when they started reserving time for component tests at NASA facilities. So, even if those rumors are true, it's likely to be a while before they're confirmed in any detail.)

F1 Just changed to 1.6 V6 With a Twin Turbo and a massive energy recovery system, and people are doing nothing but complaining.

Then why is Spacex looking at building an engine the size of an F1, or larger?

Agreed. Separate launch was actually one of the scenarios considered by NASA. The had F1 engine ready for Saturn so it was not necessary.

But three ships (live module, landing module and return booster) with randevu at moon orbit is the most fuel efficient scenario.

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