Author Topic: Spacex and the Moon?  (Read 14580 times)

Offline corneliussulla

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Spacex and the Moon?
« on: 07/31/2011 10:05 AM »
In today Sunday Times Newspaper in the UK. There is an interview with Elon Musk. In the interview he is asked about destinations beyond earth. To which he replies that

" he may soon have an announcement to make concerning moonflights"

I wonder has the Falcon Heavy dragon combination the capability to land on the moon? What sort of additional functionality would they need to land. Could the Dragon be used as a lander and return astronauts to Earth ?

Would they need a space habitat as well to do flyby mission. Would they require a 2nd stage or could they use the middle tank to inject in Lunar orbit

The dragon can hold 4 astronauts without space suits. 7 if they use the cargo bay. But i expect if they are thinking of flying 7 people in a moon flyby they would need space suits and extra space for the journey.

Once again Elon leads NASA on a shoestring budget showing the ineptitude of the Government body. NASA spend $8 bill developing Orion to go nowhere. Elon spends $300 mill on Dragon as is talking return to the moon.

Offline rklaehn

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Re: Spacex and the Moon?
« Reply #1 on: 07/31/2011 10:19 AM »
In today Sunday Times Newspaper in the UK. There is an interview with Elon Musk. In the interview he is asked about destinations beyond earth. To which he replies that

" he may soon have an announcement to make concerning moonflights"

Maybe a free return around the moon trip using a falcon heavy and a dragon.

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I wonder has the Falcon Heavy dragon combination the capability to land on the moon?

Not with one launch.

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What sort of additional functionality would they need to land.

A lander.

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Could the Dragon be used as a lander and return astronauts to Earth ?

You might be able to land a second generation dragon (with the powered landing system) on the moon using a crasher stage approach. You use an expendable stage to decelerate the dragon, and just do the last 100m/s or so using the dragon propulsion system. But you can not launch from the moon again. It has enough thrust, but not nearly enough delta-v to make low lunar orbit.
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Offline Phillip Clark

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Re: Spacex and the Moon?
« Reply #2 on: 07/31/2011 10:32 AM »
Whilst I agree that the Falcon series can be extremely useful for a manned lunar programme, it will always need multiple launches.   Now I know that ISS has been constructed successfully with multiple launches, but I would feel safer if the number of launches for a lunar (or beyond) mission were to be minimised.   That is why on a separate thread I voted in favour of a Heavy Lift Launch Vehicle.

It is interesting that the Chinese are now talking about the preliminary studies for a Heay Lift Changzheng vehicle in the Saturn-5 class of payload capability (again, the papers are on a separate thread in the Forum).   Previous discussions had centred around multiple CZ-5 launches, although that might have been simply echoing back western speculations.

Offline corneliussulla

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Re: Spacex and the Moon?
« Reply #3 on: 07/31/2011 10:50 AM »
rklaen as far as i undersand you need 1870m/s of delta v to land and same to return to Lunar orbit. I wonder if the Cargo dragon was fitted tanks and landing legs could this provide enough fuel to get the required delta v. Maybe the cargo module could be split with two sets of tanks in such a way as to allow the legs and empty tanks to be left on the surface

Offline rklaehn

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Re: Spacex and the Moon?
« Reply #4 on: 07/31/2011 11:04 AM »
Whilst I agree that the Falcon series can be extremely useful for a manned lunar programme, it will always need multiple launches.   Now I know that ISS has been constructed successfully with multiple launches, but I would feel safer if the number of launches for a lunar (or beyond) mission were to be minimised.   That is why on a separate thread I voted in favour of a Heavy Lift Launch Vehicle.

All that is needed for a moon landing is a single docking in low lunar orbit or EML1/2 to get the crew from the dragon to the lander.

Even with a single launch heavy lift mission you need at least one docking (the ascent stage has to dock with the dragon in LLO on the way back) unless you plan for direct return from the surface of the moon.

So you propose to spend tens of billions of dollars to build a heavy lift launcher to reduce the number of autonomous dockings at the staging point from two to one?

Comparing the assembly of the ISS with thousands of hours of spacewalks with a simple docking of a lander and a dragon that can be done completely autonomously is misleading.

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It is interesting that the Chinese are now talking about the preliminary studies for a Heay Lift Changzheng vehicle in the Saturn-5 class of payload capability (again, the papers are on a separate thread in the Forum).   Previous discussions had centred around multiple CZ-5 launches, although that might have been simply echoing back western speculations.

It's not surprising that a centrally planned space program that is done mostly for reasons of national presige will come up with the biggest possible launcher. That does not mean that this is the best approach. The russians copied the space shuttle with buran. That does not mean that the space shuttle was the most economical way to go to space.
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Offline rklaehn

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Re: Spacex and the Moon?
« Reply #5 on: 07/31/2011 11:11 AM »
rklaen as far as i undersand you need 1870m/s of delta v to land and same to return to Lunar orbit.

That is correct.

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I wonder if the Cargo dragon was fitted tanks and landing legs could this provide enough fuel to get the required delta v. Maybe the cargo module could be split with two sets of tanks in such a way as to allow the legs and empty tanks to be left on the surface

You could modify a cargo dragon as a lander. Remove the heat shield, add more (external) propellant tanks, add legs. But that would be a completely new spacecraft that reuses some parts of dragon such as the pressurized section and the new "super draco" engines.

Spacex is building a "toolkit" of engines, avionics, life support systems etc. And most of the people that developed these subsystems are still with the company. So I think it wouldn't be that hard for spacex to assemble the parts in this toolkit in a different way to build a lander.
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Offline corneliussulla

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Re: Spacex and the Moon?
« Reply #6 on: 07/31/2011 11:35 AM »
Well Falcon Heavy gets around 53Tonnes in LEO. That equates to about 19 Tonnes in LLO. Now to land the full 19 tonnes on the moon would require about 7 tonnes of Fuel if Dragon 2+ had ISP of 350. To get back  to LLO wstarting with full 11tonnes would require 4.6 Tonnes of fuel leaving us with 6.4 tonnes in orbit. LLO to LEO  requires a delta v of 1300 m/s so we would require to burn another 2.2 tonnes leaving us 4400Kgs in LEO. Dragon mass 4200KG.


It may also be posible to leave some mass on Moon giving us an extra 500kgs - 1000kGS in LEO

So it may be possible to do a direct return to earth using a dragon and a variation of the Cargo hold to carry extra fuel. Now that would be an exciting mission

Offline ugordan

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Re: Spacex and the Moon?
« Reply #7 on: 07/31/2011 11:41 AM »
Well Falcon Heavy gets around 53Tonnes in LEO. That equates to about 19 Tonnes in LLO.

Wrong on two accounts. The throw weight to TLI would be about 13 tonnes, not 19 tonnes. 19 tonnes to GTO maybe.

Second, it most certainly does not mean 19 tonnes in LLO, to enter LLO from a TLI trajectory requires a sizable burn so the usable mass in LLO will end up being even less than 13 tonnes.

Offline rklaehn

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Re: Spacex and the Moon?
« Reply #8 on: 07/31/2011 11:48 AM »
Well Falcon Heavy gets around 53Tonnes in LEO. That equates to about 19 Tonnes in LLO.

Nope. Much less. Since the falcon heavy has only a kero/LOX upper stage it can only get 19t to GTO. You are lucky go get 12t to LLO using a fast trajectory. You might be able to get 15t to LLO using a belbruno trajectory, but that is only viable for unmanned payloads since it takes >90 days.

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Now to land the full 19 tonnes on the moon would require about 7 tonnes of Fuel if Dragon 2+ had ISP of 350. To get back  to LLO wstarting with full 11tonnes would require 4.6 Tonnes of fuel leaving us with 6.4 tonnes in orbit. LLO to LEO  requires a delta v of 1300 m/s so we would require to burn another 2.2 tonnes leaving us 4400Kgs in LEO. Dragon mass 4200KG.

You won't get 350s Isp out of NTO/MMH. 320 is more likely. And 4200kg is the empty mass of a dragon. You need more than that for a realistic mission. So you do need two launches unless you want to use something radical like an open lander.
http://www.retro.com/employees/gherbert/Space/LunMil/lunarM.html

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It may also be posible to leave some mass on Moon giving us an extra 500kgs - 1000kGS in LEO

So it may be possible to do a direct return to earth using a dragon and a variation of the Cargo hold to carry extra fuel. Now that would be an exciting mission

A free return lunar flyby would be exciting enough, and it would actually be possible using a single falcon heavy.
« Last Edit: 07/31/2011 11:49 AM by rklaehn »
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Offline corneliussulla

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Re: Spacex and the Moon?
« Reply #9 on: 07/31/2011 11:49 AM »
Fair enough, no single launch Falcon Heavy to Moon surface then. Oh well might be done with a falcon 9 and a falcon Heavy then. Definetly two falcon Haevies.Total cost $200-300 mill. 4 people on Moon surface. I wonder what the market size for 3 days on the moon at $100 mill a pop is. Could be in the 100's

Offline corneliussulla

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Re: Spacex and the Moon?
« Reply #10 on: 07/31/2011 11:58 AM »
Just done the calculations

If you have ISP of 350 (like merlin in vacuum). Then 53 tonnes in LEO will give you 16 Tonnes in LLO.

If however you have an engine like Raptor with ISP 450 you get 21 Toones in LLO. which makes a dragon direct to moon surface withion realms of possiblity

Offline ugordan

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Re: Spacex and the Moon?
« Reply #11 on: 07/31/2011 12:01 PM »
Just done the calculations

If you have ISP of 350 (like merlin in vacuum). Then 53 tonnes in LEO will give you 16 Tonnes in LLO.

I'd like to see that calculation.

Offline corneliussulla

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Re: Spacex and the Moon?
« Reply #12 on: 07/31/2011 12:07 PM »
Well i used this Delta V calculator

http://www.strout.net/info/science/delta-v/

and this table of delta vs required to move around inside earth moon system

http://en.wikipedia.org/wiki/Delta-v_budget#Earth.E2.80.93Moon_space

Offline ugordan

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Re: Spacex and the Moon?
« Reply #13 on: 07/31/2011 12:14 PM »
Actual numbers? What is the delta-V you input for going from LEO to LLO, the full mass and dry masses? Does your dry mass take into account the 2nd stage dry mass? This is required at least for the TLI portion of the trajectory.

Also, minor nit - MVac can't do 350 s Isp, it's closer to 340. It's a gas generator engine.
« Last Edit: 07/31/2011 12:15 PM by ugordan »

Offline corneliussulla

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Re: Spacex and the Moon?
« Reply #14 on: 07/31/2011 01:51 PM »
53 tonnes Full mass gives you 21 Tonnes dry mass in LLO if ISP 450. Delta V 4040 m/s from LEO to LLO.  Thats raptor class engine. Regards Merlin 342 ISP. Thats true of old Merlin but maybe upgraded one will be able to do a bit better.

Using ISP 350 you get around 16tonne dry mass in LLO.

So dry mass needs to include 2empty 2nd stage plus Dragon and Modified Hold to include landing propellant. With 21 Tonnes it may be enough to get dragon down and back to LEO. 16 Tonnes:- no mission.

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