Monday, December 10, 2012
Sending humans in a SpaceX Dragon v2 capsule to EML-1 or 2 is a worthwhile possible step in a 100% commercial return to the Moon. The SuperDraco thrusters to be included in the sidewalls of the crew Dragon capsule are more than capable of performing the trans-lunar injection burn, as well as station keeping at the Lagrange point, rendezvous with any preemplaced assets - such as a lander - and returning the crew to Earth.
The total delta-v for such a bare bones mission to EML-2 is a mere 4835 m/s. EML-1 is similar. This is a "quick transit" 4-day trip up to EML-2, so the crew spends less time in the radiation belts. A good estimate of the dry mass of the Dragon v2 is 8000 kg. Using an isp of 320s, the initial mass in LEO is just 37344 kg, or 68% of the maximum payload mass of a Falcon Heavy.
Just going to a Lagrange point with a crew on Dragon would be a momentous achievement and could be done for a mere $150M. However, it is just the first step.
If we fill the remaining Falcon Heavy payload mass with fuel, the total delta-v available to the Dragon becomes 6050 m/s. This is sufficient to go from LEO to EML-2 to low lunar orbit and back to Earth, with significant margin for maneuvering and rendezvous, if required.
What might the crew in the Dragon rendezvous with at EML-1, EML-2 or low lunar orbit? Using the same SuperDraco thrusters to take the slower 9-day transit - a delta-v of just 3470 m/s - 18.2 tons of payload can be delivered to EML-2. This payload can loiter for months waiting for the crew to arrive. Up to 14.8 tons can be deployed from EML-2 to low lunar orbit when required. Up to 6.2 tons can be landed on the surface if the lander is taken via low lunar orbit, or up to 8.1 tons if taken directly from EML-1 or 2.
This is all possible because I have avoided two pitfalls of lunar return architectures that have become very common in recent years.
Firstly, I have ignored the possibility of using the second stage of the Falcon Heavy to perform any part of the trans-lunar injection burn. A simple trade study shows that it is not advantageous when you have sufficient thrust on the payload - which you must have to do later maneuvers - so I'm baffled as to why people keep considering it.
Secondly, I have not used any high isp propulsion such as LH2/LOX or CH4/LOX. Although this may become preferable in future lunar architectures (especially if propellant made on the Moon becomes available), it is currently an additional expense which does not provide significant advantage to justify its cost.
Friday, October 19, 2012
For simplicity, I will assume a two ton single stage lunar lander with additional drop tanks. I'll use a self-pressurizing mixed monoprop, like NOFBX from Firestar (isp 320s). Starting in LEO the vehicle will perform three burns (3107m/s, 3140m/s, and 2890m/s), not stopping in lunar orbit and dropping tanks after each burn.
Hopefully, SpaceX will kick in some PICA-X for the heat shield, which will be mounted on a Mercury-sized capsule. The lander will look much like the Odyssey/SpaceX/Firestar alternative that was floated during the NASA Altair studies.
suitport to explore the surface. This removes the need for an airlock, saving mass, and exposure of the cabin to vacuum, simplifying the design.
The total cost of the mission will be around $150 million.
Tuesday, September 25, 2012
NASA recently announced their Gateway station for beyond LEO exploration to the wider press.
This is not news to the space advocate community with articles going back to December of last year. Even so, now is the time when this concept will be received by the politicians as "new". Soon, they will be introduced to the Gateway as either being a part of their plan or something which challenges it.
Many space advocates have complained that the central element of NASA's beyond exploration plan - the Space Launch System - has no payloads, or costs so much that no payloads can possibly be developed to fly on it. The obvious exception to this has been the Orion crew capsule, which is simply seen as too expensive compared to commercial crew offerings. Congress could see the Gateway station as the answer to this criticism.
That would be a good thing - whether you like the Space Launch System or not. The reason is simple: there's nothing else. Up to now, the plan has consisted of flying an Orion capsule around the Moon and coming home. After that.... maybe going to some asteroid someday, no idea which one, or when, and then going to Mars somehow.... well, they haven't thought that far ahead.
The Gateway station, should it ever be built, provides a place to go, and perhaps more importantly - it provides a place to stay. This is exactly the kind of space architecture that many advocates have been talking about for years. Critics of the Space Launch System and even the former Constellation program have always said that NASA should be working on building in-space architecture like this from which to stage reusable lunar exploration. The Gateway is also ideal for launching missions to Mars.
Any space station needs supplies and with the success of the Commercial Orbital Transportation System for delivering cargo to the International Space Station, NASA will be looking to commercial providers for resupply services.
So why would politicians be against the Gateway station?
Primarily because it doesn't require a really big rocket like the Space Launch System. The individual components of the Gateway station are no bigger than the modules used on the International Space Station, which was built without the need for a "monster rocket". One plan for building Gateway involves assembly and checkout at the International Space Station with a slow boost up to the far side of the Moon using electric propulsion.
Now, please don't take this the wrong way, but it is exactly at this time that critics of the Space Launch System need to shut up about it. If Congress catches wind of the non-critical nature of their monster rocket in this plan, Gateway will be as welcome as a fart in a spacesuit.
Do you hear what I'm saying?
Wednesday, July 25, 2012
Did you miss the philosophy lessons?
Gather 'round young ones, let's sit on the grass and discuss the beliefs that make men build planes when they really want to be building rockets.
Way back in the 70s, the realization that space would never be a frontier until launch costs had been reduced led many to pin their hopes on the Space Transportation System, and later on the only surviving component: the shuttle.
During the 80s, it became obvious that the shuttle would never achieve a reduction in the cost of access to space and, in fact, NASA had stopped claiming that this was the goal of that program.
During the 90s, various rag-tag efforts were made to turn LEO and MEO commsat launch into a massive market which would require the kind of launch capability that only a fully reusable vehicle could service - something like the mythical DC-X that many believed was killed for challenging the Shuttle.
Some say they actually succeeded.. others say they only succeeded in getting funding for the development of the launch vehicles. In either case, some money started flowing into the industry and attempts were made, using the best technology and techniques of the day, to finally, sincerely, make a reusable launch vehicle.
The boom led to the crash, as it inevitably does with capital mal-investment, and many recognized that they never had a chance of success. Although there are still some who say that simply not enough money was spent, there are cooler heads - because they are more humble - who say they simply didn't have the talent or the technology in-hand to make a good go of it.
Depression set in for some time, but eventually leaders emerged. They suggested that perhaps there was another market that could be serviced by a reusable launch vehicle - a market which is more tolerate of risk, more price elastic, and ready to fly immediately. Perhaps there is a market in which an unskilled team could start slowly, build experience of actually flying and make money along the way. That market was space tourism and, like a wave, it would carry a company from the ground, to the air, above the atmosphere, into orbit and beyond - if they could hold on.
But I go on, look at the time, we should go inside before it starts raining.
Sunday, June 24, 2012
I would like to submit a Walking Eagle Award nomination for the Ad Astra Rocket company for their "Human Transportation to Mars" concept.
The primary basis of my nomination is the size of the nuclear reactor proposed, but even if such a reactor and all the other support infrastructure to launch the mission from an Earth-Moon Lagrange point was available, and their propulsion technology actually worked, I think there is a very strong argument that such a fast transit decreases mission safety because it eliminates the free-return-trajectory abort mode.
The only nuclear reactor the US has ever flown in space is the SNAP-10A, which produced a mere 650 watts of electrical power, from 45 kW of heat. The SP-100 reactor program, which were never flown, was to produce 100 kW of electrical power from 2 MW of heat. The Russians flew reactors which produced 3 kW to 5 kW of electrical power, and built some 40 kW reactors that were never flown. So when Ad Astra baselines a 200 MW nuclear reactor, they're talking about a reactor 40,000 times as big as anything that has ever flown! It's even 2000 times as big as anything anyone has ever tried to build, and 5,000 times as big as anything that has ever been actually built!
There are other arguments against a nuclear reactor of this size, relating to the power per kg and the size of the radiators that would be required, however as it is obvious that no such reactor will be available, they are superfluous.
Need I say more?
Okay I will. Come with me now as we enter the fantasy land where electrical power for the VASIMR thruster is free and plentiful. Perhaps we have a nuclear fusion reactor that works in space and doesn't require any heat radiators, etc. Also, we have superconducting magnets that work at space temperatures, and all this technology is ready. Also, there's scientifically literate politicians both in the White House and the Congress and the US has paid off their national debt with the profits they received from selling ponies to North Korea.
As pointed out by Bob Zubrin last year, hurtling towards Mars at breakneck speed means you better be successful at stopping or your crew goes cruising off into the outer solar system never to be heard from again. In a six month transit, which has already been achieved using modest chemical propulsion, the crew has the option of aborting back to an Earth returning trajectory. How is throwing away this abort mode in the name of making the trip safer a good idea?
Also, their rocket doesn't actually produce any thrust.
Friday, March 09, 2012
In a recent interview Rand Simberg comments:
He was not just referring to the current government efforts at human spaceflight, but also to the growing concern with safety by private spaceflight providers. Just how important is commercial spaceflight?
At a recent hearing of the House Committee on Science, Space, and Technology, Rep E.B. Johnson (D-Texas) answers:
There is no question that "joyrides" are being offered to wealthy people to help fund the development of suborbital (and eventually, also, orbital) spacecraft.. setting aside the fallacious attempts by Rep Johnson to suggest that this is somehow the government's purpose for funding commercial crew efforts, is this alone an important enough purpose to risk human life? Are there pilots willing to fly such craft multiple times, knowing full well the risks they are taking, and the purpose for which they are flying and, if so, why?
The simple answer is yes and because.. well.. because they get paid. (I've been reminded that many pilots would fly for free if they were given the option.. so what? Whatever their motivation is, that is adequate compensation.) Economic activity has the unique and amazing attribute that those like Rep Johnson will never understand: it is engaged in voluntarily. How much risk to human life is acceptable? As much or as little as the market is willing to tolerate. Logically, the importance of opening the frontiers of space can be similarly determined.. but only if a free market is allowed to function.
Wednesday, March 07, 2012
I'd like to suggest this is an extreme response and describe how something akin to copyright is valid in a free market, libertarian society.
The fundamental basis of libertarianism is private property. In this theory there can be no question that the correct and proper owner of work is the creator of that work. (A possible caveat is that all the inputs to the work were already owned by the creator - if you create a sculpture out of my marble, not only is that sculpture mine, I may have recourse against you for using the marble without my permission.) In terms of homesteading, the creator of a work has a greater claim than any subsequent claimant as they are, from the point of view of the creator, latecomers.
The basis of private property is the self-ownership concept. I am well within my rights to offer to sing a sonnet for you, in exchange for a mutually agreed price. Our agreement is called a contract, and it is of no business of any third party what the terms of our contract are. This would appear to be an argument for intellectual property, such that sonnets are works of the mind - and some have argued exactly that - but I think we need to go deeper.
What kind of price might I demand for my performance? In a free market, the answer is clear: anything the market will bare. If I so desire, part of the price I demand can be secrecy. If my audience is not willing to meet my price, they have no right to hear my performance. In a sense, I have prevented reproduction of my performance, not by the skill and grace of my voice (trust me, there isn't any), but by the contractual arrangement under which it was given.
This method continues to function if the intellectual work is provided in a fixed form.. be it written on paper, painted on a canvas, etched into a sculpture, or encoded in a computer program. If I require the purchaser to maintain secrecy, or even just refrain from making copies, then I have a legal recourse if the contract is subsequently broken.
One may object on semantic grounds to the use of the word "purchase" when referring to a contract of this sort. While it is clear that the purchaser of a performance is not buying the performer, it is less clear that the purchaser of a sculpture which comes with restrictions on its use, is indeed "purchasing" the sculpture. If it helps, one may reasonably say that the sculpture isn't being purchased at all - it is only being rented, and comes with a rental agreement that includes some restrictions. This would be a fair characterization.
We can now anticipate what will happen if the contract is violated. As it is absurd for a sucker who buys a rented car to expect to be able to keep it, so too any receiver would be amiss to believe he could keep a copy of our rented sculpture. His grudge at having his copy removed from him would belong to he who sold it to him. As in all property disputes, a claim of title passed from seller to buyer is required to prove legitimacy. Any receiver wanting to keep his copy would present such a title, allowing the trace back to the original contract violation by the ultimate culprit, no matter how many copies were made.
Under such a Liaise-fair copyright system, the costs of enforcing a copyright belong with the owner of the original work. However, just as with all other contracts, the courts are at his disposal to enforce his correct claims.
This is not to imply that such a system would necessarily be successful. It is simply a given of free societies that contracts are voluntary. Upon reading a contract with a copyright clause such as this one, a trader may choose to seek goods from elsewhere. The success or failure of such a system as this one would be decided by the state of the market in which it is attempted. This is as it should be.