Moon mission today - Dragon & Mars hab

GW Johnson · 2016-06-01 09:45:06

I would remind everybody that you only need to solve all these difficulties with giant launch rockets if you insist on flinging large payloads directly into interplanetary trajectories.

If you assemble your large payload out of smaller pieces in LEO by docking, then you can launch these pieces with the rockets and infrastructure that you have.

I have to ask the question: why solve the harder problem when you can solve the easier one?

GW

kbd512 · 2016-06-01 11:23:18

RobertDyck wrote:

So don't build separate service masts. Saturn V used a Mobile Launcher (ML), which was a platform with service mast mounted on the platform. Shuttle used a Mobile Launch Platform (MLP), no service mast on the platform at all. KSC removed the static service structure and rotating service structure from the launch pads, so the pad could be flexible to handle different launch vehicles. They expect the service mast to be mounted on the Mobile Launcher. But you don't need a separate tower for each booster. Just run a propellant feed hose from one single common mast to tanks for each stage/booster.

This problem has nothing to do with the service tower.

1. No infrastructure exists to deliver RP-1 to the pad SLS will use and the LOX storage capacity would have to be substantially increased. Not a showstopper, but this is not a simple re-plumbing job. It would require complete removal and replacement of the existing infrastructure.

2. They'd have to build a structure around the pad to deliver the propellants to the boosters because there's no more space in or on the mobile platform for the TSM's. It's a plumbing problem. There's nowhere to put the pipes.

3. I'm certain a structure can be built around the pad, but cost estimates were expensive, to put it mildly.

RobertDyck wrote:

Look at the service mast for Atlas V. It's a lot simpler. It's made of steel I-beams instead of truss because it tilts back before launch.

Not even close to comparable to the pad and services setup required for SLS, with or without liquid boosters. These pads also have RP-1 storage and pumping capability.

RobertDyck wrote:

SpaceX uses a truss structure, but their's isn't just a service mast, it's a "hard back" that lifts the rocket from horizontal to vertical. That's done when propellant tanks are empty. The hard back isn't strong enough to lift it when tanks are full. But it shows a truss can rotate back.
Service mast for a crew launch vehicle will require an elevator to lift crew to the capsule. But you don't need a service mast as huge as the one for Saturn V. And you certainly don't need a separate service mast for each booster.

Same answer as above. Both Falcon and Atlas are far smaller and less sophisticated rockets with simplified provisioning requirements. That is also a really good reason to use them whenever possible.

RobertDyck · 2016-06-01 11:35:40

The pads were heavily modified from Saturn V to Shuttle. Including removing infrastructure for RP1 for Saturn V first stage. Pad A was heavily modified from Shuttle to Falcon Heavy, including infrastructure for RP1. Pad B is being heavily modified from Shuttle to SLS. Rebuilding infrastructure for RP1 is not a show-stopper, and frankly shouldn't be as expensive as developing an advanced solid booster. And that's the alternative, either liquid booster or advanced solid.

You complain that SLS is useless. Then claim any work necessary to make SLS can't be done. You claim it has to remain in a useless configuration to support your claim that it's useless. Circular argument. Go away.

kbd512 · 2016-06-01 21:04:04

RobertDyck wrote:

The pads were heavily modified from Saturn V to Shuttle. Including removing infrastructure for RP1 for Saturn V first stage. Pad A was heavily modified from Shuttle to Falcon Heavy, including infrastructure for RP1. Pad B is being heavily modified from Shuttle to SLS. Rebuilding infrastructure for RP1 is not a show-stopper, and frankly shouldn't be as expensive as developing an advanced solid booster. And that's the alternative, either liquid booster or advanced solid.

Unfortunately, there's no funding left for further modifications to the pad infrastructure because the funding has ben appropriated for Orion and SLS development. The funding marked for refurbishment of the pad facilities at KSC is being used for that purpose and there is sufficient funding for that purpose only.

If Congress had allowed NASA to build the all-liquid solution they wanted, this would not have been a major problem. I also think SLS would be further along than it is now.

RobertDyck wrote:

You complain that SLS is useless. Then claim any work necessary to make SLS can't be done. You claim it has to remain in a useless configuration to support your claim that it's useless. Circular argument. Go away.

I guess it depends on the objective. If the objective is to spend a lot of money, then I think SLS has achieved that. If the objective is delivery of payloads that only a super heavy lift rocket can deliver, there will probably be some disappointment.

You keep posting counter-points to points that I have restated based upon NASA's own analyses and decisions regarding SLS. Believe whatever you want about SLS, but I seriously doubt it will survive the next administration.

RobertDyck · 2016-06-01 23:25:53

NASA announced they will build SLS block 2. They later stated they'll build block 2B instead of block 2. I've grudgingly accepted that. You claim NASA said they cannot build either. That's not what NASA's web pages about SLS state.

kbd512 · 2016-06-01 23:27:10

This really looks like a job best completed using a couple of space tugs like Lockheed-Martin's Jupiter / Exoliner.

- The Exoliner's cargo modules can be replaced with BEAM.

- BEAM would contain the life support and consumables for two or four astronauts for the transit to and from the moon.

- The Jupiter / BEAM stack would be mated to a RL-10 equipped upper stage for TLI.

- ISS is not required for mate / de-mate operations because Jupiter has its own robotic arm. If there's an issue with mating the RL-10 upper stage, the best place for that to happen is far away from ISS.

- The stack would then dock at ISS for crew transfer. All crews can embark and disembark from ISS, so there's no requirement for sending heat shield equipped capsules into deep space. If there's a functional issue with the tug or habitat, there's no need to send a lunar mission crew to ISS and there is some chance of the ISS crew correcting the problem.

- The mission can still be undertaken without using ISS for crew transfers. ISS merely provides the option of lander refurbishment and reuse.

- A separate Jupiter tug would pre-position Golden Spike landers in lunar orbit ahead of the astronauts. If there's an issue with delivering the landers to lunar orbit, there's no need to launch the other tug or astronauts.

- The two tugs dock in lunar orbit to transfer the astronauts to the landers, the astronauts execute their surface mission, return to orbit, and then both Jupiter tugs bring the astronauts and landers back to ISS for consumables resupply and refurbishment. More launches are required, but after the first mission some of the hardware may be refurbished and reused.

- The capsule doesn't have to be deep space capable, it just has to make it to ISS. That means DreamChaser, Dragon, Orion, Soyuz, StarLiner, X37, or whatever else happens to be available at the time can deliver the crew. No specially designed and equipped capsules are required.

- The tugs can also deliver consumables, spares, scientific equipment, habitats, and rovers, as required.

- The tugs provide redundant propulsion options for the crew to return to Earth. If one tug is disabled, the other is available as backup.

- SLS is not required, and thus the billions not spent on SLS can be spent on all the other required hardware. To actually land on the moon or Mars, unimportant and un-funded things like landers, habitats, and improved space suits are required.

You know, with Mr. Musk's rockets and capsules, Mrs. Hewson's space tugs, Mr. Sterns landers, and Mrs. Newmans space suits, we could do a lunar mission!

RobertDyck · 2016-06-02 00:01:08

Let's take a step back. Return to what this discussion is about. I want a human mission to Mars. I think most people on this forum want that, possibly everyone. Current plans with Orion just won't do that. NASA has no credible plans to send humans to Mars. At the Mars Society convention of 2002, I presented my mission architecture to send humans to Mars. My plan is a minor modification of Mars Direct, addressing a few weaknesses. NASA was concerned with a couple of them, and refused to adopt Mars Direct because of that. My plan would resolve them. So I would like to proceed. Some people on this forum also objected to any modification of Mars Direct, however that changed in recent years. I have tried to stick to Mars Direct as much as possible, to keep members of The Mars Society pulling together.

This discussion thread addressed one of those weaknesses with Mars Direct. And the problem that NASA's current plans will not make any progress what so ever toward Mars. In fact, current plans won't even land any human on the Moon. I proposed a solution to fix all that.

Congress wants SLS. Robert Zubrin wants Ares launch vehicle for Mars Direct, SLS block 2 practically is Ares. Ok, fine! Let's build SLS block 2.

But Orion is useless. We have Dragon and CST-100 and DreamChaser, for cargo we have Dragon v1 and Cygnus. And Japan is still launching their HTV once per year, Europe isn't launching ATV any more, but Russia has Soyuz and Progress. With all that, we don't need Orion. Both Dragon and CST-100 were competitors for CEV to send American astronauts to Lunar orbit and back, competitors against Orion. They would need a larger service module, but that's all. And Orion was selected partially because it had an air bag landing system to touch-down on land, and it's service module would use LCH4/LOX. Both those features have been deleted. So the key attributes of Orion are gone anyway, why stick with it?

I said launch a Mars surface habitat to the Moon, as Robert Zubrin and his partner stated to NASA in June 1990. But since there is an issue with operating the Mars ERV on the Moon, I suggested using an Apollo architecture. And using Dragon together with a well designed LM could be launched on SLS block 1. That will be completed, that's the version of SLS they're building now.

For my Mars architecture I waffled between hard wall habitat vs inflatable. In this discussion I talked about hard wall because that would match the Mars Direct habitat. Again trying to go with the politically correct solution for Mars Society members. GW Johnson argued for inflatable. Ok, but that requires a capsule for astronauts to ride down to Mars. And that descent capsule is not necessary for the Moon, so could create temptation to delete it, creating a difference between the Moon hab vs Mars. That could invalidate using the Moon as a dress rehearsal for Mars. And my architecture required the ability to access food of the surface hab in case of free-return.

But again, lets look at the big picture. If you destroy everything, you get nothing. You can't ride Red Dragon to Mars. It's just a capsule the size of a cargo van, no artificial gravity and no zero-G exercise equipment, and no recycling life support. You wouldn't make it to Mars alive. And it doesn't have any means to leave Mars. Robert Zubrin's argument was to design a mission to Mars, then use that for the Moon. Since some guys at NASA are obsessed with the Moon, this throws them a bone. Arguing for nothing but Red Mars on Falcon Heavy just ensures we get nowhere.

kbd512 · 2016-06-02 00:12:25

RobertDyck wrote:

NASA announced they will build SLS block 2. They later stated they'll build block 2B instead of block 2. I've grudgingly accepted that. You claim NASA said they cannot build either. That's not what NASA's web pages about SLS state.

NASA doesn't write cheques, Congress does. It's not about what I want or what I think, it's about what appropriations our representatives approve. If the appropriations for SLS are insufficient and therefore don't produce results, eventually Congress will cut off funding. I'm trying to tell you that the funding levels allocated for the upper stage and advanced boosters development is insufficient to produce certified flight hardware within the next decade.

Since we've already sunk so much money into SLS, I'd complete development of the rocket at this point. That said, if there's a requirement for a super heavy lift rocket, then just develop the super heavy lift rocket and be done with it. No more Block I, IA, IB, 2, 2B nonsense. To actually complete development in anything approaching a reasonable timeframe a lift capability target has to be set and something else has to give as it pertains to funding. To keep the Orion and SLS programs, Congress needs to allocate an additional $2B a year in funding or they need to cancel one. It really is that simple.

Snapping back to political realities here, neither The Hillary nor The Donald have any real interest in space exploration, unless it wins votes. To the best of my knowledge our space program has never rated more than passing mention in any presidential election. If either of these programs survive the next administration, it will be as a direct result of congressional and not executive approval.

RobertDyck · 2016-06-02 00:22:04

You posted an alternative while I was composing mine. At least you posted something. That is overly complicated. Yes, I prefer an MCP spacesuit. But the tug isn't necessary if you use ISS. You don't have to launch ISS because it's already there. And Lockheed-Martin will never launch their Exoliner on a SpaceX launch vehicle. We would have difficulty getting SpaceX to use SLS; the only reason it's possible is NASA considers it their vehicle, not property of any contractor. So you're stuck with Atlas V and their price.

And the primary point of this is to use the Moon as a stepping stone to Mars. If none of the equipment can be used for Mars, then it's useless. I don't see how your suggestion works for Mars.

RobertDyck · 2016-06-02 00:35:57

kbd512 wrote:

I'm trying to tell you that the funding levels allocated for the upper stage and advanced boosters development is insufficient to produce certified flight hardware within the next decade.

Contractors have already received more than enough funding. Corporate executives are just pulling the same shit they did during the Shuttle era.

kbd512 wrote:

To keep the Orion and SLS programs, Congress needs to allocate an additional $2B a year in funding or they need to cancel one. It really is that simple.

I've repeatedly asked to cancel Orion.

kbd512 wrote:

Snapping back to political realities here, neither The Hillary nor The Donald have any real interest in space exploration, unless it wins votes.

I'm not placing bets. Could be anyone. At this point Bernie Sanders could win. I'm told many Republican voters are looking at Gary Johnson. This election is unlike any other. Media keeps trying to support institutional candidates, while voters appear to want practically anyone that isn't institutional. Be prepared for more surprises.

kbd512 wrote:

If either of these programs survive the next administration, it will be as a direct result of congressional and not executive approval.

Could be true. How do we focus funding into SLS? Kill Orion without killing SLS? Finish block 2 or 2B; let's be honest, block 1 is useless. The mission plan I described here with Dragon and a new light-weight LM is the only thing that block 1 could be used for.

Tom Kalbfus · 2016-06-02 05:15:33

You won't get much money from canceling Orion.

RobertDyck · 2016-06-02 09:37:51

Looking up stuff kbd512 talked about.

Golden Spike lander...interesting, but only 2 crew members.

Exoliner

Tom Kalbfus · 2016-06-02 10:20:37

It gets confusing when NASA names things after planets. The Saturn V rocket could have sent a probe to Saturn, but it was never used in such a capacity. The Moon program was called Project Apollo, but it had nothing to do with the Sun, Apollo was the Sun god, not the Moon god, that would be Artemis I believe.

The movie Superman II had a Moon mission called Artemis in it, which the three supervillains then proceeded to wreck

Now this is interesting. Looks like a rocket with flyback boosters.

Tom Kalbfus · 2016-06-02 10:32:17

Getting back to brass tacks, I found this article on Yahoo.
http://www.universetoday.com/129173/sci … ons-water/
Scientists Identify the Source of the Moon’s Water

1 Jun , 2016 by Matt Williams

Over the course of the past few decades, our ongoing exploration the Solar System has revealed some surprising discoveries. For example, while we have yet to find life beyond our planet, we have discovered that the elements necessary for life (i.e organic molecules, volatile elements, and water) are a lot more plentiful than previously thought. In the 1960’s, it was theorized that water ice could exist on the Moon; and by the next decade, sample return missions and probes were confirming this.
Since that time, a great deal more water has been discovered, which has led to a debate within the scientific community as to where it all came from. Was it the result of in-situ production, or was it delivered to the surface by water-bearing comets, asteroids and meteorites? According to a recent study produced by a team of scientists from the UK, US and France, the majority of the Moon’s water appears to have come from meteorites that delivered water to Earth and the Moon billions of years ago.

For the sake of their study, which appeared recently in Nature Communications, the international research team examined the samples of lunar rock and soil that were returned by the Apollo missions. When these samples were originally examined upon their return to Earth, it was assumed that the trace of amounts of water they contained were the result of contamination from Earth’s atmosphere since the containers in which the Moon rocks were brought home weren’t airtight. The Moon, it was widely believed, was bone dry.
Screen-Shot-2013-06-03-at-11.15.28-AM-580x420.jpg
The blue areas show locations on the Moon’s south pole where water ice is likely to exist. Credit: NASA/GSFC

However, a 2008 study revealed that the samples of volcanic glass beads contained water molecules (46 parts per million), as well as various volatile elements (chlorine, fluoride and sulfur) that could not have been the result of contamination. This was followed up by the deployment of the Lunar Reconnaissance Orbiter (LRO) and the Lunar Crater Observation and Sensing Satellite (LCROSS) in 2009, which discovered abundant supplies of water around the southern polar region,

However, that which was discovered on the surface paled in comparison the water that was discovered beneath it. Evidence of water in the interior was first revealed by the ISRO’s Chandrayaan-1 lunar orbiter – which carried the NASA’s Moon Mineralogy Mapper (M3) and delivered it to the surface. Analysis of this and other data has showed that water in the Moon’s interior is up to a million times more abundant than what’s on the surface.

The presence of so much water beneath the surface has begged the question, where did it all come from? Whereas water that exists on the Moon’s surface in lunar regolith appears to be the result of interaction with solar wind, this cannot account for the abundant sources deep underground. A previous study suggested that it came from Earth, as the leading theory for the Moon’s formation is that a large Mars-sized body impacted our nascent planet about 4.5 billion years ago, and the resulting debris formed the Moon. The similarity between water isotopes on both bodies seems to support that theory.

Near-infrared image of the Moon’s surface by NASA’s Moon Mineralogy Mapper on the Indian Space Research Organization’s Chandrayaan-1 mission. Credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS

However, according to Dr. David A. Kring, a member of the research team that was led by Jessica Barnes from Open University, this explanation can only account for about a quarter of the water inside the moon. This, apparently, is due to the fact that most of the water would not have survived the processes involved in the formation of the Moon, and keep the same ratio of hydrogen isotopes.

Instead, Kring and his colleagues examined the possibility that water-bearing meteorites delivered water to both (hence the similar isotopes) after
“The current study utilized analyses of lunar samples that had been collected by the Apollo astronauts, because those samples provide the best measure of the water inside the Moon. We compared those analyses with analyses of meteoritic samples from asteroids and spacecraft analyses of comets.”

By comparing the ratios of hydrogen to deuterium (aka. “heavy hydrogen”) from the Apollo samples and known comets, they
determined that a combination of primitive meteorites (carbonaceous chondrite-type) were responsible for the majority of water to be found in the Moon’s interior today. In addition, they concluded that these types of comets played an important role when it comes to the origins of water in the inner Solar System.

These images produced by the Lyman Alpha Mapping Project (LAMP) aboard NASA's Lunar Reconnaissance Orbiter reveal features at the Moon's northern and southern poles in the regions that lie in perpetual darkness. They show regions that are consistent with having large surface porosities — indicating "fluffy" soils — while the reddening is consistent with the presence of water frost on the surface. Credit: Southwest Research Institute
Images produced by the Lyman Alpha Mapping Project (LAMP) aboard NASA’s Lunar Reconnaissance Orbiter reveal features at the Moon’s northern and southern poles, as well as the presence of water frost. Credit: NASA/SwRI

For some time, scientists have argued that the abundance of water on Earth may be due in part to impacts from comets, trans-Neptunian objects or water-rich meteoroids. Here too, this was based on the fact that the ratio of the hydrogen isotopes (deuterium and protium) in asteroids like 67P/Churyumov-Gerasimenko revealed a similar percentage of impurities to carbon-rich chondrites that were found in the Earth’s coeans.

But how much of Earth’s water was delivered, how much was produced indigenously, and whether or not the Moon was formed with its water already there, have remained the subject of much scholarly debate. Thank to this latest study, we may now have a better idea of how and when meteorites delivered water to both bodies, thus giving us a better understanding of the origins of water in the inner Solar System.

“Some meteoritic samples of asteroids contain up to 20% water,” said Kring. “That reservoir of material – that is asteroids – are closer to the Earth-Moon system and, logically, have always been a good candidate source for the water in the Earth-Moon system. The current study shows that to be true. That water was apparently delivered 4.5 to 4.3 billion years ago.“

The existence of water on the Moon has always been a source of excitement, particularly to those who hope to see a lunar base established there someday. By knowing the source of that water, we can also come to know more about the history of the Solar System and how it came to be. It will also come in handy when it comes time to search for other sources of water, which will always be a factor when trying to establishing outposts and even colonies throughout the Solar System.

Further Reading: Nature Communications

Last edited by Tom Kalbfus (2016-06-02 10:39:34)

kbd512 · 2016-06-02 15:26:26

RobertDyck wrote:

You posted an alternative while I was composing mine. At least you posted something. That is overly complicated. Yes, I prefer an MCP spacesuit. But the tug isn't necessary if you use ISS. You don't have to launch ISS because it's already there. And Lockheed-Martin will never launch their Exoliner on a SpaceX launch vehicle. We would have difficulty getting SpaceX to use SLS; the only reason it's possible is NASA considers it their vehicle, not property of any contractor. So you're stuck with Atlas V and their price.

The tug is not necessary if you use ISS? Non-sequitur.

If NASA is paying for Jupiter and Exoliner, then Lockheed-Martin really doesn't have any say-so over what launch vehicle it's launched on. The same applies to SpaceX launching Dragon on SLS. If NASA is footing the bill and the contractor wants money, they'll figure it out.

RobertDyck wrote:

And the primary point of this is to use the Moon as a stepping stone to Mars. If none of the equipment can be used for Mars, then it's useless. I don't see how your suggestion works for Mars.

The tugs are required to deliver cargo to Mars. The inflatable habitat modules are required for deep space transit. Large capsules that are too small to store the required consumables and too heavy to deliver are not required deep space transit.

RobertDyck · 2016-06-20 14:39:16

Did a little research. Skylab, Dragon, Orion, and CST-100 all use isogrid.
Wikipedia: Isogrid

The triangular pattern is very efficient because it retains rigidity while saving material and therefore weight. The term isogrid is used because the structure acts like an isotropic material, with equal properties measured in any direction, and grid, referring to the sheet and stiffeners structure.
...
The stiffeners of an isogrid are generally machined from a single sheet of material with a CNC milling machine, but a thickness less than 0.040 in. (1.0 millimeter) requires chemical milling processes.
Metal isogrids (often aluminum), are constructed by milling material from one face of a sheet or plate. Composite isogrids are rib-skin[clarification needed] configurations formed by various manual or automated processes , and can give extremely high strength-weight ratios.

Actually, 1mm aluminum is pretty thick. I heard Apollo LM had a pressure vessel just 5 times the thickness of kitchen aluminum foil. Pop cans hold pressure, and they're pretty thin. The pull-tab is pure aluminum, but the pop-can itself (pressure vessel) is an alloy.
This document provides more technical detail: apollo experience report - lunar module structural subsystem
It gives thickness of areas of the descent stage, but I don't see thickness of the pressure vessel of the ascent stage.

Apollo LM used a pressure vessel with ribs for reinforcement. Over that was a micrometeoroid protection layer. Today we would use the same thermal and micrometeoroid protection blankets as ISS.

Again, the goal is reduce mass. Keep launch mass down so a Dragon spacecraft, lunar module, and LOI/de-orbit stage can all be launched on a single SLS block 1.

SpaceNut · 2016-12-04 23:31:29

This being one of the newer topics for moon missions here is a video for Private plan to send moon rovers to Apollo 17 site Dec. 02, 2016 - 1:37 - Mission to inspect Apollo moon buggy explained on 'America's Newsroom'

This would be a positive for getting an audiance to take interest in spending some money at least for 1 mission....

elderflower · 2016-12-05 07:05:10

Has anybody any idea of the effect of a solar flare and mass ejection on a lunar power station? We have seen some of what can happen on earth, but I'm not sure how the earth's magnetic field might influence the impact and make it different to the impact on the moon.

SpaceNut · 2016-12-05 21:16:23

Ask and I will google for answers

https://en.wikipedia.org/wiki/Coronal_mass_ejection

What impact do solar flares have on human activities?

Sickening Solar Flares

http://www.space.com/11506-space-weathe … tions.html

Could be very deadly in the open on the moons surface and to power systems not well protected...

GW Johnson · 2016-12-06 12:36:23

According to what I got off NASA's own radiation website, this solar flare/CME stuff is exactly what 15-20 cm of water protects very effectively against. So, on the moon or Mars, put your water and wastewater tanks overhead. Or use a meter or so of ice-in-regolith for your roof.

GW

SpaceNut · 2016-12-06 19:13:13

Is there a way to teach me how to take a red dragon from lunar orbit land with some legs on it and then take off after a short stay? I am looking at a modified design for lunar use to serve as a taxi to a base.

GW Johnson · 2016-12-07 17:01:27

Well, you'll need a weight statement for a Red Dragon or a Dragon v2. Red Dragon is the manned Dragon with the seats and life support ripped out. Both have legs and the big Super Draco thrusters. That weight statement should have an unladen dry weight. The propellant weight is 1200 kg of MMH-NTO. Vacuum Isp ought to be in the neighborhood of 310-315 sec.

You can estimate exhaust velocity Vex = Isp * gc, where gc is the standard earth gravity constant (for units consistency). SI gc would be 9.80667 m/s^2. For US units, use 32.174 ft/sec^2. SI units will be del-Vee m/sec, and for US units, feet/sec.

Take your unladen dry weight, and add whatever you are trying to carry (men, equipment, or both). That's your burnout weight Wbo. Then add the 1200 kg propellant weight. That is your ignition weight Wig.

The theoretical delta Vee just comes from the rocket equation. Mass ratio MR = Wig/Wbo. delV = Vex ln(MR). Then knock off about 2 or 3% for gravity losses and unusable fuel allowance. Whatever that number is, that is all the capsule can do, burning from full to dry tanks. It'll be in the vicinity of 1 to 1.5 km/sec, depending on the load being carried, I think.

Whatever the delta-Vee required is from surface to orbit on the moon, your capsule delta vee must exceed that value for a one-way trip. For a two-way trip, your capsule delta-vee must exceed twice the velocity requirement surface to orbit.

GW

Last edited by GW Johnson (2016-12-07 17:02:03)

kbd512 · 2016-12-07 17:51:04

SpaceNut wrote:

Is there a way to teach me how to take a red dragon from lunar orbit land with some legs on it and then take off after a short stay? I am looking at a modified design for lunar use to serve as a taxi to a base.

SpaceNut,

A modified Dragon V2 with half its normal pressurized volume devoted to propellant and a service module loaded with propellant could potentially land and return to LLO. Additional propellant is required to get back to Earth, so the propellant for Earth return must be pre-positioned in lunar orbit. ExoLiner or some other vehicle would have to deliver it. We should maintain some sort of space station at L1 or L2 for propellant storage and deep space simulation.

SpaceNut · 2016-12-07 21:03:17

Thanks for the way to work the equations for using a space x capsule vehicle for moon or mars GW and for the follow up input for what would also be a must to have kbd512.

Did a bit more googling and located this web page which worked out the numbers in a simular fashion.
Dragon 2 Landing Calculations & Analysis for Multiple Solar System Bodies

What makes a dragon to land possible for Mars is why a lunar landing is not possible without modifications to fuel amount and stripping of unrequired mass (heat shield, extra seats for no crew members, ect... ) for moon landing barely doable.

The same reason a fully fueled up dragon on the mars surface can not return to orbit while a lunar senerio of the same can....

Its the pressence and lack of an atmosphere....

So for each a new landing stage and change of fuel allotment would be needed for both. The moon would use up all the fuel to make a landing possible for this new landing stage while mars would only use a portion of it and would be used as a first stage with the capsules draco finishing the remaining push to orbit. Both depending of mission duration would need a habitat modular and return capsule to be parked in orbit for both situations.

The mars version would need a large return stage fueled in orbit with compareable supplies to make a small mission possible. The moons would just be used for the return time back so it can be smaller but able to make a crew happy.

GW Johnson · 2016-12-08 11:29:10

Spacenut:

I went and looked at the Reddit site analysis via your link just above, and the FAA document it cites as its data source. I see some problems with those numbers, although the trends are more-or-less right.

The FAA document does not describe either Dragon, Dragon v.2, or Red Dragon. It describes a proposed test vehicle named DragonFly, illustrated as a modified cargo Dragon v.1 and trunk, with Super Draco's and steel landing legs added to the trunk. The weight shown for DragonFly is 14,000 lbm, = 6349 kg, which includes the trunk. This weight statement would definitely NOT apply "as-is" to a Dragon v.2 or to a Red Dragon. Also, v.1 and v.2 trunks are not the same.

The Isp numbers he uses did not come from the FAA document, but they are in the ballpark, because they match up within a second or two with what was published for MMH-NTO in my ancient Pratt & Whitney Vest-Pocket Handbook, as listed for those propellants. But without the right weight statement, his estimate of capsule delta-vee of only 400+ m/s is way off. It's closer to 1-1.4 km/s, I believe, depending on the carried payload. Nevertheless, even if I am right, it's still insufficient for propulsive landing on the moon, which needs pretty close to 1.7 km/s one-way from orbit.

I don't buy the "terminal velocity" thing he did, either. For one thing, his Mars surface density of .02 kg/m^3 is about factor 2 too high. It's much closer to .01 kg/m^3, and quite highly variable from place to place and time to time. He has about the right hypersonic drag coefficient, and roughly the right heat shield blockage area, though. I'm not sure I agree with his subsonic value of drag coefficient, and he completely left out of consideration the transonic drag rise, which ought to be in the vicinity of CD = 2 to 3 (about twice the hypersonic value) at Mach = 1.1-ish.

Your conclusion about presence versus absence of an atmosphere is exactly right. Coming out of hypersonics on Mars around Mach 3 somewhere between 5 and 15 km altitude (in essentially vacuum conditions) is a flight velocity in the vicinity of 0.7 km/s. If you have 1-1.4 km/s delta-vee available, you can clearly make a powered landing from that point. It is having at least 1 km/s that limits your mass ratio and thus your max carried payload weight in Red Dragon. But, don't count on being able to use all your propellant loadout: (1) there is at least around 2-3% you just cannot get out of the tanks, and (2) the Dragon's small attitude thrusters ("ordinary" Draco's) draw on the same propellant supply, and are required.

Dragon v.2/Red Dragon can land on small airless bodies where the delta vee requirement to be imposed on the capsule-without-trunk is around 0.7 km/s or less. Less delta-vee requirement is larger max payload weight capacity. Beware whether you are looking at escape or orbital velocities. The ratio of escape speed to circular orbit speed is square root of two, a factor of 1.41.

Otherwise, you will need a powered stage to replace the trunk, and you would have to land using that, which does not work with an atmosphere (no heat shield). It would extremely difficult to couple an added propellant tank set to the capsule from the trunk, and you certainly do not want propellant tanks inside the pressure cabin.

As for weight statements, what you need is the capsule-only unladen dry weight, the payload weight of people and/or cargo to be carried within it, and the propellant weight loadable into it. For the trunk, there is an unladen weight, and a cargo weight it can carry. The rocket launches capsule+trunk. What lands is capsule-without-trunk. I don't have data for these, Spacex does not list anything but Dragon v.1 payload weights on its site.

GW

Last edited by GW Johnson (2016-12-08 11:49:28)

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