The decision was made fifty years ago this month.
Historically, the decision was a disaster, from the standpoint of making the effort sustainable, though it’s what won the race. Unfortunately, it was inevitable once it became a race to the moon and back. There was simply no time to develop the LEO infrastructure that von Braun and others wanted to put into place that would have obviated the need for the Saturn V. And it created a myth — that we can’t explore without such a vehicle — that haunts us to this day.
LOR makes too much sense. The EOR approach they wanted would’ve landed the Apollo capsule on the moon, including all of the unnecessary (for a lunar landing) weight of the heat shields, parachutes and propellant needed to return to Earth. That would’ve been incredibly stupid. The beauty of LOR was that it greatly reduced the mass you’d need to launch to just within the capabilities of a Saturn V.
However, doing EOR to assemble the vehicle and then LOR for the actual landing would’ve meaned that the Saturn V might not have even been needed to land on the moon. You might’ve been able to use Saturn IBs (2 or 3) to launch the separate pieces, dock to put them together and then fly to the moon.
There was simply no time to develop the LEO infrastructure that von Braun and others wanted to put into place that would have obviated the need for the Saturn V.
That’s another myth, we didn’t need any LEO infrastructure to obviate the need for Saturn V.
That’s another myth, we didn’t need any LEO infrastructure to obviate the need for Saturn V.
For a sustainable program you would.
Von Braun was notes to have said that the entire concept of LOR would give us a “Kilroy Was Here” mindset (if you don’t know what the Kilroy statement means google it_ that would make it easy for politicians to cancel the program after the first few successful missions…..
He was right.
For a sustainable program you would.
No you wouldn’t. Sustainability is mainly a function of launch prices. LEO infrastructure doesn’t figure into it. Infrastructure would likely be a result of a sustainable program however.
I agree with Larry that an EOR/LOR approach would’ve made more sense. Keep the launchers small enough to be useful for other missions, and flying regularly to spread fixed costs over more missions. Have in-space infrastructure (like depots) that could enable missions (manned and unmanned) to a wide range of destinations, but use LOR to avoid having to carry everything to the lunar surface and back.
~Jon
They didn’t choose LOR.. they chose a bastard hybrid with Apollo hardware. Remember “Lunar Orbit Rendezvous” originally meant just that: send all the hardware to lunar orbit, then send the crew to rendezvous with it. LOR was the small booster plan and small capsule too. It was the best kept secret of the space race, because if the Russians had figured it out earlier and scuttled their own big booster program, they would have beat the US to the Moon.
Trent that is not right. The design of the CM, SM, and LEM was not fixed at the time of the final studies on the Saturn. It was Von Braun that added the fifth engine on the first stage because he did not believe Gilruiths number coming out of JSC.
The only requirement for the Saturn Vehicle as it came down from headquarters was:
98,000 lbs to TLI
Get it done safely.
Those were the only directives from headquarters.
By the time of Apollo 17 the folks at MSFC upped that number to 115,000 lbs to TLI.
The Russians were working on a version that would have used the Proton after the loss of the N-1.
Umm.. that sounds like you’re agreeing with me, not disagreeing.
The debate about LOR/EOR/Direct was over whether to use rendezvous and where. In the end, all camps lost and a compromise was reached: all the hardware being launched together (like Direct) but with a single rendezvous in lunar orbit, after the primary mission had been achieved (“and return them safely to the Earth” coming after). Was that decision made in 1962? Hell no. That mission mode came long after and it was only because the direct camp refused to yield.
Had LOR actually won the battle and been “selected” in 1962, as history and the linked article would have us remember, the astronauts would have flown to the Moon in a Gemini and landed on it with open-cockpit single person landers that were waiting in lunar orbit.
This celebration of NASA actually making a decision (what a glorious day that would be) is bunk.
ref: http://www.munseys.com/diskone/chariot.htm#6
I don’t buy it. I have read Hubolt’s proposal and he was equally ok with EOR as long as the part that went down to the Moon was a minimal system.
That is the essence of LOR.
Dennis, you have to read between the lines. Particularly the part where Houbolt says, “We don’t need any Houston empire to do it.”
That was Langley saying, just give us the money and we can do it with Gemini. There’s no other interpretation that makes sense — you couldn’t do Apollo without Houston.
The essence of LOR is rendezvous in lunar orbit.. a lunar orbit rendezvous if you will. Talking about LOR vs EOR is irrelevant if LOR subsumes EOR.
“There was simply no time to develop the LEO infrastructure that von Braun and others wanted to put into place…”
I don’t know about that. If we had tried to put up that stupid wheel space station, we’d probably still be trying to put up that stupid wheel space station…
That “stupid wheel space station” was brilliant, and we’ll still have it — sooner or later. Microgravity kills.
Not so much. Imagine a world where the Saturn V was never mothballed and total spending was the same as our actual history. As it turns out we ended up spending about $200 billion on the Shuttle program, about $1.5 bil per flight. The Saturn V cost about $1.2 bil (in 2012 dollars) to fly.
So consider, by 1985 (which is nearly 30 years ago now) NASA had expended as much as it would have cost to fly 50 Saturn V missions on the Shuttle program. And this is entirely separate from the Apollo program. We could have launched 20 Saturn V’s and had $30 billion dollars of cold hard cash to use for developing the hardware of that “stupid wheel space station”. 20 Saturn V’s is about 2400 tonnes to LEO, which is more than the weight of a WWII era Destroyer. It would not only have happened, it would have been easy. And who knows what we could have done with all of the Apollo program money aside from that.
Robin,
Yes, it could have been used to build a ring station if NASA wanted to waste resources on one. But its real value would have been in using it to build a base on the Moon as well as fly missions to Mars, Venus and NEOs.
The Saturn V basically gave humanity the inner Solar System and we just threw away in the mistaken belief that NASA could deliver on CATS with the Shuttle.
I still haven’t heard the right answer. They should have focused on an SSTO lunar lander that could start in LEO. Size it to the biggest rocket at the time rather than develop the Saturn V. Send it up dry and fuel it in LEO. I’m guessing they would use the Saturn 1B.
This lander would by definition be reusable. They could just leave it in LEO until reuse on a new mission. We could then visit the moon as many times as we liked for a lot less cost.
Oh yeah? Where are you refueling?
Assuming aerobraking for return:
Just in LEO? 9137 m/s.
LEO and the Lunar Surface? 6247 m/s.
LEO and EML1? 4710 m/s.
LEO and EML1 and Lunar Surface? 3770 m/s.
Just gotta crack that chicken egg.
There is a small weight savings in not taking a re-entry craft all the way to the moon and back, requiring another rendevous in Earth orbit to get in an atmospheric return capsule. A reusable, refuelable lunar ascent stage would save weight over multiple missions, but of course it would get filthy and reliability would probably degrade badly.
One major change in flight mode would be launching most of the equipment unmanned on a low-energy path to the moon, which as I recall lets you deliver about twice the payload (taking many months to get there.) If you combine these methods, everything would arrive in place in lunar orbit and then the crew would take the direct path in something similar to the orbital module of a Soyuz.
Forget the weight savings.
Michael Collins from Apollo 11 brought this up in one of his books. The big problem with landing the reentry module on the Moon and then directly blasting off from the Moon to return to Earth is, how do you land the fine thing?
His guess is that the Direct Ascent lunar vehicle would be this stack as tall as the Mercury/Atlas, and how do you land such a thing tail first on the Moon without having it tip over? If your reentry vehicle is on top of the stack, how do you see out the window to guide the stack to a Moon landing? If the reentry vehicle is on top of the stack, how tall a ladder does the crew need to actually walk on the Moon?
Before you think I am silly, look around the Web for some conceptual drawings of Lunar Gemini to see what I mean.
His guess is that the Direct Ascent lunar vehicle would be this stack as tall as the Mercury/Atlas, and how do you land such a thing tail first on the Moon without having it tip over?
That’s silly. DC-X did it just fine, until the landing-gear accident. And that was in a one-gee field.
Silly? Were they landing the DC-X tail first on the craggy lunar surface and with how much horizontal slope?
The LM had a lot of design margin in it with respect to downward visibility, stability on its landing pads. Think of Armstrong’s “cross country flight” when the intended landing patch was full of boulders and he was making the ground controllers pucker up at each end in his search for “another airport.”
I suppose, we could have followed the Russian plan of preceding the landing with a robotic rover that could 1) pick out an LZ to within the narrower margins of the Direct Ascent vehicle, 2) served as a “runway” beacon so they wouldn’t have brought the thing down in the Apollo 11 boulder patch. But there were a lot of unknowns regarding the uniformity of the lunar soil, and how could they know that they wouldn’t guide in the Direct Ascent vehicle and have it tip on its side after making ground contact?
landing the reentry module on the Moon
Is anybody suggesting that?
Oh, I think you’ve mistaken my suggestion. Use the same hardware, but leave the command module in Earth orbit because it doesn’t actually have anything to do on a lunar mission. The crew makes the whole trip in the lightweight ascent stage, drawing power from the service module on the trip out and back. The lunar deorbit, landing, and ascent are exactly as before (abandoning the descent stage on the lunar surface), but the LM makes the rendevouz with the service module alone (minus a command module), and flies back. The only added burn is Earth orbit insertion instead of direct entry, but the weight saved by not flying the command module on the entire trip still leaves you with a lighter stack.
If the ISS was in a better orbit for lunar and planetary missions, it would be the same as using it as a departure and return point, so the re-entry capsule wouldn’t even be part of the mission’s budget.
Were they landing the DC-X tail first on the craggy lunar surface and with how much horizontal slope?
No, DC-X didn’t have enough delta-v to reach the Moon. That would have been the DC-1. What’s your point?
The LM had a lot of design margin in it with respect to downward visibility, stability on its landing pads. Think of Armstrong’s “cross country flight” when the intended landing patch was full of boulders
The downward visibility was adequate, not great. To get a better view, the pilot turned the LM on its side.
I’d don’t downward visibility still such an important design parameter because we have tiny cameras and flatscreen 3-D displays now. A few bug-size cameras on the bottom of a Dragon and the pilot would have a better view than the Apollo astronauts.
We also have laser range finders so each landing leg could adjust its length so that the craft always touches down on the level, almost regardless of the slope of the terrain.
One of the mysteries of the lunar landings is that the automated landing system always picked a rocky patch and the astronaut had to manually fly to a nearby clear area every single time. It’s like test pilots aren’t content to land on the moon in autopilot or something. ^_^
If you leave the command module in LEO you need to bring up enough fuel to brake out of LTO back into LEO, or else bring along an aerobrake. If you bring along the aerobrake you may as well just ride it all the way down and what’s your CM for?
There are, what, eight phases? Earth surface to LEO. LEO to LTO. LTO to lunar orbit. Lunar orbit to lunar landing. Lunar takeoff to lunar orbit. Lunar orbit to LTO. LTO to LEO. LEO to earth surface. Some of these could be combined–the craft could launch directly from Earth surface to LTO, for instance, or, like Apollo, go directly from LTO to earth surface on the way back.
If you were really sure about your hardware, you could do a semi-Apollo mission by: Earth surface to LTO (direct insertion), LTO to lunar surface (leaving the command module in LTO. It would have to do a funky burn or gravitational flyby so that its new orbit would come close enough to the moon on the next swing by). Lunar crew spends ten days (maybe longer, depending on the CM’s orbit) on the moon before boarding their ascent stage which does a direct insertion to LTO and dock with the command module. If you were being Apollo-ish you’d let everything burn up during reentry, if you were into reuse you’d leave the CM (now more a habitation and docking module) and LM in LTO and send up cargo vessels to refuel and resupply and replenish for the next trip.
How do you get lower energy from LEO to the moon than the Holman transfer? I don’t see any other objects in the area for a gravity assist.
For a serious plan to return to the moon, I’d assume refueling somewhere in cis-lunar space. As many as 3 vehicles and 2 way stations:
– Earth to LEO
– LEO station
– LEO to cis-lunar space
– cis-lunar station
– cis-lunar space to lunar surface.
Hohmann transfer from LEO to lunar orbit is around 4 km/sec (3.13 km/sec at the earth end, .83 km/sec at the moon). I wouldn’t be surprised if there were some 3-body trickiness that you could use to reduce the .83 km/sec portion, but I’d think the 3.13 km/sec from LEO is going to be pretty firm.
It’s been a while since I looked at the various Cycler proposals, but they may make sense if there is ever a time when rocket propulsion is still fundamentally chemical but there is a significant amount of traffic between the earth and the moon.
Yes, there are some very low energy paths that take advantage of the three-body problem. In fact, from a Lagrange point you can go just about anywhere in the solar system for almost no delta-V at all.
Interplanetary Transport Network wiki
Several lunar missions have used such paths.
3 body mechanics and Lunar assist can help parking at or EML1 or 2. But not so much with leaving with LEO. You’re stuck with about 3.1 km/s departing LEO.
I used.
LEO to LTO = 3107
LTO to surface = 3140
I’m told we can almost build an earth to LEO ssto which would require a delta v of about 10 km/s.
LEO to LTO = 3.107 + to surface = 6.247 + back to LTO = 9.387 km/s. So it may be doable. LTO to surface x 2 is definitely doable. So you refuel and transfer crew at LTO.
it would get filthy and reliability would probably degrade badly.
So does my truck. Does that make it a bad idea?
Hmm. Either my calculator or my geometry is wrong. I get for a simple LEO to lunar orbit Hohmann a burn of .83 km/sec at the high end. From lunar surface to lunar escape velocity + .83 km/sec I get 2.52 km/sec. That’s about .6 km/sec difference between your number and my back-of-the-envelope one. I don’t see acceleration losses being able to account for much of that. Maybe there’s an intermediate lunar orbit in there somewhere?
Daver, there’s an addon for terminal guidance and landing.. it’s Apollo derived.
LTO with a 300 km perigee and 378000 km apogee is moving about .19 km/s at apogee, the moon’s moving about 1.02 km/s, so Vinf is about .83 km/s.
Hyperbola velocity is sqrt(Vesc^2 + Vinf^2). Plugging lunar escape velocity of 2.38 km/s you get
sqrt(2.38^2 + .83^2)km/s which is 2.52 km/s.
How’d you get 3.14 km/s?
Three body trajectories use the Sun, though not for a powered flyby obviously. They use it to raise perigee, so that you only have to do your (slightly more expensive) TLI, not an insertion burn. If you want to minimise delta-v, and consequently maximise the payload you can deliver with existing upper stages, then you could choose L1/L2.
I’m not sure how much different that’s going to make, assuming you’re using a chemical rocket to land on the moon. Lunar escape velocity is 2.38 km/sec, Lunar escape to Hohmann transfer is 2.52 km/sec (take these numbers as provisional–I don’t know why they don’t agree with Trent’s). L1 may be a bit easier to reach than lunar orbit, but if you’re landing (and not selenobraking) there doesn’t appear to be much in the way of energy savings.
L1 may be a bit easier to reach than lunar orbit
Yeah, that would be an important benefit, because it makes the constraint of existing upper stages less severe. Overall efficiency isn’t the most important measure if the payload capacity from end to end is too small.
, but if you’re landing (and not selenobraking) there doesn’t appear to be much in the way of energy savings.
Even though savings aren’t the main point, there are actually substantial savings. 3.2 km/s from LEO to L1/L2 + 2.5 km/s from L1/L2 to the moon vs 4.2 km/s from LEO to LLO + 2 km/s from LLO to the moon.
It’s like test pilots aren’t content to land on the moon in autopilot or something.
With 18 dracos and 8 superdracos (not all required) the pilot of a red dragon is always going through a computer interface. Landing will probably descend automatically to a hover height setting. The computer will override hover when the fuel gets down to a certain point if the pilot hasn’t yet hit a land from hover button. Piloting a red dragon on landing will probably be so simple it doesn’t require much training at all. Tell it with a joystick or martian GPS where you want to go and it goes there assuming you have the fuel.
Ken,
Its also important to remember its unlikely any astronauts will be making the first landings as a site as in the days of Apollo. Instead any future human landings on the Moon or Mars will come only after a rover has carefully checked out the landing site for any hazards. The rover will likely also place 3-4 beacons around the landing area for the Dragon to use as reference points. And of course it will track and film the landing.