Propulsion in space is an extremely tricky affair, one that’s centred heavily on trade-offs. The engines we use to get into space are woefully inefficient due to the large amount of propellent that has to be taken along with them. The faster/further you want to go the more propellent you need which makes the rockets increasingly bigger, putting a soft upper limit on what makes for a feasible craft. On the flip side once you’re in space we have engines with efficiencies that are so good that they can achieve incredible speeds with fractions of a percent of the fuel that it takes to get them into orbit. It’s no wonder that these engines were chosen for the Dawn mission to Vesta and Ceres.
There’s also engines that straddle the boundaries of these two like the VASIMR which aren’t capable of getting payloads off the surface of the earth but are quite capable of performing the same tasks as chemical rockets in space with a fraction of the required reaction mass (fuel). The trade off here is that it requires a rather large power source for it to be effective, on the order of hundreds of kilowatts, which means that in order for it to fly you need an ultra dense power source, usually in the form of a nuclear reactor. They’ve also never been flown on an operational mission yet (they have been thoroughly tested and verified however) but we will likely see one aboard the International Space Station within the next 3 years or so.
Barring some technological breakthrough I was pretty sure these engines were going to be the ones powering most of our craft for the next couple decades or so as we’ve got most of the bases covered. However it turns out that there might be a way to improve on the high efficiency/low thrust idea by doing away with the reaction mass completely. Sounds impossible right? I mean what engine can run without any fuel to drive it? As it turns out there’s quite a lot of energy to be derived from the vacuum of space and NASA are investigating how to tap into it:
The lab will first implement a low-thrust torsion pendulum (<1 uN), and commission the facility with an existing Quantum Vacuum Plasma Thruster. To date, the QVPT line of research has produced data suggesting very high specific impulse coupled with high specific force. If the physics and engineering models can be explored and understood in the lab to allow scaling to power levels pertinent for human spaceflight, 400kW SEP human missions to Mars may become a possibility, and at power levels of 2MW, 1-year transit to Neptune may also be possible
Essentially the way a QVPT works is by harnessing the random fluctuating magnetic fields that are present throughout the vacuum of space and using them to propel the craft. This works by polarizing a block magnetoelectric material leading to a force in one direction on the block whilst the field, or more accurately the bosons they’re made up of, are pushed in the other. Technically QVPTs are drives that uses photons as its reaction mass but it doesn’t have to bring them along which is a pretty big distinction between them and ion thrusters.
Much like VASIMR and ion thrusters QVPTs main limitation is the size of the power source that they can bring with them. However unlike their predecessors QVPTs have a far greater upper limit on how long they can run (referred to as specific impulse). These means for long distance missions like those to Mars and beyond there’s great potential to cut much of the transit time off by utilizing a QVPT. To put it into perspective the fastest craft ever launched, New Horizons, will take approximately 9 years to reach Pluto at its current speed. A QVPT powered craft is theoretically capable of getting there in just on a year, almost an order of magnitude faster. Of course this will rely on the effect being experimentally verified but since NASA has dedicated an entire team, dubbed EagleWorks, to verifying the idea I’d say that there’s at least some credence to it.
It’s quite exciting as new ideas like this don’t come along very often and it’s not common for NASA to simply dedicate significant resources to them in order to see if they pan out. This is what they’re good at though and it makes me incredibly happy to see NASA engaging in some good old fashioned envelope pushing. It might be a while before this bears fruit but the potential for unlocking our solar system is just too good to pass up.
I’ve been unfortunately slack with space based posts on my blog recently and whilst that’s mostly due to my attention being diverted away to other exploits I found it hard to find news or topics that I hadn’t already covered that I thought everyone would enjoy hearing about. Sure when it comes to space even the most hum-drum activities are still amazing feats are deserving of our attention but that doesn’t necessarily spark the creative muse inside me that’s responsible for me churning out a blog post every weekday. Thankfully however my favorite private aeronautics company SpaceX was determined to make waves today, and boy did they ever.
It all started with a single tweet last week where SpaceX teased that “Something big is coming” and released an accompanying 32 second video showing some of their previous accomplishments. Since their bread and butter is full launch systems many people speculated that this would be the announcement of a new rocket class, something bigger than that of the Falcon 9. Today saw the full announcement from Space that the “something big” was indeed their new rocket the Falcon Heavy and it’s set to disrupt the private space industry:
Falcon Heavy, the world’s most powerful rocket, represents SpaceX’s entry into the heavy lift launch vehicle category. With the ability to carry satellites or interplanetary spacecraft weighing over 53 metric tons (117,000 lb) to Low Earth Orbit (LEO), Falcon Heavy can lift nearly twice the payload of the next closest vehicle, the US Space Shuttle, and more than twice the payload of the Delta IV Heavy.
Falcon Heavy’s first stage will be made up of three nine-engine cores, which are used as the first stage of the SpaceX Falcon 9 launch vehicle. It will be powered by SpaceX’s upgraded Merlin engines currently being tested at the SpaceX rocket development facility in McGregor, Texas. SpaceX has already designed the Falcon 9 first stage to support the additional loads of this configuration, and with common structures and engines for both Falcon 9 and Falcon Heavy, development and operation of the Falcon Heavy will be highly cost-effective.
The numbers that SpaceX are throwing around are quite amazing with the Falcon Heavy being able to lift twice the payload weight of the Space Shuttle whilst costing an order of magnitude less per launch. Their specifications make multiple references to the closest competitor the DELTA IV Heavy which would be its most direct competitor citing that they can deliver twice the payload at a third of the cost. Whilst on paper their claim of double the payload rings true I’m still a bit skeptical on “third of the price” bit since the Falcon Heavy’s price range isn’t too far off the DELTA IV Heavy’s ($80~125 million vs $140~$170 million respectively), but it’s still a significant cost saving none the less.
As with all SpaceX rocket designs they are truly something to marvel at. Whilst I’m always get a bit worried when I see large clusters of engines (the Falcon Heavy has 27 engines total) SpaceX has shown they can get 9 of them to work in synchronization perfectly well in the past so I’m sure they’ll have no trouble scaling it up. What really intrigued me was the cross-feeding fuel system that the Falcon Heavy will employ. In essence it means that during its first stage all of the engines are drawing their fuel from the boosters on the side so that when it comes time for stage separation the core stage booster will still have an almost full tank. Couple this with the extraordinary mass ratio of 30, which is almost double that of the space shuttle, and it’s little wonder that the Falcon Heavy can achieve such extreme payload numbers whilst still boasting a ridiculously cheap price.
What’s truly exciting though is their planned production rate for these new rockets. Once in service SpaceX is planning to launch up to 10 of both the Falcon 9 and Falcon Heavy per year for a total of 20 flights per year. To put this in perspective the DELTA IV Heavy has only had 16 launches during its entire lifetime so for SpaceX to pursue such an aggressive launch schedule means that they think there’s a real demand for getting a whole lot of kit up into space, just not at the current price level. Indeed SpaceX will be the first company ever to offer payload delivery into space at the coveted $1000/lb mark, long held as the peak of conventional rocket technology. With SpaceX pursuing such aggressive economies of scale though it won’t be long before that price begins to come down, and that’s when things start to get interesting.
Whilst the cost of ticket to space is still well outside the reach of the everyman for many decades to come breakthroughs like the ones SpaceX are making a habit of releasing signal the beginning of the real space age for all mankind. The $1000/lb mark puts the cost of putting your average human into orbit at around $200,000 just on weight (probably triple that for a realistic cost) which is scarily close to Virgin Galactic’s initial ticket price for a 5 minute sub-orbital junket. As many aspects of getting people orbit become routine and the research costs are a long forgotten memory there’s really nothing stopping the price from coming down to be within the reach of those who would desire it. Sure we’re a long way off from seeing the kind of competition we see with the airlines today but the similarities between the early days of flight and the fledgling space industry are just too strong to ignore. The next decade will bring us some truly exceptional revolutions in technology and all of them will help to make the dream of a true space age for humanity come to fruition.
I really can’t express just how excited this makes me.
Solar sails are one of those things that a lot of people have heard about but no one really seems to know too much about. I guess I owe George Lucas and James Cameron a debt of gratitude for this phenomenon as both their sci-fi block busters feature the technology in one way or another. Still for all the postulating that has been done in the world of sci-fi that appears to well grounded in real world science you’d be hard pressed to actually find any actual craft that have launched and demonstrated the feasibility of solar sail technology. It would seem that something akin to the Mars Curse plagues the potentially revolutionary space propulsion that is solar sails.
That’s not for lack of trying however and since the idea was first thought of way 1924 by Friedrich Zander there have been many attempts to prove that the concept works. For a solar sail to work it needs a large surface area to capture as much of the minute pressure that the sun exerts on everything around it. This poses a significant challenge to craft designers as anything large either means lots of mass or some kind of tricky deployment system. As with any space mission weight is at a premium so all solar sails to date have been extremely large and very thin (in the order of millionths of a meter) and therefore have some kind of complicated deployment mechanism. As anyone who has worked with aluminium foil (which by comparison is 0.2mm thick, almost 100,000 thicker ) before can attest such materials are inherently fragile and all successful solar sail missions so far have focused on actually getting themselves deployed, not on whether or not solar sails actually work.
That might seem a bit strange, especially considering the potential game changer that solar sails are, but it all comes down to its potential applications. Right now there’s really little commercial interest outside Low Earth Orbit and as such the only interest comes from potential scienctifical applications. With the technology as of yet still unproven solar sails won’t make it aboard any deep space missions just yet as there can be no guarantee that it will function as predicted. This hasn’t stopped people from looking into the technology though, with Japan being the latest nation to step up to the plate:
Though solar sail-powered crafts have been used before, Ikaros is the first to attempt to enter deep space. The craft’s 46-foot sails come equipped with solar cells thinner than a human hair. When solar particles hit the cells, they generate power for Ikaros. Mission controllers on the ground will steer the craft by adjusting the sails’ angles, ensuring optimal amounts of radiation are reaching the solar cells.
Ikaros’s pricetag is in the realm of $16 million dollars. And while it’s certainly an ambitious project, there are no guarantees the fuel-free space explorer will work. A rocket will transport Ikaros to space on May 18th, along with Japan’s first satellite to Venus. Stay tuned to see how Ikaros fares when the spacecraft finally gets its day in the sun.
IKAROS (ha! Science humour) is quite interesting for a number reasons. The first is that it is the first solar sail mission to be aimed squarely at deep space. It’s admirable because nearly every other mission thus far hasn’t given any thought to get past LEO or HEO, mostly because it would be easier and cheaper. Secondly they’ve taken the novel approach of converting sections of the sail into solar panels as well, which will provide a decent amount of juice for the craft. This further reduces the required weight of the craft (eliminating heavy batteries) which means they can cram a whole lot more science into this package. Secondly the entire project is being funded on what is to be considered a shoestring, a mere $16 million dollars. If this project is successful it will not only prove that solar sails are a viable propulsion method it will also show that they can be extremely cheap. There are countless deep space missions that could be achieved if such deep space propulsion was this cheap, so you can see why the space community is a buzz with excitement at this missions prospects.
Solar sails are one of those technologies that’s been firmly rooted in the world of sci-fi for decades and the prospect of them becoming real just gets me all kinds of excited. I feel that we’re all extremely fortunate to be on the cusp on the next revolution in human’s ability to travel to places we’ve never gone before. The day will come when humanity begins stretching our reach beyond our solar system and there would be nothing more amazing than to do that by sailing on the solar pressure waves of our very own star.