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Terraformer

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Constructing a human mission, a tonne at a time

Assuming that a cheap (<$100/kg) launcher has been built that can throw 1 tonne payloads into LEO, how would you go about developing a human interplanetary mission from such payloads?

First off, I think GW Johnson's frame and fabric workshop would be a good idea. It should be possible to construct one from 1 tonne payloads, given the nature of the structure. With that, we have somewhere to work.

If we can use larger launchers, though, it would be very simple to launch a mission. The Falcon Heavy (non-reusable) will be able to put 53 tonnes into orbit. If a few launches were made, components could be docked together into a baton to form the basic hull of the ship. Fuel, provisions, and internal components could be flown up separately, allowing a large mission (300+ tonnes to Mars) to be launched.

Without that, though, we'd have to learn how to make pressure vessels on orbit. Of course, once we learn how to do that we could manufacture some very large vessels...

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RobS

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Re: Constructing a human mission, a tonne at a time

I can't wrap my heard around your assumption, Terraformer. One tonne at a time? Why?

RobertDyck

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Re: Constructing a human mission, a tonne at a time

Falcon 9 is reusable, will launch a reused first stage this fall, possibly the next launch. It can launch Dragon to ISS. Dragon can deliver 3,310 kg (7,300 lb) total payload including pressurized and non-pressurized. "Dragon Lab" can deliver 6,000kg to LEO, but that's to a lower orbit than ISS. Dragon uses the large square CBM hatch that an equipment rack can pass through. So it can deliver all internal equipment for a space station or spacecraft. Dragon itself has a dry mass of 4,200kg and total propellant mass of 1,290kg, so this means a Falcon 9 should be able to deliver a pressurized habitat to ISS with total mass = 3,310kg + 4,200kg + 1,290kg including RCS thrusters, propellant, and rendezvous systems. If the habitat is empty other than rendezvous systems, that could be a large hab. Internal equipment installed later, using ISS as construction shack.

In another thread (Their back... NASA revives the wet workshop concept) Excelsior posted an article that a NASA contractor called Ixion proposed a wet-launch concept. Using the LH2 tank of the Centaur upper stage of an Altas V rocket as a living space for ISS. Their proposal would launch a Cygnus cargo ship as normal, but instead of the Centaur upper stage being discarded, it would remain attached. A small adapter would have a CBM hatch and crapple point for the station's arm.

Before all this, several times, I posted my idea. My idea is a custom upper stage for Falcon 9 full-thrust launched expendable. The upper stage would be LH2/LOX. This would not launch any payload at all, instead the upper stage is the payload. It would have RCS thrusters and rendezvous systems for ISS. A CBM docking hatch, and grapple point for the station arm. The LH2 tank would be the deep space habitat. Launch essentially empty, but with internal walls/bulkheads, tank wall strong enough to be the pressure wall, launch with thermal blankets and micrometeoroid shield for deep-space use. Dragon uses solar arrays to power electronics for its autopilot and rendezvous systems, so give this habitat solar arrays. But make the solar arrays full size for a human mission to Mars and back. Internal equipment like beds, life support, etc would be delivered later via Dragon CRS (Cargo Resupply Ship). The LOX tank and upper stage main engine would be detached at ISS and de-orbited.

Note: If the habitat has greater than 5 metre diameter, then gimbals of the first stage will require a greater range of motion. Mars Direct habitat had 8.4 metre outside diameter, 8.0 meter inside diameter, so 0.2 meter (20 cm = 8") thick walls. That was simply to match the first stage of the Ares launch vehicle, which was based on the external tank of Shuttle. SLS is based on Ares, also will have the same diameter. If we want a hab that size, then Falcon 9 first stage engine gimbals require ±15° movement. Based on a post on another space forum.

I posted my mission architecture many times. I started assuming the Russian Energia, because Robert Zubrin himself first mentioned Energia in his book "The Case for Mars", and many others in the Mars Society gushed about Energia in 1998 & 1999. That was spoiled when relations soured after Putin. Then I reconfigured for SLS. RobS asked me to reconfigure for Falcon Heavy. We could do that, or break it up into even smaller pieces for Falcon 9. But even that is much larger than 1 tonne to LEO.

GW Johnson

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Re: Constructing a human mission, a tonne at a time

I agree with RobertDyck.  There is no need to do this 1 ton at a time.  Maybe 15-20 tons at a time.  Read on. 

We have rockets today launching 15-20 tons to LEO,  at around $2500/lb if fully loaded (lb refers to lb of delivered payload).  By next year we should have one rocket launching 53 tons to LEO (Spacex Falcon-Heavy),  at around $1000/lb if fully loaded. 

If the SLS ever really flies,  it will launch 70-130 tons to LEO.  This might be for around $3000-6000/lb if fully loaded.  Depends upon whose estimates you believe.  Cannot happen for 3-5 years yet,  even at the 70 ton level.  This is 1960's support technology operating with 1980's shuttle technology. 

If Spacex actually gets its MCT flying,  you are talking about ~100 tons to the surface of Mars,  based on refueling in LEO.  That's beaucoup tons to LEO.  No one knows how much this will cost,  although my graph extrapolates as well below $1000/lb,  if flying fully loaded.  Would you believe $300/lb?  $500/lb?  Nothing but speculation as of yet. 

Bigger rockets really are cheaper to launch,  on a basis of (1) fully loaded,  and (2) expendable.  We've seen it drop from around $10,000/lb in the 1980's to today's $2500/lb,  because of simplifying the support logistics:  using fewer people to support manufacture,  checkout,  and flight.  What effect re-using stages might have is still unknown at this time,  but can only improve things. That's why Spacex is pursuing it.   

But you do not have to have the even-bigger rockets.  We built the ISS on-orbit by docking together things of 15 tons or less.  The cost was driven by the $27,000+/lb of shuttle,  not the payload masses,  which only needed to stay under 15 tons to high-inclination LEO. 

It's already "feasible" to do lots of things with orbital assembly-by-docking at the 15+ ton size and expendable launch prices.  It'll only get better from here,  as long as we do NOT restrict ourselves to using SLS. 

GW

Last edited by GW Johnson (2016-08-28 18:05:12)

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GW Johnson
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RobertDyck

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Re: Constructing a human mission, a tonne at a time

One argument could be lower cost through mass production. But larger rockets are more efficient. Metal of the tank is surface area, which increases as the square of size, while volume increases the cube, so you have less metal per unit volume. But then additional weight of fuel (mass x acceleration) requires stronger tank walls, so it's not perfect square-cube. Cryogenic propellants boil off less with less surface area, so cryogenics work better with large rockets. But small rockets are easier to handle, don't require gigantic handling equipment like the Saturn V crawler. But Falcon 9 is already delivered by truck. With empty propellant tanks; a truck couldn't carry it if the tanks were full. Propellant is loaded on the launch pad. And the metal tracks of the crawler crush the river stones laid on the crawl-way, those stones have to be replaced every time. A truck just drives on a road, the road isn't destroyed by driving on it once.

All those arguments appear to be converging on a combination of Falcon 9 and Falcon Heavy.

Energia used a grasshopper crawler that drove on two railway tracks; that is 4 rails. With concrete ties that don't degrade. It didn't require fresh river stones every time the crawler went down. But it did require a big crawler. It was called "grasshopper" because the rocket was carried horizontal, which meant the crawler could drive at much higher speed without risk of the rocket toppling. The "grasshopper" was the erector that lifted it to vertical at the launch pad. Falcon 9 does this, as does Atlas V and Delta IV, but they're all rockets small enough to be carried by a truck with rubber tires.

Terraformer

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Re: Constructing a human mission, a tonne at a time

Wow, this went off topic quickly...

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RobertDyck

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Re: Constructing a human mission, a tonne at a time

Wow, this went off topic quickly...

No, it didn't. I listed available launchers, cost, and practical limits of size of chunks to construct a human mission. If you want to construct a human mission with small pieces launched at a time, your assumption of "one tonne" is wrong.

GW Johnson

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Re: Constructing a human mission, a tonne at a time

Well,  the "one ton" is only in the thread title.  The real point here is that there really is a sort-of-optimal "chunk" size for constructing things in LEO.  These years it's around 15-20 tons. 

In the near future (next 20 years),  it may be a little larger,  around 50 tons,  once Falcon-heavy starts flying regularly,  and there are more like it.  Not until there are more like it,  though. 

I rather doubt the SLS will reset that trend to the 100-ton range,  because current estimates say it is just too expensive to use except at great compelling need for the larger "chunk" size. 

There is light gas gun technology to develop and try out.  This may be an even cheaper way to launch bulk propellants for refueling in LEO,  as long as the containers are very gee-hardened (launches are ~1000 gee,  typically).  Proponents of the concept point to estimates as low as $50/lb to LEO.  Won't be operational anytime soon,  but maybe around 20 years from now,  if we start now. 

GW

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Antius

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Re: Constructing a human mission, a tonne at a time

Falcon 9 is reusable, will launch a reused first stage this fall, possibly the next launch. It can launch Dragon to ISS. Dragon can deliver 3,310 kg (7,300 lb) total payload including pressurized and non-pressurized. "Dragon Lab" can deliver 6,000kg to LEO, but that's to a lower orbit than ISS. Dragon uses the large square CBM hatch that an equipment rack can pass through. So it can deliver all internal equipment for a space station or spacecraft. Dragon itself has a dry mass of 4,200kg and total propellant mass of 1,290kg, so this means a Falcon 9 should be able to deliver a pressurized habitat to ISS with total mass = 3,310kg + 4,200kg + 1,290kg including RCS thrusters, propellant, and rendezvous systems. If the habitat is empty other than rendezvous systems, that could be a large hab. Internal equipment installed later, using ISS as construction shack.

In another thread (Their back... NASA revives the wet workshop concept) Excelsior posted an article that a NASA contractor called Ixion proposed a wet-launch concept. Using the LH2 tank of the Centaur upper stage of an Altas V rocket as a living space for ISS. Their proposal would launch a Cygnus cargo ship as normal, but instead of the Centaur upper stage being discarded, it would remain attached. A small adapter would have a CBM hatch and crapple point for the station's arm.

Before all this, several times, I posted my idea. My idea is a custom upper stage for Falcon 9 full-thrust launched expendable. The upper stage would be LH2/LOX. This would not launch any payload at all, instead the upper stage is the payload. It would have RCS thrusters and rendezvous systems for ISS. A CBM docking hatch, and grapple point for the station arm. The LH2 tank would be the deep space habitat. Launch essentially empty, but with internal walls/bulkheads, tank wall strong enough to be the pressure wall, launch with thermal blankets and micrometeoroid shield for deep-space use. Dragon uses solar arrays to power electronics for its autopilot and rendezvous systems, so give this habitat solar arrays. But make the solar arrays full size for a human mission to Mars and back. Internal equipment like beds, life support, etc would be delivered later via Dragon CRS (Cargo Resupply Ship). The LOX tank and upper stage main engine would be detached at ISS and de-orbited.

Note: If the habitat has greater than 5 metre diameter, then gimbals of the first stage will require a greater range of motion. Mars Direct habitat had 8.4 metre outside diameter, 8.0 meter inside diameter, so 0.2 meter (20 cm = 8") thick walls. That was simply to match the first stage of the Ares launch vehicle, which was based on the external tank of Shuttle. SLS is based on Ares, also will have the same diameter. If we want a hab that size, then Falcon 9 first stage engine gimbals require ±15° movement. Based on a post on another space forum.

I posted my mission architecture many times. I started assuming the Russian Energia, because Robert Zubrin himself first mentioned Energia in his book "The Case for Mars", and many others in the Mars Society gushed about Energia in 1998 & 1999. That was spoiled when relations soured after Putin. Then I reconfigured for SLS. RobS asked me to reconfigure for Falcon Heavy. We could do that, or break it up into even smaller pieces for Falcon 9. But even that is much larger than 1 tonne to LEO.

Apologies for not chipping in with something more constructive earlier on.  I am a safety engineer with some nuclear/mechanical background, with scraps of time to devote to those things that I find really interesting, such as colonisation of other planets.  So, I will try to contribute something useful with what little time and expertise I have to offer.

I have often thought that this was a good idea, though could not have articulated it so well.  Reusability for a space launch vehicle could be achieved by either returning it to Earth and using it in the same way again (which wastes the fuel needed to launch it to orbit in the first place) or designing it in such a way that it can be used for something else when it reaches orbit.  The second option seems much more sensible, but entails some difficulty designing a module that will tolerate being immersed in propellant.

A few initial thoughts come to mind: (1) Propellant tanks have a design pressure of several bars for pump fed engines, so the tanks are over engineered as human rated modules, which have design pressure of 1 bar or less; (2) Cryogenic tanks are equipped with insulation that would be redundant for a human habitat; (3) Propellants tend to saturate many materials.  A butane tank will require some weeks of exposure to atmosphere at 1 bar before the stench of butane diminishes; (4) The contents of the module must be compatible with the propellant being stored; (5) Not all parts of a vehicle need to be reused in the same way, I will elaborate in the following sections.

It is interesting to note that in theory at least, chamber pressure becomes irrelevant to efficiency when a rocket engine fires in a vacuum.  Maybe we can design an upper stage in which the design requirements of a propellant tank and habitation space align, such that the tank can be readily reused as a space station module or Mars transfer vehicle hab pressure vessel.  Most of the mass of a redundant stage is in its empty propellant tanks.  Most of the engineering complexity that we want to recycle is in the form of engine, propellant pumps, guidance system and manoeuvring thrusters.  Hence, the optimum reusable upper stage would be the one that discards the propellant tanks in orbit, where they can be used for something else, and returns the complex vitamin parts to Earth.  Hence, we need an upper stage in which the engine, guidance and manoeuvring components are housed in a compact cone shaped reentry vehicle, with detachable propellant tanks that are discarded or reused in orbit.  That way, we reuse the complex parts, which are most useful if they are reused in the same mode, and recycle the simple but massive parts, the propellant tanks.  These carry a lot of potential energy, but are not valuable enough in terms of embedded human labour to justify protecting them with their own heat shield and reusing them in the same mode.

Building an upper stage in this way is easier if the aerodynamic shell of the launch vehicle is part of the first (lower) stage.  That way, the geometry and aerodynamics of the upper stage are unimportant, as it is only deployed in vacuum.  Depending upon the propellant used, it may require minimal insulation, such that propellant tanks are basically space station modules full of propellant.  The first stage on the ground, would carry the upper stage internally and would deploy it at 100,000'> through bay doors rather like those on the space shuttle.  The lower stage would fly straight up, and would contribute perhaps 2km/s to the total delta-V before releasing the upper stage, deploying its drag-chute and returning to Earth.  The upper stage itself would consist of engine, guidance and manoeuvring componants, which would be integrated into a single compact cone shaped reentry vehicle; propellant tanks, which may be fitted out as modules; and payload at the front, requiring little or no housing.

I think the idea of building missions from one-tonne payloads came from an earlier thread, in which we speculated that launching dozens of small payloads using reusable two-stage launchers and assembling in orbit, might be cheaper than a single heavy lift.  The reasons had to do with economy of scale and manufacturability of smaller propellant tanks and combustion chambers, using cold flow-forming techniques.  These techniques cannot produce tanks 24"> in diameter and are therefore better suited to smaller launch vehicles.

Last edited by Antius (2016-08-29 16:49:28)

Terraformer

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Re: Constructing a human mission, a tonne at a time

Anyway, back on topic... what can we do with 1 tonne chunks? I've already mentioned the construction shack idea. Could we assemble large probes, fuel them up, and send them on their way? What about launching small supply depots to litter the surface of Mars, filled up in LEO with supplies and then launched?

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SpaceNut

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Re: Constructing a human mission, a tonne at a time

The topic of "Constructing a human mission, a tonne at a time" is it to assume that this starts after launch with given number of crew and if so then its the amount of time that life support can sustain them until you reach the measurement of the first tonne....So after the numbers are implemented for food, water, air, waste recovery of water, processing of co2, processing of other solid waste...finally with the sizing of the power source to keep these things all running, lighting, heat, air conditioning, air recycling... to which the numbers just keep climbing as the insidentals are all put into the equation the first tonne is filled in pretty quickly and we are not even out of orbit yet.......Ah forgot to account for the holding containers for each of these items as well.......

Antius

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Re: Constructing a human mission, a tonne at a time

Anyway, back on topic... what can we do with 1 tonne chunks? I've already mentioned the construction shack idea. Could we assemble large probes, fuel them up, and send them on their way? What about launching small supply depots to litter the surface of Mars, filled up in LEO with supplies and then launched?

The low-density of the Martian atmosphere limits the size of vehicles that can be practically landed by parachute on its surface.  The 1-tonne per launch idea would allow us to integrate individual payloads into a larger bus in Earth orbit.  Instead of opting for a Mars-direct multiple independent mission idea, we could choose a location for a central base, deliver its components a few hundred kg at a time over a period of several years and then send a minimum mass manned mission to assemble those components into a base.  All subsequent human missions land at the base, rather than fresh sites.  This reduces the design requirements of human missions, which can utilise the installed assets of the Martian surface and can therefore be more focused upon maintaining the crew on the outbound and return trips.

Exploration of the planet then proceeds from a single site using ground based assets, rather than mounting fresh missions from Earth with entirely new assets.  We would send a single hab to Mars (in pieces) and the crew would travel to Mars in an ERV, which would be optimised for that purpose alone and hence would be lighter.

Last edited by Antius (2016-08-29 17:13:37)

RobertDyck

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Re: Constructing a human mission, a tonne at a time

As mentioned in Robert Zubrin's book "The Case for Mars", a contractor for NASA was already working on a fabric heat shield that could unfold like an umbrella. That allows landing a heavier payload with heat shield and parachute. I discovered the NASA project working on this is called ADEPT. They worked out launch mass for a given payload for various configurations, including supersonic retro-propulsion. It was still most efficient to use heat shield and parachute, rockets just for terminal descent and landing. Landing like the Viking landers or Phoenix. There is a limit to payload size, but they calculated for 40 metric tonne payload, which is larger than the Mars Direct habitat.

SpaceNut

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Re: Constructing a human mission, a tonne at a time

Landed payload accounts for both the mass of the shell, engines tanks for the lander and cuts into the amont of mass that is actually the payload landed on the surface.  So what would the lander mass account for in this design so that we would know how much payload we can actually expect to have to make use of on the surface.

RobertDyck

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Re: Constructing a human mission, a tonne at a time

I got the chart from this PowerPoint, taken from a NASA website:
http://www.lpi.usra.edu/vexag/Nov2012/p … cinski.pdf

DACC Project GAME CHANGING DEVELOPMENT Enabling Venus In-Situ Science – Deployable Entry System Technology, Adaptive Deployable Entry and Placement Technology (ADEPT): A Technology Development Project funded by Game Changing Development Program of the Space Technology Program

Mars application is on page 6. It doesn't break down landed payload further. However one difference from Mars Direct is landing legs. These guys obsess over their own technology. They propose "popping" the ribs like an umbrella caught in the wind, using those ribs as landing legs. Mars Direct included legs with shock absorbers like the Apollo LM.

I could post mass break-down from various versions of Mars Direct. Robert Zubrin has done it a few times, each a little different.

RobertDyck

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Re: Constructing a human mission, a tonne at a time

Here is the Mars Direct habitat from Robert Zubrin's first presentation 1990.

Notice this version has a single floor/deck only. Below the living space is solid equipment, including life support, landing engines and propellant tanks. This is how Apollo was built: Command Module and Service Module, with SM not accessible in space. Presumably the rover would be slung underneath, nestled between landing engines. The rover could be lowered with a winch. That would expose the rover to rocks thrown up by rocket exhaust during landing; later versions include a "garage" to house/protect the rover during landing. Also experience on ISS demonstrates astronauts need access to life support equipment. When operated over many months, it requires frequent maintenance/repairs. However, a real Mars Direct habitat would not have a full lower floor/deck like FMARS or MDRS. The lower deck would have an airlock, storage compartment the size of a single car garage for the rover, surface science equipment, and inflatable greenhouse. The rest would be solid equipment. Life support would be housed in pressurized compartments just large enough for an equipment rack, with door opening into the garage. Think of one wall of the garage being nothing but access doors into life support. No room for anyone to craw into that. Think of a door that opens to a furnace, the furnace is just inches from the door so opening the door gives you access to the furnace but nothing else. It would have to be sealed so that life support remains pressurized when the garage is depressurized for rover egress. Life support on the US side of ISS is 3 full size equipment racks, plus regenerable CO2 sorbent that's roughly the size of another rack, plus batteries to store power over night from solar panels. Those batteries would most probably be lithium iron phosphate, the latest lithium ion batteries that can withstand colder temperatures. So that's a total of 5 equipment racks. The lower deck will also require landing rockets, most likely around the periphery like the skycrane of Curiosity rather than a single central engine like the Apollo LM. And propellant tanks for the terminal descent and landing rockets. And RCS thrusters for manoeuvring in space, plus propellant tanks for those. Plus the mechanism for the landing legs.

Note: The aeroshell is discarded before landing. The back shell is discarded before parachute deployment, and heat shield is discarded before terminal descent rockets fire. The ADEPT team suggested using umbrella ribs for landing legs, but that means it would have to discard the fabric to allow terminal descent rocket exhaust to get out. How do you ensure the fabric doesn't come free during hypersonic atmospheric entry, yet discard the fabric for terminal descent? I think it would be easier to discard the entire heat shield, and use separate landing legs.

An image from the movie "Mission to Mars". This is obviously based on Mars Direct.

RobertDyck

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Re: Constructing a human mission, a tonne at a time

This was my attempt to answer the question by SpaceNut. The aeroshell is not part of landed payload mass. The pressure shell of the habitat is. The slide provides mass for the pressure shell, and internal walls and decks. However, it doesn't include landing engines, propellant tanks, or legs. An early presentation included a separate section for landing rockets, propellant tanks, and heat shield. That was common for the hab and ERV. I read somewhere that part was designed by David Baker. Can't find mass for that now, but here's an image. Images of the hab appear to indicate landing legs were the vertical support struts of the heat shield structure. So it wasn't the ribs as the ADEPT team would suggest, but David Baker modified the concept so the landing legs were integrated with the structure of the deployable heat shield in a way that works.

MDRS appears to have vertical legs that fold out for landing. It appears to be an attempt to simulate this.

RobertDyck

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Re: Constructing a human mission, a tonne at a time

So back to the topic. The "Main Structure" in the slide for Mars Direct is 6.72 metric tonnes. I have the 1997 edition of "The Case for Mars", it has a two deck habitat so structure mass is a little different. I could post that, but the pressure shell of the habitat is a few tonnes. How do you assemble something like that with a launcher that delivers only 1 tonne at a time to LEO?

Void

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Re: Constructing a human mission, a tonne at a time

I typically do not post to this section, but I felt like it this time.

Terraformer opened up the topic with:

Anyway, back on topic... what can we do with 1 tonne chunks? I've already mentioned the construction shack idea. Could we assemble large probes, fuel them up, and send them on their way? What about launching small supply depots to litter the surface of Mars, filled up in LEO with supplies and then launched?

I do not intend to interfere with what RobertDyck has posted for the "Main" mission, Mars Direct.

I have noted that GW has indicated that efficiency/cost effectiveness is important.  I believe that has to do with dealing with the atmospheric friction load to a large extent, many small loads = more composite atmospheric friction to loft the total payload.  And then there is the need to deal with what hardware really exists and is available.

So, I will regard the 1 Ton idea as a guideline rather than a mandate.

Apparently costs are related to recycling machinery.  That is why SpaceX and others are trying to recycle their first stages.  They are working on it, and it looks like they might do it.

As for the second stages, it appears that that is much more close to wishes than possibility.

Terraformers instructions per 1 ton and assembly in space appear to me to veer towards mass production assembly line activities, and that is a good notion.  Originally, missions have tended towards one of a kind, or a set of a kind.

I am going to suggest a reusable tug to assist in Terraformers "What about launching small supply depots to litter the surface of Mars".  (Which is sort of a subpart of what he communicated).

What I have in mind is a container which will be unpersoned, and will involve two propulsion systems, one chemical, and one electric.  It would also use lunar gravity to do a free return to lower Earth orbit for itself, but not for it's payload.  It's payload would use a gravity assist to go to Mars.  Since the tug would need electrical power of significance to use it's electric rocket, it would require solar panels, I feel.

...

So, now I will attempt to describe a "Cycle" of this presumably re-usable "Tug".
1) Of course it has to originally be put into LEO, and would be mated to a service/space station, that station having humans in it.
*An airlock would encompass all the significant engine nozzles, except perhaps maneuvering thrusters.  (Best if it encompassed all thrusters).
*A pressurized habitat module would allow the extraction of many of the "Modular" guts of the machine into it, for minor servicing.
2) The "Tug" being fully assembled would be fueled for both type of propulsion, and set loose when appropriate.  A cargo bundle would be attached to the opposite end from the airlock, when it is most suitable.
3) Although I suppose you could have such a tug with electric propulsion only, time is money, so, instead of fooling around, you would send the package to interact with the moon for two different slingshots.  The payload to continue towards Mars, and the "Tug" to swing around for a free return towards Earth.  Unlike Apollo, you would not want the Perigee to bring it in too close, deep into the atmosphere.  So, I suppose you would start towards the Moon with a chemical burn.
4) If you have managed to put it into an elliptical orbit, then using the Moon (And chemical thrusters if needed), this robot can use two interacting methods to circularize it's orbit.  The electric rocket, and if desired perhaps the art of grazing the top of the atmosphere could be used also.  I presume "Practice Makes Perfect" for this.  If you do it a lot, eventually you will build robots that usually don't screw up.
5) Once the "Tugs" orbit is circular, it mates up again with the Servicing/Space Station in LEO.  (Proper purging required).
6) It is maintained to return to it's next call to service.
*As part of the maintenance, if "Modular Chunks" require more serious servicing, they are extracted and if of a suitable size can be brought to the Earths surface of Corporate spacecraft.  (Or just replaced).

...
As for the payload headed for Mars, I suggest that the Hohmann transfer method be avoided , instead use the "Ballistic" method when desired, to attain Martian orbit.
http://www.scientificamerican.com/artic … the-cheap/

This brute force approach to attaining orbit, called a Hohmann transfer, has served historically deep-pocketed space agencies well enough. But in an era of shrinking science budgets the Hohmann transfer's price tag and inherent riskiness look limiting.

Now new research lays out a smoother, safer way to achieve Martian orbit without being restricted by launch windows or busting the bank. Called ballistic capture, it could help open the Martian frontier for more robotic missions, future manned expeditions and even colonization efforts. "It's an eye-opener," says James Green, director of NASA's Planetary Science Division. "It could be a pretty big step for us and really save us resources and capability, which is always what we're looking for."

The premise of a ballistic capture: Instead of shooting for the location Mars will be in its orbit where the spacecraft will meet it, as is conventionally done with Hohmann transfers, a spacecraft is casually lobbed into a Mars-like orbit so that it flies ahead of the planet. Although launch and cruise costs remain the same, the big burn to slow down and hit the Martian bull's-eye—as in the Hohmann scenario—is done away with. For ballistic capture, the spacecraft cruises a bit slower than Mars itself as the planet runs its orbital lap around the sun. Mars eventually creeps up on the spacecraft, gravitationally snagging it into a planetary orbit. "That's the magic of ballistic capture—it's like flying in formation," says Edward Belbruno, a visiting associated researcher at Princeton University and co-author, with Francesco Topputo of the Polytechnic University of Milan, of a paper detailing the new path to Mars and the physics behind it. The paper, posted on arXiv, has been submitted to the journal Celestial Mechanics and Dynamical Astronomy.

If I understand how "Ballistic Capture" works:
-The payload is in an elliptical orbit.
-Timing puts it in a apogee just in front of Mars.
-The payload is traveling at a slower speed that Mars, because it is at the "Top" of it's orbit, and it is not in a more circular orbit like Mars.
-Mars catches up with it (If your timing and location are right).
-The payload "Falls" into the gravity well of Mars from and is no longer dominated by the suns gravity well.
*So Mars gives it a gravity assist to more circularize the payloads orbit.  Since these are to be unpersoned parcels, an extra few months travel time shouldn't matter, for the case of pre-positioning supplies and equipment for a main mission.  Re-supply could be more of an issue, if you had a potentially mishap on Mars, after the crew arrived,  if you did not plan for mishaps, however, and needed to get supplies there fast, then a Hohmann capability should be retained to cut the re-supply time.  It would cost more, and your payload would be smaller, but it would be faster.

So, anyway, I think that it will be more possible to recycle the "Tug" than upper stages of SpaceX launchers. 

And recycling hardware is supposed to be one of the big areas to save costs.  Fuel is less so, usually.

Done.  Time to poodle jump.

Last edited by Void (2016-08-30 16:27:49)

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Done.

SpaceNut

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Re: Constructing a human mission, a tonne at a time

Thanks RobertDyck for what you have brought to the table on the design of a lander. Since the age of the design is Apollo era one could use the engines/fuel combinations from the LM and scale based on its Mars descent times. From the drawing I can see 4 engines which helps for the period of time that we have to slow the vehicle, so what we need is the firing time and comsumption rate of the fuel to work it backwards to the tank size that would be needed of course with margin to allow for error.

GW Johnson

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Registered: 2011-12-04

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Re: Constructing a human mission, a tonne at a time

If you think reusable lander then you don't need separate hab and ascent vehicles.  Why limit yourself to a non-reusable lander design?  That's thinking like Apollo flag-and-footprints,  usually.

The rocket equation clearly shows reusable one-stage designs are feasible,  even with hydrazine/NTO storables,  if you base out of low Mars orbit instead of direct entry and return. 

They're big,  because available payload fractions are low.  So what?  Retropropulsion is not mass-limited the way chutes are. 

GW

Last edited by GW Johnson (2016-08-30 18:10:39)

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GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 28,825

Re: Constructing a human mission, a tonne at a time

When considering a small 1-2 mT at a time with Dragon vehicles the reuse is not needed but only in the return to orbit MAV or ascent vehicle. All the others are reused on the surface for expansion and make it possible to not ship more habs and other such items. Just the resupply supplies for crew survival and expanded science missions.
Making the landers 1 use for reentry actually would free up mass alications to bring to the surface as more cargo.

SpaceNut

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From: New Hampshire

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Posts: 28,825

Re: Constructing a human mission, a tonne at a time

At the time we started this topic we were looking at a Red Dragon mission and with the latest Super Draco its not any more possible than landing on the moon as GW gave the quick fix to the issue which cause the ship to blow up...

kbd512

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Registered: 2015-01-02

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Re: Constructing a human mission, a tonne at a time

SpaceNut,

Lots of other hypergolic thrusters have been used for multiple firings.  The Space Shuttle's OMS system was used multiple times per mission.  They use double-valve designs to prevent the propellants from leaking.  Super Draco just has some design issues to work out.  It's not a show stopper.

SpaceNut

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From: New Hampshire

Registered: 2004-07-22

Posts: 28,825

Re: Constructing a human mission, a tonne at a time

Our current mission delivery capability to mars surface but how can we move forward with such a little mass?