Numerous times the argument has been made by “commercial space” supporters (on numerous websites) that any kind of an HLV is not needed for any purpose. No distinctions were made about this destination vs. that destination. It was superior to launch all payloads in Falcon 9 size increments (20,000 to 30,000 lbs) and use orbital assembly and orbital propellant depots to assemble whatever sized vehicle in-orbit was required. This provided (so it was said) greater flexibility and the very fact that so many launches would be required would lower cost dramatically. We can debate whether or not that argument is valid, but it will not change the fact that Musk is now advocating an HLV so large that (in Musk’s words) it will “make the Apollo Moon rocket look small”.

“In any case it is good news that SpaceX may take part in return to the Moon missions, presumably using the Falcon Heavy, especially since NASA has shown no interest in mounting such missions. Note also the time frame this would happen would be prior to 2025 since that is when the Mars missions would take place. So we could return to the Moon by the 50th anniversary of the Apollo missions!”

Let’s skip the “NASA has shown no interest in mounting such missions” part. The current administration has shown no interest in mounting lunar missions and imposed that point of view on NASA, which is not the same thing.

The more important point is your statement about “this would happen would be prior to 2025 since that is when the Mars missions would take place. So we could return to the Moon by the 50th anniversary of the Apollo missions!”

I do not want this to turn into an off topic back and forth about the “magic” of Space X. If you really believe that Space X is going to:
– Develop the Falcon Heavy, a BEO version of the Dragon vehicle and a Lunar Lander. Then use that hardware to fly a crewed lunar mission by 2019.
– While simultaneously developing an HLV that will dwarf the Saturn 5 and all the new habitation modules and Martian landers needed to begin building a Martian Colony by 2025.
– All on private money.

Nothing anyone can say is going to convince you otherwise.

So why don’t we just wait and see what actually happens

Bob Clark

Settlements on Mars are markets on Mars. And to get settlements on Mars, Mars needs to be explored, and there needs to be other markets in Space.

You get large launchers when there is more markets in space.
Or you will get large rockets when there is more traffic to space.
And this is exactly why NASA should not have focused on making a large launch vehicles- because inhibits NASA exploration of space.

What both Musk and NASA fail to realize is the focus should be towards establishing more markets in space. The degree NASA and Musk have ignored the Moon is evidence of this neglect.

I believe the first market in space will probably be the rocket fuel. NASA can start this market by building and using depots.

It’s very unrealistic to imagine exploring Mars without having fuel depots. And not a smart idea to not to use fuel depots if you exploring the Moon to find minable lunar water.
For lunar water to be mined, it has to be found and next one needs to establish a market for rocket fuel in space.
Now one can imagine the market of rocket fuel in space may be only market of lunar rocket fuel at lunar surface.
But this is not very workable. Because to mine lunar in profitable manner, one need to mine + 100 tons of water per year of time. And to mine more than 100 tons of water one needs a large demand for rocket fuel. And exporting from the moon is path to such a larger demand for lunar rocket fuel.

Having a lunar base with say 100 people living there would also be a sizable market for lunar water and lunar rocket fuel. But a lunar base with 6 people is not much of a market for water or rocket fuel.
Now sending 10 tons of lunar samples to earth per year, is by
itself also not much of market for lunar water or rocket fuel.
But it adds to the demand. But it not as significant as shipping lunar rocket fuel to lunar orbit.

Or if one has a tourist going to moon and using lunar rocket fuel at the lunar surface and get 10 tons per year. Then if shipping lunar rocket fuel to orbit which tourist can buy, then instead 10, the tourist is buying 30 tons- without any increase to tourist costs. Or having lunar rocket fuel available on the moon significant lower costs, but whether tourist buy rocket fuel shipping from Earth to lunar orbit or buys it shipped from Moon is about same costs. So no much difference to tourist where the rocket fuel is coming from, but big difference to lunar water miners.
And given enough time and enough rocket fuel sold, rocket fuel prices could be half their price. But 1/2 the price of rocket fuel will not make much difference to cost of lunar tourist
to get to Moon. It’s not as dramatic as simply having rocket fuel available at the lunar surface. Nor a significant as simply having rocket fuel available at lunar orbit- and/or having rocket fuel available at LEO.
Or the biggest affect of having cheap lunar rocket fuel will be the exporting of stuff from the Moon.
So bigger effect would be on cost shipping lunar samples to Earth, or shipping lunar water for going to Mars.

Because the major cost for tourist getting to the Moon when rocket fuel is available in space is the cost of leaving Earth.
BUT if there enough traffic leaving Earth, this larger amount of traffic will lower the costs of leaving earth. And with higher traffic one part of lower the cost will be to to make larger launch vehicles.

A vehicle with an LEO capacity of 70 to 80 metric tons (and capable of being launched 6 to 8 times per year) will do nicely to support a large scale effort to establish lunar mining capability. As Dr. Spudis has pointed out many times the Side Mount SDHLV would have filled that role very well. Sadly that window of opportunity has closed, but the Block I SLS can meet the requirements (note that even the Block II SLS – 130 metric ton version – while nice to have is not required).

I did not reference the ROMBUS design to either endorse or criticize it, only to use it to show the scale (actually the minimum scale) implied by Musk’s current musings. It is ironic that while his internet supporters have consistently derided the value of any HLV, he is now talking about a “Super” HLV wildly beyond anything being currently proposed elsewhere.

Thanks for the link to the Space Works study, it is an interesting presentation.

Check out Space Works’ huge interplanetary booster concept:

A Study of CPS Stages for Missions beyond LEO

http://www.sei.aero/eng/papers/uploads/archive/SpaceWorks%20CPS%20Study%20Final%20Distribution.pdf

Marcel

http://www.astronautix.com/lvs/rombus.htm –

Interesting.
So::
Gross mass: 6,363,000 kg (14,028,000 lb).
Payload: 450,000 kg (990,000 lb).
Height: 29.00 m (95.00 ft).
Diameter: 24.00 m (78.00 ft).

What I call pipelauncher which was somewhat large [30 meters in diameter],
could be used to allow this rocket to be launched from the ocean.
Since ROMBUS is using Hydrogen it’s overall density is low-
despite having mass of over 6000 tonnes.
In comparison, if had 24 meter diameter cylinder which 20 meter tall which which
filled with water, the water would weigh 9043 tonnes.
Or 24 meter cylinder filled with air in the water can displace 9043 tonnes
of water.
So instead 20 mete tall if make 60 meter tall. And put a cap on one end
of pipe, and let water in the other end, so the 40 meter of 60 meter length
is filled with water and leaving 20 meter of it filled will air.
Then, this would float vertically, and total weight it
could float is 9043 tonnes. Or it needs 9043 tonnes of total weight to
push the air below the surface.
So it would float this ROMBUS launch vehicle.

And if make pipelauncher have 30 meter diameter, then 20 tall would
float 14,130 tonnes.
Or floats more than twice as much mass as rocket or it needs less
10 meter of pipe length filled with air to float it.
And the air inside pipe will be depressing water less than 10 meters
under water, which also means the air pressure needs to be less
than 1 atm- 14.7 psi.
10 meter under water is 1 atm of pressure.

And if double the air pressure, it makes it goes up at 1 gee- it
accelerates at 9.8 m/s/s.
And continues this accelerate as long as there is twice this
pressure and/or you run out of the pipe length.
The “use” of pipe length is as exponential as the acceleration.
Or with 1 gee in second one falls 4.9 meter, 2 seconds, it’s 19.6 meter, and 3
seconds it’s 44.1 meters, and fours seconds it’s 78.4 meter.
So a 60 meter tall only gets about 3 seconds.
3 seconds is about 65 mph. So one have pipe length considerable
longer than 60 meter to get a speed faster than 100 mph.
But one could just launch it around 60 mph, and mainly using it as
a launch pad in the water, which gives the rocket a bit of push.

And giving a much smaller push at lift off is common with launch pads.
Whether it’s actually pushing a bit, or coming to full power and releasing.
Of course I am talking i much more than that, I am just as general principal
it’s already done to some extent. Though a Polaris sub launch, would be more
similar. Or more perhaps similar than that, a Sea Dragon launch.

I see billgamesh and Marcel have already answered part of the cost equation issue, but I will add a little more.

Mr. Musk does not specify even a preliminary design for this HLV which will supposedly dwarf the Saturn 5/SLS so it is not possible to evaluate a possible cost.

The Falcon 9 is a very middle line booster using very well understood technology and was heavily subsidized by the government. So even if you hypothetically accept that it was developed at an extraordinarily low cost, using it as a cost comparison to a new launch vehicle that Musk says would be on “a bigger scale than has ever been done before” and “would have to launch very frequently as well” is not valid.

Additionally while some “commercial space” supporters may actually believe Musk can develop such a vehicle cheaply (and on private money) that is not the argument that they have repeatedly made. That argument (unless history is to be re-written) was that any HLV is completely unnecessary because all that is required are lots of flights of the Falcon 9 (with lots of rendezvous/docking/berthing and fuel transfers). Now that is not what Musk is saying. That was the (I think very clear) point of my post.

But I’ve long suspecte that the ISS extension is really a ruse by the Obama administration to prevent NASA from having appropriate funding for beyond LEO missions in the 2020s.

Marcel