Is Earth Orbit Rendezvous Still Too Expensive for Moon Missions?

[hamster143]

Someone locked the original topic for no obvious reason, but I have to comment on this:

Earth orbit rendezvous is one of the most expensive ways to go and requires an enormous number of launches. NASA rejected this option fairly early on in the Apollo program. Mass reduction was one of the key drivers in the selection of the lunar orbit rendezvous approach that was used in the Apollo program.

Fortunately, today is 2010 and not 1960, and if there's one thing that we learned in all this time, it's how to make lots of launches relatively cheaply and safely. We could've launched about 2000 tons into low Earth orbit (the equivalent of 6 International Space Stations) using Protons, and possibly three times as much if SpaceX comes through with their promises, with money that was originally allocated in NASA budget just to develop the new Ares V megalauncher.

Even though LEO launches are still incredibly expensive compared to the cost of fuel, launch costs are just a tiny portion of any sensible Moon/Mars budget. Most of the costs, I believe, are salaries of engineers who design and test new technologies and new spacecraft .

 

[mgb_phys]

The previous thread was locked because of the OP's belief that any physics he didn't understand didn't apply.

Assuming everything you are sending to the moon has to be lifted from the Earth's surface at some point then putting each piece into LEO and assembling them there before heading moonwards has no overall energy advantage.
There will in fact be an energy disadvantage because each payload needs to be put into a particular orbit and then extracted from that orbit, you also need to lift all the assembly tools and extra crew to perform it.
Generally launching large loads is more cost effective, apart from fixed per-launch costs the mass of waste launched, in terms of shrouds, 2nd stages etc scales down with payload size.

The only reason a LEO rendevous would be necessary would be if you couldn't put the entire craft into orbit in one go, such as a much larger vehicle needed for a mission to mars. The USSR moon mission was planned a series of launches were the return vessel (and a spare) would have been sent to the moon in advance - but this still didn't need an LEO rendevous

 

[hamster143]

Cost effective in terms of energy savings, does not necessarily mean cost effective in terms of $$$. A low-volume, ultra heavy lift vehicle such as Ares V might be more energy-effective in launching a complete package at once, but it might cost more per incremental launch than five or ten Proton/Falcon launches, if Protons/Falcons are mass-produced and launched 20-40 times a year, and Ares V flies once every couple of years; even if you account for extra costs of a layover in LEO.

And, if we want to get beyond proof of concept in human exploration, sooner or later we'll find that even Ares V with its 60 tons to LTI is insufficient, and that gets us back to square 1: either learning to assemble in orbit, or spending $100 billion to design an ultra-ultra-heavy-lift launch vehicle that weighs 20,000 tons (including 16,000 tons of unstable rocket fuel) and threatens to take out everything within a 20 km radius in the event of a catastrophic failure on the launch pad.

In my opinion, chemical rockets won't be used extensively to explore beyond LEO. We will assemble stations in orbit from little pieces, use ion thrusters with solar panels to explore the Moon and Mars (and possibly the asteroids), and use ion thrusters with nuclear reactors to go further than that.

 

[D H]

Fortunately, today is 2010 and not 1960, and if there's one thing that we learned in all this time, it's how to make lots of launches relatively cheaply and safely. ...

First, you are comparing apples to oranges. You are comparing the development cost of a new rocket (Ares V) to the marginal costs of an operating an existing rocket (Proton).

Regarding safety: I beg to differ. You mentioned the Proton and SpaceX. The Proton has made 294 successful launches out of 335 attempts, or an 87.8% success rate. That's not "safely." How many people would fly from New York to London if 12.2% of those flights ended with an in-flight explosion or a landing in the Atlantic? How many people would drive from their house to the bank if the chance of a fatality on such a trip was 12.2%? I don't want to get into an argument over whether driving to the airport is safer than flying. Suffice it to say that airplanes and automobiles are safe, very very safe, compared to space travel. We have a long, long way to go before we can say that we have learned to launch things into orbit safely.

Regarding the Proton: It is launched from the Baikonur Cosmodrome. If you want to place a vehicle into a 51.6 degree inclination orbit, that is a great location. It can launch 22.8 tons to a low Earth orbit with such an inclination. (BTW, that means 90 launches to achieve your 2000 tons. More on this later.) The Proton can only launch 1/4 that mass to geostationary transfer orbit. Baikonur is a lousy launch site for sending vehicles beyond low Earth orbit. The Cape, with a latitude of 28.5 degrees is pretty close to ideal. The ideal orbital plane for going to the Moon or other planets is the ecliptic plane, or an inclination of 23.4 degrees. (The ideal orbit of course has to have the correct right ascension of ascending node as well as the right inclination.) One last thing about the Proton: It is a Russian launch vehicle. The US government has this irrational desire to have a US launch capability.

Regarding the Falcon 9: It is still zero for zero. Talking about Falcon 9 is counting the chickens before the eggs have been laid.

Regarding Ares V: No money has been allocated for Ares V. All work to date (soon to be canceled) was on the Ares I. Work on Ares V was not to start until 2014 or so. There is a huge difference between pretend out-year budgets and allocations.



The reason LEO rendezvous was ruled out for Apollo was not just the cost of the launches. That was a small part of the picture. LEO rendezvous would have entailed rather large logistical, training, on-orbit assembly, and operations costs.

 

[mgb_phys]

Ariane 5 is doing rather well - it just reached 50 launches with only one catastrophic ooops.

 

[hamster143]

- Yes, I'm comparing apples and oranges. That's precisely my intention: to demonstrate that it's cheaper to use existing, reliable launchers than to develop new, unreliable ones from scratch.

- Protons' track record for the last ten years is 4 failures (5%) out of 80 launches. I am quite sure that it's a lot better than what Ares V with its $20 billion development costs and $1 billion incremental costs can expect during the first ten years of operation.

- Protons are used for unmanned missions. Manned missions are conducted using closely related Soyuz launchers. Russians haven't lost a single astronaut since 1971.

- Should we delay our space program by 10 plus years and spend tens of billions of dollars on Constellation, because we lost our own expendable launch capability, and we're to proud to collaborate with Russians?

- Falcon 9 is scheduled to fly in 3 days.

 

[Cotton_Sorbet]

I think the general consensus of smaller rockets and more frequent launches is the wrong way to go about it.
I get that smaller rockets need less powerful engines, which are easier to manufacture in principle than larger ones; they're easier to handle ie move from production to launch site and prep for launch, ect., than bigger rockets and they don't represent much of an expendature per rocket (so if one fails its not a huge drain on your resources).
However, to get a small rocket that will make it to orbit requires efficient engines, ie complicated ones with many moving parts that take a great deal of man hours worth of skilled labour to check for every flight, but you save on fuel and transportation issues on the ground.

This doesn't make sense!
Fuel is cheap, sheet steel is cheap; the expensive bits on your spacecraft are your engines and amortising the RnD required to develope it. If you can cope with much less efficient engines (ie fuel that is pressure fed instead of having your own (very expensive) mini gas turbine engine to compress it into the combustion chamber of your rocket), you end up having to pay a great deal less in their RnD and their manufacture, for the amount of stuff you get into space per launch.
As for handling, as it turns out there is a very large industry already existing that is perfectly made for the job of cheaply manufacturing and arbitrarily moving huge objects; the shipping industry. Routinely ships weighing hundreds of thousands of tonnes are manufactured very reliably and at comparatively very small cost compared to aeronaughtical manufacturing, where efficiency is the driving factor.

The rocket I am describing has already been designed and had extensive research put into its practicality; the Seadragon would have been NASA's next step from the Saturn V if not for the Vietnam war.

It was to be capable of 550 tonnes to LEO for $300 million (1962 -> ~2.2 billion in 2010), which equates to around $4,000 per kilogram in modern money. However, a great deal of this was from amortising RnD, which would be much cheaper today, since Computational Fluid Dynamics has advanced so much over the past 50 years.

In essence, bigger is better. Governments and people in power have a short attention span. A launch system that gets you thousands of tonnes into orbit for a half dozen launches is therefore more versatile than one that needs hundreds to achieve the same goals, since the hundreds of launches (appart from being more expensive) take longer to do and require a greater effort including much more manpower to produce.
Besides, bigger payloads lend themselves to more abitious manned projects, which is the direction that NASA should be going in; science is easily done with unmanned probes, but they're not very inspirational. A giant, manned colonisation and exploration of the solar system would do a great deal of good towards making more young people interested in the Sciences and Engineering, as well as all the massive potential benefits that come from an eventually self-sustaining expodition into the nearby parts of the solar system.

(For details on Seadragon, see;
http://www.astronautix.com/lvs/searagon.htm )