Low-cost Launch Vehicle Concept

[K^2]

Yeah, maybe I was overestimating with 1 ton of tug propellant for each supply run, but the tug still needs to be refueled, and that will take a significant chunk of the total payload capacity.

That's not estimating. That's just guessing. Round trip would take less than 300m/s of dV for the tug, which is less than 10% of exhaust velocity of non-cryogenic fuels, which results in dm of under 10%. Even including mass of the tug and the engines, 200kg would be an extremely paranoid upper bound for the fuel you need to use up. So if we look at the worst case scenario, going with 2M/launch, only 800kg usable, and 1/3 rockets going boom, we still get $3,750/kg, which is considerably cheaper than any existing alternative. (F9 is well over $4,000/kg)

And this is as bad as it could possibly get, according to all of the information available. Realistically, we are looking at a far more favorable cost/kg.

[Nibb31]

Thanks for the math... I'm still not convinced that an upmass of 800kg is worth bothering with for ISS operations, and even less for a fuel depot, even if the cost is low. It adds a lot of mission complexity, which also has a cost and an impact on ISS operations.

A bicycle is much cheaper than a semi-trailer, but if you need to move 10 tons of apples, it will be more practical to do it with a truck than to do 100 runs with a couple of apples in your pocket, regardless of how cheap the bicycle is.

Also, SSTOs tend to have a pretty abyssmal payload fraction. If you can make a cheap expendable SSTO with a 1-ton payload, why couldn't you make a 2 stage rocket with the same technology for twice the cost, but with a 3 ton payload?

[Albert VDS]

Also, the astronauts/cosmonauts on the ISS already have a busy schedule.

In 2013 the total resupply mass was about 16300 kg, spread over 8 missions.

It would take 21 missions to send that amount with the Aquarius.

That's almost 2 missions every month.

Now imagine the logistics of that:

Getting your payload to the rocket.

Launching the rocket.

Rendezvous with the tug.

Rendezvous with ISS.

Decouple and de-orbit.

Imagine how long a normal birthing takes, thats a lot of time wasted.

[CalculusWarrior]

Thanks for the math... I'm still not convinced that an upmass of 800kg is worth bothering with for ISS operations, and even less for a fuel depot, even if the cost is low. It adds a lot of mission complexity, which also has a cost and an impact on ISS operations.

A bicycle is much cheaper than a semi-trailer, but if you need to move 10 tons of apples, it will be more practical to do it with a truck than to do 100 runs with a couple of apples in your pocket, regardless of how cheap the bicycle is.

Also, SSTOs tend to have a pretty abyssmal payload fraction. If you can make a cheap expendable SSTO with a 1-ton payload, why couldn't you make a 2 stage rocket with the same technology for twice the cost, but with a 3 ton payload?

Staging does increase complexity (and thus cost) of rockets; you're probably looking at more than just twice the increase in price.

[sgt_flyer]

One of the issues i have is that they only seem to take into account the 'rocket' part. But for it to work, they will require an orbital depot, and maybe several different tugs if they stock up the goods in a depot, then ferry a big quantity to your customer in one go. (Because a common tug ferrying 1-ton payload and 5ton payload would have to be 'average' - not good at either - and would spend more fuel than needed for 1 ton payloads (because it's dry weight would be higher than a dedicated tug for 1 ton payloads)

Also, they don't take into account the time and cost of devellopment for all of those systems. (Unless they plan to buy ESA's or russians existing automatic docking systems) - especially today, with upcoming low cost systems already in the works (reusable spacex falcon, skylon, etc) the technology they want to create is interesting, but i'm wondering about it 's effectiveness/real costs of how they envision it would work

[Kerbin Dallas Multipass]

I'm also wondering about the hidden costs of the space tug. How much would be the cost of development, certification etc? What would be it's lifespan in terms of time and docking cycles? Any malfunction in the tug could potentially cause a crash with the ISS, and maintenance and checkups are probably impossible between docking maneuvers. So how many docking cycles are we talking here realistically?

Another thing is logistics: Payloads of existing support vehicles are not only limited by mass but also by volume. So, from what I hear, they like to mix "expensive" cargo (spare parts, experiments) with "cheap" consumables in order to use the available mass and space in the best possible way. Having an extra vehicle just for the milk runs such as the Aquarius might render this game of Tetris more difficult for the other vehicles, possibly reducing their payload efficiency.

[K^2]

Thanks for the math... I'm still not convinced that an upmass of 800kg is worth bothering with for ISS operations, and even less for a fuel depot, even if the cost is low. It adds a lot of mission complexity, which also has a cost and an impact on ISS operations.

A bicycle is much cheaper than a semi-trailer, but if you need to move 10 tons of apples, it will be more practical to do it with a truck than to do 100 runs with a couple of apples in your pocket, regardless of how cheap the bicycle is.

I don't think you understand the concept of cost-per-launch. The reason that it's cheaper to move apples by truck is that cost of hiring an operator is comparable to cost of fuel, and cost of equipment is kept low due to it all being very reusable. So your biggest loss on running hundreds of couriers with bicycles is money you'd be paying to couriers. The cost-per-delivery of each apple includes all that and ends up being way cheaper with a truck. But now imagine a situation where you have to throw the truck/bicycles away after single run, and people are poor and work for peanuts. Now it's just a matter of fuel consumption and cost of equipment, and bicycles are just so much cheaper that you'd be a very bad businessman to pay for a truck.

All of these considerations are included in the cost-to-launch. When you put it all together, the final price of putting 1kg of cargo by either method is all that matters, and with such cheap launches, the final price does end up lower despite all of the problems you've been talking about. Because, again, all of this is included in the price tag.

From perspective of ISS, this doesn't have to be any more complicated either. Tug can be fully autonomous and collect all of the cargo from multiple launches a safe distance from ISS. Then operators at ISS would take that cargo, using the same tug, all at once to the ISS. No different than getting a shipment from one of the Progresses. This can work even better for a fuel depot, because one of these can be 100% autonomous from the start. So who cares how many round trips the tug will have to make, or how many launches you have to make. The final price of fuel in orbit is lower than if you used an expensive, reliable rocket. And that's all that matters in the end.

[NikkyD]

I think the cost of a rocket launch is more than just the rocket and fuel. You need good weather, secure the site, have lots of ppl on standby etc. So the idea of multiple small launches is probably more expensive than you would think.

[Albert VDS]

No matter how good this tug might be, I doubt it would be allowed to automatically dock with the ISS.

So it's still taking valuable time from the ISS crew.

[Nibb31]

I don't think you understand the concept of cost-per-launch. The reason that it's cheaper to move apples by truck is that cost of hiring an operator is comparable to cost of fuel, and cost of equipment is kept low due to it all being very reusable. So your biggest loss on running hundreds of couriers with bicycles is money you'd be paying to couriers. The cost-per-delivery of each apple includes all that and ends up being way cheaper with a truck. But now imagine a situation where you have to throw the truck/bicycles away after single run, and people are poor and work for peanuts. Now it's just a matter of fuel consumption and cost of equipment, and bicycles are just so much cheaper that you'd be a very bad businessman to pay for a truck.

Note that I used the word "practical", not "economical" for my analogy. The rocket itself may be cheap and unreliable, but anything approaching the ISS, however small and automated, is going to be under high scrutiny, because there are human lives involved and billions of dollars of investment. So the actual rendez-vous, docking, and transfer manoeuvers will have to follow the same procedures as any ISS supply craft. Unfortunately, those mission control people don't work for peanuts.

From perspective of ISS, this doesn't have to be any more complicated either. Tug can be fully autonomous and collect all of the cargo from multiple launches a safe distance from ISS. Then operators at ISS would take that cargo, using the same tug, all at once to the ISS. No different than getting a shipment from one of the Progresses. This can work even better for a fuel depot, because one of these can be 100% autonomous from the start. So who cares how many round trips the tug will have to make, or how many launches you have to make. The final price of fuel in orbit is lower than if you used an expensive, reliable rocket. And that's all that matters in the end.

That's not how ISS operations go. Progress or ATV are already automated, yet they need to be monitored because things can go wrong and a docking mishap could be catastrophic. You still need someone sitting in the Cupola with their hand over the big red Abort button. You still need a day or two of preparation to rotate the station to its docking/undocking attitude. You still need a team in a mission control center handling tug operations and monitoring the telemetry. The arrival of a supply vehicle, even a fully-automated one, is an "all hands on board" situation for the ISS crew, because safety is critical.

Another thing that hasn't been thought out is the actual docking hardware. I'm having a bit of trouble imagining a docking system that can dock a pressurized toroidal payload module and still allow access to the sandwiches that are inside, while remaining simple enough to be dirt cheap, and reliable enough to be used with humans in the loop. It seems to me that putting the payload on top of the rocket would make the design much more straightforward.

Edited January 27, 2014 by Nibb31

[MaverickSawyer]

Just glancing through the pdf...

WHY ARE THEY USING LOX AS THE ENGINE COOLANT!!!!!!

-LOX has a lower heat absorption rate than LH2.

-LOX in contact with the high-temp chamber walls is a recipe for a SERIOUS RUD. EVERY. DAMN. TIME.

[Kryten]

No matter how good this tug might be, I doubt it would be allowed to automatically dock with the ISS.

So it's still taking valuable time from the ISS crew.

Why? ATV, Progress and Soyuz all currently dock automatically, with crew intervention only a contingency.

[Kerbin Dallas Multipass]

Why? ATV, Progress and Soyuz all currently dock automatically, with crew intervention only a contingency.

It's possible, but the certification process is very lengthy and painful.

[K^2]

That's not how ISS operations go. Progress or ATV are already automated, yet they need to be monitored because things can go wrong and a docking mishap could be catastrophic.

Again you've missed the point and the big picture. The tug can take the 1T payloads to a location near ISS. 100% automatic. No involvement from ISS crew necessary, because no danger to ISS is presented even in an event of an error. When enough cargo is assembled at the nearby location, that same tug can take all of it to the ISS in one bulk. This stage is monitored from station, same as Progress. It will deliver many tons of cargo, same as Progress. The tug will have automatic controls with manual override if something goes wrong, same as Progress. The only difference is that the total cost of getting that cargo to the station is significantly lower. That's after we include all of the additional hassles.

You keep insisting that there are downsides, but absolutely none of them are backed up by any numbers. Indeed, numbers contradict your statements time and time again.

[sgt_flyer]

@K^2 mmh, ferrying an assembly of several torus shaped modules, you would end up with almost no possibilty to pressurize them reliably for a low cost.(also, you'll want the ISS docking system on the tug and not the payload to keep costs down.)

So, payload possibilities :

ISPR's, which could handle being in unpressurized environments would be out of question as a payload (their shape would prevent it - not accounting for how valuable their content is) so that leaves fuel,food, hand tools and consumables. Food, hand tools and consumables are much more easily extracted from a pressurized environment (much easier on the astronauts) - so for having all the separate modules pressurized and with a manhole between them reliably would be very hard to do cheaply.

So in the end, the only thing it would be very good for, would be for ferrying fuel...

[Kryten]

It's possible, but the certification process is very lengthy and painful.

Why would anything new need to be certificated? It'd have to use the Russian docking ports to transfer fuel anyway, why not just use the standard rendezvous and docking hardware in the same way as the ATV?

[K^2]

@K^2 mmh, ferrying an assembly of several torus shaped modules, you would end up with almost no possibilty to pressurize them reliably for a low cost.(also, you'll want the ISS docking system on the tug and not the payload to keep costs down.)

Inflatable shell to contain cargo can be deployed for peanuts compared to launching a pressurized ship with the same amount of cargo. And this shell would only have to be launched once, and it can contain all the docking adapters you need.

You are really making it more complicated than it needs to be. Certainly, some amount of work has to be put into all of this, but we are contrasting it to hundreds of millions of dollars worth of cargo launches yearly, and cutting prices on these anywhere from 25% to 75% easily. Put five years of savings from this aside and you can organized a manned mission to the Moon, for crying out loud. And you're worried about docking certification. Bah!

[Kerbin Dallas Multipass]

Why would anything new need to be certificated? It'd have to use the Russian docking ports to transfer fuel anyway, why not just use the standard rendezvous and docking hardware in the same way as the ATV?

It's not just about hardware. The entire procedure (hardware, software, communications) has to be certified, abort modes have to be proven etc. ISS operators seem to be ultra picky about this - understandable as someone mentioned above, since human lives and multi billon dollars are at risk. I listened to a podcast with the (an) ATV project leader where he's talking about this (german only http://raumzeit-podcast.de/2011/06/17/rz017-automated-transfer-vehicle/ )

In the age of privatized spaceflight you can't just go and "take" some other organization's or company's tech and just plug it into your competing rocket.

[sgt_flyer]

Well - in the end, talking about aquarius is a moot point, as it was not selected by COTS. Although i hope the vortex engine research are still made - this technology can help lower the costs of other rockets if the engine becomes reliable.

One final thought, the page on astronautix tell aquarius would need to be launched 100 times a year to achieve it's low costs. (accounting for losses, so 66 effective launches)

anything less, and they will have to up their prices for compensate i guess.

That still make 1 launch roughly each 8 days - that's quite a lot (a huge infrastructure behind it would be needed to produce 1 rocket per week)

(And hoping the rocket systems does not fail while it's in orbit - else, that would make a really huge debris

Edited January 28, 2014 by sgt_flyer

[K^2]

And hoping the rocket systems does not fail while it's in orbit - else, that would make a really huge debris

That seems to be part of the reason why there is a dedicated parking orbit, rather than delivering cargo to destination orbit directly. Debris from failure bellow 200km would decay fast enough to not be long-term concern.

[shynung]

Just glancing through the pdf...

WHY ARE THEY USING LOX AS THE ENGINE COOLANT!!!!!!

-LOX has a lower heat absorption rate than LH2.

-LOX in contact with the high-temp chamber walls is a recipe for a SERIOUS RUD. EVERY. DAMN. TIME.

In the engine diagram further in the PDF, it is shown that the LOX, now gas,travels through the combustion chamber in a vortex (hence the name) after the cooling jacket. This vortex protects the chamber walls from the combustion itself, keeping its temperatures low.

I think the decision to use LOX as coolant has something to do with the engine's use of hydrogen gas (boiloff of the LH2), but I do not understand the specifics of the matter.

[Albert VDS]

Why? ATV, Progress and Soyuz all currently dock automatically, with crew intervention only a contingency.

And everyone on the ISS is doing something else, ignoring the whole automated procedure?

[Kryten]

And everyone on the ISS is doing something else, ignoring the whole automated procedure?

Usually, yes. There are two control centres full of people meant to do that kind of thing.

[K^2]

In the engine diagram further in the PDF, it is shown that the LOX, now gas,travels through the combustion chamber in a vortex (hence the name) after the cooling jacket. This vortex protects the chamber walls from the combustion itself, keeping its temperatures low.

I think the decision to use LOX as coolant has something to do with the engine's use of hydrogen gas (boiloff of the LH2), but I do not understand the specifics of the matter.

It's not even chamber walls. I'm more worried about LOX being used to cool the nozzle bell. These are small channels at high temperatures that are going to carry one of the most corrosive substances possible?

On the other hand, I see no reason why LOX and LH2 can't be simply switched here.

[Nibb31]

Usually, yes. There are two control centres full of people meant to do that kind of thing.

There are usually at least one or two astronauts watching the docking procedures.