New Mars Forums

European maiden flights (as have many others) have a history of failures. Both Ariane V G and Ariane V ECA failed. What they do have is a history of following successful flights when the bugs were fixed. But since they have spent all that time testing it, let us assume it will be ok. If it explodes, they find out what went wrong, fix it, try again until they have a working ATV. They plan to send one every 18 months or so. After that basic model is running, developers could start testing on an improved version. When it would be ready it would replace the basic version the same way that the ECA replaced G on Ariane 5.

ESA has an obligation to build and send ATVs as a way to pay for the running costs. Its manned program is very limited, but those ATVs are going to be built (100 million $) and launched on an Ariane 5 (150 million $) either way. It has all those autonomous capabilities, yet it uses them only once. After 6 months stay it gets dumped to make room at the port.

The ATV weighs 20 MT, but its actual cargo upload capacity is only 7,5 MT. The rest of it is a propellant and ATV dry mass. ATV can transfer its propellant to ISS, so it could also transfer propellant into ATV (technology is there). ATV is capable of multiple firings of its thrusters and could even redock multiple times.

There was a discussion about problems with space assembly. To do this you have to have a lot of “smarts” on a vehicle to bring them together. Or, at the very least you would have to have one active vehicle that would do the hard work and one passive vehicle that would have to have docking collar and some thrusters to prevent it from tumbling. Maybe the spin stabilized passive vehicle would be enough. You could launch 20 MT water tank/propellant tank/canister full of food/space module with only passive docking collar and basic stabilization thrusters into 200 km LEO. That would be the passive target to which the ATV would have to dock on one end, transfer now the combined weight to higher orbit, meet with ISS and dock on the other end with it.

That canister could be sent on any possible vehicle that can put payloads into LEO. Ariane, Soyuz, Proton, Ares, Delta, Atlas, Falcon,.. It would not matter what kind of shape it is or what is inside of it as long as ATV could dock to it (ISS inclination). Those canisters would be perfect for testing new and untested (cheap) vehicles. Canned food or water or such things are cheap. Pack them full, send them to LEO. If the rocket explodes or the canister is not placed into LEO, then no big deal. If it does deliver it, then the ATV picks it up and delivers it with “multiple redundant and extensively tested ISS collision proof” electronics to ISS.  If it would contain propellants for ATV/ISS, then the ATV could refuel itself like it refuels Zvezda module. It could contain water/gasses, which it could pump to ISS when it docks again. It could be even new module for ISS which ATV could deliver close enough to ISS so that it’s arm could grab it and position it wherever it would be placed. It could be Streached ATV’s habitation module, filled with 20 MT of supplies (reachable through port). That would be filled with waste like it is currently planed with ATV. Only that the only thing that would burn up would be the actual waste (and canister), while the ATV itself could return to ISS.

If there would be any problems with ATV, then it would be allowed to burn up and some other would be sent from ISS to do it’s job. Since ATV’s could dock at any Russian port used by Soyuz/Progress there could be lots of them. The Soyuz/Progress would now dock to ATV and the crew could reach ISS through the ATV itself.

Why would Russia not want this?

It does nothing about actual number of Soyuz manned flights. It reduces the need for a bunch of Progresses. The costs of running the ISS would fall (more delivered to ISS for less money). More people could actually live on the ISS, since there would be more then enough supplies to support them. That would mean that the Russians could build more Soyuz TMA instead of Progress, which means more paying customers.

Not to mention that the actual space on ISS would increase since every ATV has a 48 m2 pressurized section. ESA could concentrate on payload deliveries with improved ATV + canisters, Russians could concentrate on manned flights. ESA is even adopting Soyuz as it’s “medium” LV to be launched from French Guyana and could easily launch manned missions from there. It would not have to develop it’s own manned Earth to LEO transport or have its Ariane 5 “man rated”.

Win-win. 

ATV is designed to be there for six months. In that time it acts as “just another part of ISS” and has to have everything needed to survive micrometeorites, temperature changes and be as safe as any other structure.

Yes, it would have to be “hardened”, but if it can survive for 6 months it is pretty much already hardened. Add extra insulation, longer lasting electronics, stress test everything a little bit more and you are set. Cheap, mass produced space modules/tugs. All you then need is enough docking ports and even that is not a problem, since the ATV could dock to the back of another ATV.

Since they would have to be built and launched into space anyway, building them a little stronger would add minimally to the price, but it would improve ESA’s capabilities immensely. And most of those changes could be done gradually and could be tested before being actually used on newer ATVs built. Simple and free test would be to undock ATV that is planed for burn up from ISS and try to catch a Progress that would be also planed for a burn up.

As an added bonus: ATV could house experiments that could be too dangerous to be run on ISS in “a free flying laboratory and if anything goes bad it will burn in the Earth atmosphere” mode.

OK, it is the future. We have been on Mars. We have few SEPs in various orbits flying around, moving things slowly but surely. But the cost of all those rockets that must send bulky (and full) hydrogen tanks to LEO is starting to get a little high. We look around for nice big floating rocks in the range of 10-100 m, that are probably extinct comets (we can check them before with unmanned small probes like DS1). There are literally millions (http://spaceguard.esa.int/NScience/neo/ … number.htm) of them and some have delta-v from HEEO in the range of 1-3 km/s (http://neo.jpl.nasa.gov/ca/). We can use one Manned SEP that has returned back to HEEO. To it we attach all those (now empty) tanks that we had to use to bring hydrogen from Earth. We have 250 m long truss onto which we can attach them. Next, we also bring “asteroid lander” from Earth which we redock to our Manned SEP. Preferably more than one (they don’t have to be that big). Our “Mission to get Propelant” is ready to begin. The crew arrives from Earth, boards the ship, SEP fires it’s thrusters and after few months it arrives near one rock and orbit’s it in a nice distance to be safe and not have it’s wings polluted by the mining activities. The crew is completely safe and can remotely operate those “asteroid landers”. Our solar wings could even provide shade to prevent explosions of suddenly expanded gases/water.

Mining in 0 g would be like grabbing stones in water. No Asteroid is completely smooth. Most of them are rubble piles that are are loosely held together. Open your scoop (http://www.lifting-world.co.uk/Drapak%2 … 202%20.jpg), fire your thruster (10 m/s) to “land” on the asteroid. Close the scoop. If the material is loose you will get only small amounts of pebbles and dust in them. That's ok. Repeat this lot's of times and you have lots of dirt and pebbles that can be delivered to SEP for processing.

But, you can specifically try to “land” on top of a boulder that can fit inside the scoop. You either grab onto it (it is mechanically strong enough that it doesn’t brake off) or you get one rock inside the scoop. When you get the rock (or pebbles) inside the scoop, you fire your thrusters (20 m/s), return to SEP, transfer material via “elevator” (that can move from 0g to 1g on the truss) to 1 g area.

What if your grabbed rock is not a loose material? Well. You are in affect attached to the surface. You can drill/dig against it now. If your supporting rock breaks of, then it’s no big deal. Transfer it to SEP, return empty back to asteroid to repeat everything. And if you don’t break off, then you can drill and dig for as long as you want.

Your “space mining problem” is now reduced to: “Here is a (1 g) room full of dirt and ice. What can you do with it with 20 MW of electricity?”.

To get 100 MT of H2 you would need 900 MT of water. How to get water from ice is a known problem (add heat). Apply electricity, split water into H2 and 02, liquefy. Electrolysis of the water is simple (remember those 20 MW of electricity?). You can do it at your home if you wanted. Liquefaction is harder. But, luckily, what do you know: We already have liquefaction equipment onboard for our propulsion H2.  Fill our empty tanks with Hydrogen, Oxygen. You can keep the dirt and deliver it to HEEO or simply dump it (or use it for propulsion if you can). Or even better: Simply fill the tanks with water. Split what you need to return to HEEO (http://www.permanent.com/t-theory.htm), the rest would be easily stored for as long as you wanted.

After one year, you return to HEEO with enough water to supply enough Hydrogen and Oxygen for space transportation. When you spend it just go to another asteroid and do the same thing. Or you can go to Mars moons Phobos and Deimos and to that.

In my SEP tug I used MPD with Hydrogen. MPD can use various propellants. To date they have used Xenon, Argon, Neon, Hydrazine, Lithium, Hydrogen,... It’s not really picky about what you use. Isp would be in 1000-10000. And that would be good enough. And if MPD would not last long enough, there are number of other plasma thrusters that are even longer lasting and can use anything for propellant (including oxygen)..

Cost of the mission (that is not already payed for): 1 crew exchange, few small remotely operated "asteroid landers", propelant to get in orbit around asteroid (200 MT Hydrogen), Machineries to crush/melt/electrolyze dirt and water (100 MT).

Benefit: Billions in saved costs for building rockets on earth to deliver Hydrogen into LEO.

Oh, don't worry. You all make sure I get knocked the ground with questioning every little detail and pointing out the problems. Even some that are clearly solvable only hard. And, that’s good. That forces me to look at how to improve things.

If the limited world supply rules out Xenon, then our SEP would have to use something else. Ok, let us look at the baseline ship in the second link again. It’s NEP, it has 10 MW, 5000 s isp Hydrogen MDP engines. It flies on some weird Mission to Mars orbit and it’s moons, but since it delivers Crew return vehicle and habitat from LEO to Mars orbit and back with artificial gravity it’s a good starting point for a SEP long duration spacecraft. What makes up our 551 MT NEP:

- 91 MT nuclear power plant (110 W/kg)
- 32 MT Propulsion system,
- 65 MT Tanks and propellant management
- 83 MT Structures, Avionics, Habitat and Crew return vehicle
- 280 MT Hydrogen (+ 100% to the dry mass at 5000 s isp).
= 551 MT to LEO

How can we improve it? Ok, first of all, MDP engines with Hydrogen can run with isp as high as 10.000 s. Since the thrust produced with electric engines run at around 30-50 mN/KW, that means that we must get twice the power for the same thrust. That means we now have 20 MW requirement (or simply take more time to thrust with the same power). Let us replace nuclear power plant with solar cells at 500 W/kg (http://www.entechsolar.com/SPRAT05a.pdf). That means two 100 x 250 m long wings attached to the central truss. At one end of this truss we put Transhab. Around it we put smaller multilayered insulated hydrogen tanks. At the end of the truss we have one set of movable thrusters. To the other end of this 250 m long truss we put another set of movable thrusters, power converters, avionics, propellant management and bigger multilayered insulated hydrogen tanks. How does our SEP looks like now:

- 40 MT solar power plant (500 W/kg)
- 64 MT propulsion system
- 65 MT Tanks and propellant management
- 83 MT Structures, Avionics, Habitat and Crew return vehicle
- 150 MT Hydrogen (+ 60% to the dry mass at 10000 s isp?).
= 402 MT to LEO

(Out of the thin air estimate. Can anyone provide more accurate estimate?)

To carry things needed to land on Mars and actual Mars landers, you replace Habitat and Crew return vehicle with bigger tanks to get Cargo version. Cargo SEP then either delivers landers to a aerobreaked direct landing (4 km/s delta-v) or into Mars orbit (5-6 km/s delta-v). After that SEP returns to HEEO or LEO.

The landers themselves would be “just another cargo to be delivered to Mars”. If they stay on Mars (reusable) or they must be delivered new everytime (thrown away) is not important as far as SEP tug is concerned. Reusable would be preferable of course, but that depends on the money.

402 MT Crew SEP would require 10 40 MT launches. (or 3 130 MT launchers). But i think this weight is probably way too pesimistic. My guess is that the 200-300 MT/10 MW/10K s isp, would be more realistic. That would put them in the 5-7 range. Still hard, but managable.

If they are so cheap, then why is projected cost for Ares V+I 35 billion $ to develop + few billion $/year to run?

But it’s not all in the cost of rockets. SEP would be much more expensive to develop and build, but once operational it will provide reusable but more importantly safer means of transportation then the chemical/NTP. The crew will get gravity to enable really long stays (prevents bone and muscle loss) with shielding by the Transhab wall + inner multilayer tank wall + lots of Liquid Hydrogen (excellent radiation shield) + outer multilayer tank wall. That’s a lot of shielding against even the worst solar flairs (or even against Van Allen radiation).

If extra radiation protection would weigh to much, then you can simply replace them. Or you can make special version of the wings for LEO to HEEO (or L2 if you prefer) and back to LEO Sep tug with extra radiation protection. SEPs only really have to make the trip through Van Allen belt once. After that they can stay in HEEO which is much more benign.

One solution would be to make some complicated multi rotating ship or.. you can spin the whole ship and point it toward the sun. At the both ends of the truss you put one set of thrusters that would gimbal so they would always point to the same point. Since they would be at the opposite ends of the whole mass the effects would be the same as the one thruster at the center. The only time this would not work would be when the vector would point 90 degrees to the sun. Then one thruster would work for half rotation, wait until thruster can once again be pointed to the right way (during which the other thrusts) and start again. The solar cells would have to be strong enough not to brake of in 1 g. That’s like hanging them from a ceiling on earth (actually half of it, since in space only the outermost part of the cells would have 1 g. Closer to the center less force you would have).

To allow boarding and 0 g connections, we could use one “elevator” that would move along the truss to the center of rotation. You could even have one part of the truss heavier than the other (to keep hydrogen around transhab for as long as possible for example) and it would not matter.  The tanks on the “nonliving” part of the truss could work just the same in 0.3 g or 3 g (if designed that way of course). When you would want to get the crew into Mars lander, they would enter small elevator that would attach directly to transhab. Elevator would “climb” along the truss to the center, where the lander could dock to it. The elevator could even go to the other end for repairs or supplies. Or, you could fire your thrusters to stop the spin and dock to transhab directly in 0 g.

What is so “nonsense” about asteroid mining?

- get SEP from HEEO into orbit around one asteroid. Since it can do 6 – 10 km/s there are a lot of possible destinations.
- detach one (unmanned?) “Asteroid lander” that grabs pebbles from the surface and returns to SEP (100 m/s)
- process pebbles with 20 MWe in 0 – 1g environment on SEP. (melt them? what can you do on earth with "dirt"?)
- return to HEEO

or

- get SEP from HEEO into orbit around one extinct comet core
- detach one “Asteroid lander”. Grab (= dig?) the pebbles until it gets secure grip
- drill into dirt
- melt ice, pump it to lander, detach from extinct comet core, dock to SEP
- split water with 20 MWe into H2 and O2, store
- return to HEEO

on another note...

The same design could be later “upgraded” to NEP for outer solar missions (beyond Asteroid belt). Put reactor back on the “nonliving” part of the truss, replace solar cells with radiators and you have 20 MW NEP. All of the things needed for SEP would be needed for such NEP anyway. Docking, high isp, thrusters, power, storage, rotating structures, deep space missions,.. What you don’t have to develop right now is reactor, converter and radiators. You must only know how to put solar panels on it, and we know how to do this (Deep Space 1 flew with those panels).

Disel is just and example. It can be anything that can extract energy from fuel and oxidizer. That can be internal combustion engine, gas turbine, fuel cell,..

At KW - MW power levels you can't carry enough solar cells with you. And there is no need to. Your power source in the base allows you to make methane/oxygen (or any other combination). When you return to base you simply refuel.

Rotation would be in the range of 1 - 3 RPM. At 200 m, the coreolis and gravity gradient problems should be minimal. I have read repots that humans could adapt up to 10 RPM if the change would be done gradually. If there would be any problems (what kind of problems?), crew could still travel at 0 g with stationary SEP tug. The tug itself does not need rotation to function.

I think the precise targeting could be done, but it would require more mass to make everything stiffer. The question is if carbon laced hydrogen could get isp in the range of 3000 – 5000 seconds to make everything worth it. that's the unknown.

But if not, then it could focus solar energy onto a big, well protected from radiation, cooled, high efficiency solar panels or some other heat to electricity converter. This would require a lot less precision and there are many electric propulsion methods that can be used. Electrical energy could power something like direct drive hall thruster. Something in the range of 1 - 10 MW would be quite possible and could do most of the interorbital transportation for the fraction of a propellant ($$$) needed otherwise.

0.6 MW SEP tug: http://www.entechsolar.com/SLA-SEP-WCPEC4.pdf
5-10 MW NEP mission to mars: http://gltrs.grc.nasa.gov/reports/2006/ … 214106.pdf

It's easier (and cheaper) to add one diesel engine and two gas tanks than to build and check thousands of km of rails. Especially since we are talking about 0.37g, airless environment with limited amounts of workers.

Broken railway would need immediate attention (because everything on that rail would lose power).  If one road train breaks down, the rest of them can easily bypass it, while the truck gets towed back to the garage for repairs. Diesel engines could get checked and fixed at sheltered garages at regular intervals (when there is nothing more urgent to be done).

I don't think that making trucks drive themselves would be that much of a problem. We can already do it on the Earth, but we don't because of legal problems (who is to blame when something goes wrong?). Since Mars is empty and will be short on people (that will be able to drive trucks) and since any accident could be deadly for a driver (broken window = suffocation) the trucks will be automatic. It could get lost, but then again it could also go to places that do not have rails laid down. It’s simpler to make good maps than to make tons and tons of steel rails.

The rails could be used to transfer electricity, but I don't see any need to transfer electricity to begin with. It's not like there are hydroelectric plants on Mars that are away from "populated" areas. Power = solar, nuclear, stored (from the first two). So no need to transfer big amounts of power since it would have to be produced where it is needed. If the power lines would be needed it would be cheaper/safer to make power lines.

If it can handle more cargo but travel slower, than it's the same capacity. If you are in a hurry than you can always fly on the mars.

fly.

If you will plan whole trajectory and mission, then you could split travel into two parts.

a) From LEO to high earth orbit (2:1 moon synchronous orbit, L1, L2, HEEO,..). This part of the mission would be time insensitive (it could wait in final orbit) and could be made unmanned (The crew could arrive from Earth in few days on a Orion/Soyuz type of ship), since it will travel though Van Allen belt radiation. This part would need 3 - 3,8 km/s delta-v, which is 2/3 of the needed delta-v to get to Mars from LEO.

b) From high earth orbit (near Earth Escape velocity) to Mars. To get from there to Mars transfer orbit you would need around 1 km/s delta-v. This part could even use moon fly-bys to reduce needed delta-v. Capture to Mars orbit or Mars surface could be made with aerobraking or with low thrust/high isp engine. Orbits around L1/L2 would allow greater flexibility while the elliptical earth orbits would need smaller delta-v to reach.

This might help: http://en.wikipedia.org/wiki/Delta-v_budget

What is wrong with "strong, big, light weight collector"? I added the link to the proposed solar thermal tug, that would use such collector and I don't see any big problems with it.

It's thin film with some kind of structure that holds that film in place and in the right shape to reflect lots of light. It must be strong enough to hold it's shape in weightless and airless environment. Is this really that much harder than say.. building nuclear reactor?

It's cheaper. I have nothing against nuclear, but why build expensive nuclear reactor if sun always shines in space. My guess is big balons with plastic film would be more cheap, less prone to problems and safer (safer as in it can't explode on launch from earth and having "Another Chernobil!!" reported on every TV and newspaper). If one gets damaged, just inflate another one instead.

There is no need for high Isp AND high thrust. You do need high isp so that more of your spaceship is spaceship itself and not propelant, but high thrust can be replaced with longer thrusting times. The trip to Mars would take months anyway so why not use that time to change trajectory with high isp propulsion of the spaceship so that actual insertion would need minimal delta-v.

sure you do need 4-5 GW.. if you want to use your rocket few minutes, burn all your propelant and then do nothing for few months while you drift in space..

To get to Mars from LEO, you can start your GW reactor, heat hydrogen, get "rocket like thrust" and get enough delta-v (3,2 km/s for Earth Escape velocity + 0,6 km/s to get onto Mars Transfer Orbit) in few minutes, dump your "empty" reactor and then aerobrake into high Mars orbit (- 0,9 km/s), low Mars orbit (- 1,4 km/s) or even to Mars surface (- 4,1 km/s). On the way back you dock to spaceship in low Mars orbit, do another thrust (1,4 km/s + 0,9 km/s), drift for few months, dump transfer stage and aerobrake the crew back to Earth.

Or.. you can start in LEO, slowly spiral (3,2 km/s) to high earth orbit (that can be done unmanned because of van allen belt radiation), launch crews seperatly (Orion?), dock with waiting spaceship in L1, L2, HEEO or any other high earth orbit, add a little thrust (0,2 km/s) and you are on your way to Mars. Few months needed for transit is used to change orbit (0,6 km/s + 0,9 km/s) so that you get captured into High Mars orbit when you arive. After that your crew can land on Mars surface while your spaceship waits in High Mars orbit (or even spirals closer to Mars for easier access from Mars surface). When it's time to return from Mars back to Earth, your crew leaves Mars surface (4,1 km/s), docks (1,4 km/s) your waiting spaceship, leaves Mars orbit (0,2 km/s), use the rest of the months changing your orbit (0,6 km/s + 0,9 km/s) so that when you arive your spaceship enters high Earth orbit, while your crew aerobrakes back to Earth (with Orion?). Bonus: you keep your spaceship and only need to refuell it to go to Mars again.

The only things that need high thrust transfers are crew transfers and that can be done "the old way" with chemical rockets. Most of the heavy stuff can be moved with high isp and relativly low thrust. And it fits "don't mix crew and cargo" philosophy..

If we can point Hubble within 0.1 arcsecond of a distant star I am sure we will find a way to focus sunlight. It doesn't even need to be perfect focus (we will not use it to look at different stars)..

I am sure this problem could be fixed with simple swich, that would stop your supply of Hydrogen, if supply of energy is interrupted.

Acceleration would be trivial, if the thrust would be minimal.

water is easier to handle, but if heated to high temperature it breakes into Hydrogen and Oxygen. That Oxygen reacts with anything it touches.. unless.. it's plasma and it doesn't touch anything (it can be controled with magnetic fields). If you get plasma hot enough it would have high speed (= high isp). Thrust is another matter, but I am not worried about it. More energy at the same isp = more thrust, so to increase thrust you only need to add more energy. You can't increase isp because you are limited by the temperature of your heat exchanger. Unless you don't use heat exchanger and you heat gass to the point it becomes plasma. Kind of like GCR only that the core would be heated by super concentrated sunlight and not nuclear fission.

So, Would high isp be possible?

I was reading some pages about solar thermal propulsion. It’s relatively simple, has moderate isp (800 – 1200 s with hydrogen) and it could be used for slow transfers. Solar thermal works like this:

Proposal for solar thermal rocket: http://www.stg.srs.com/atd/STP.htm

But to be really useful it would need higher isp (around 3000 s) and preferably use anything as the propellant. That would mean basically that gasses would have to have higher temperature as they would leave rocket chamber without melting rocket chamber. (= max 1200 s) Higher temperature = higher speed = higher isp. Then I saw this two pictures for Laser Thermal Propulsion:

Could something like this be used only that instead of the laser we would use the sun as the source so the light?

Since sun is that far away it's light could almost be treated as the laser beam (very weak one). Use multiple big, lightweight solar concentrators that would get as much solar energy to focus one point (through the series of mirrors) that it would instantly create plasma from anything that would be there (up to 1 GW of solar thermal power?). Once we would have plasma we could control it like we control any other plasmas with magnetic fields (something like Vasimr).