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SpaceX Shows Off Its Interplanetary Transport System in New Video (techcrunch.com)
Elon Musk's SpaceX plans to send humans to Mars with a ship called the Interplanetary Transport System, the company announced today in a video, revealing how the ITS will actually work. The ITS will be capable of carrying up to 100 tons of cargo -- people and supplies -- and it will utilize a slew of different power sources en route to Mars. From a report on TechCrunch: SpaceX has released a new video showing a CG concept of its Interplanetary Transport System, the rocket and spacecraft combo it plans to use to colonize Mars. The video depicts a reusable rocket that can get the interplanetary spacecraft beyond Earth's orbit, and a craft that uses solar sails to coast on its way to a Mars entry. The booster returns to Earth after separating from the shuttlecraft to pick up a booster tank full of fuel, which it then returns to orbit to fuel up the waiting spaceship. The booster craft then also returns to Earth under its own power, presumably also for re-use. The solar arrays that the spacecraft employs provide 200 kW of power, according to captions in the video.The Verge is live blogging SpaceX's conference, and has details on specs.
That's some incredibly sophisticated vapor. Amazing!
They show the spaceship being launched first, to be refueled by a drone tanker. Shouldn't the tanker be launched first? Unlike the spaceship, it can wait indefinitely in orbit if the second launch is delayed.
NASA figured that out a long time ago.
The Mayflower's tonnage was around 180 tons. Tonnage is how water a ship displaces. The actual storage capacity is unknown but would have been a small amount of that.
No, a ships displacement is measured in tons but the 180 tons of storage is just that. The estimate of Mayflower's displacement is somewhere in the neighborhood of 250 tons and total weight about 400 tons including some 130 tons of ballast. Of course all these are approximations based on the given dimensions of the ship and what was typical for the period.
Yeah, but the Pilgrims had to haul a lot of Bibles since the unknown wilderness they were shipped off too had Satan hiding behind every tree.
There's no trees on Mars.
Heavy lift for the Saturn V was: ~90,000 lbs of end-payload, for a trip to the moon. This new thing is 200,000 lbs or payload, so more than twice the heavy lift capacity of the biggest rocket the U.S. ever made, unless they break it up into smaller component launches. I want to be there when that rocket launches, albeit at a safe distance! https://en.wikipedia.org/wiki/...
And that's different from NASA/Energia how?
Space ex has a failure rate 10 times worse. The FAA needs to step in and force them to take safety seriously.
Failing, as it turns out, is an effective way of trying new things and finding out what works. Painful, but very very effective.
The best thing about SpaceX is that they aren't afraid of failure.
The worst thing that could happen would be if the FAA steps in and no longer allows companies to fail. If you aren't allowed to fail, you're not allowed to innovate. The only way to take the chance of doing new things is by taking the risk of failure.
Or, to use a quote: “Only those who dare to fail greatly can ever achieve greatly.”
http://www.geoffreylandis.com
While Mars is not exactly friendly, living off the land there is actually possible. This is why people even think about colonizing it. It has water, it has sun, it has CO2. Grow plants there and so on.
But of course no one is going to colonize it with a single 100 ton ship. The idea is to send a lot of them. 10,000 was the number Musk quoted, to get to a self-sustaining industrial civilization.
entropy happens
For example, the Saturn V used two different kinds of fuel: LOX with RP-1 and liquid hydrogen. This optimized performance for the 1st stage booster vs the upper stages. This increased the cost and complexity of the ground support. SpaceX uses only one kind of fuel for all stages. This reduces complexity and cost.
If you build a booster stage that is robust enough to return with only aerobreaking, it is going to weigh more and be more complex. You pay for that extra weight for every launch. Note that some of the structure is only used for re-entry and is dead weight on the way up. Breaking with the engines means they are used both on the way up and the way down.
As Musk points out in his presentation, fuel is the cheapest component of the launch system. Therefor it makes economic sense to use more fuel to land the launch stages, which are the expensive components.
The people at SpaceX are not dumb. They came up with a different solution because they framed the problem differently. Rockets are hard, and there is not a single best way to build them. There are a lot of projects that use vertical powered landing: McDonald-Douglas DC-X and Blue Origin New Shepard are examples and NASA funded various prototypes. Aerobreaking is not the only reasonable option.
Why is Snark Required?
They say it can transport about 100 tons. That's not much for a colonization effort. The Mayflower that transported the pilgrims to America was rated at about 180 tons. They could expect to live off the land for the most part whereas whoever takes the trip to Mars will be entirely dependent on what they bring with them. Without help from the natives it's likely that the Mayflower's people would not have done as well if they managed to survive at all. Maybe the Martians will help Musk's colonists.
Well, just like when Musk launched the Autopilot saying this is going to become our self-driving car he's exaggerating quite a bit what it'll do in the short term. It'll be an outpost, sustained by Earth resupplies and the bigger the outpost, the greater the need for resupplies. It'll be a very long time before you hit critical mass where each expansion would make it more self-reliant. It'll mostly be a proof of concept, can we expand the living quarters with on-site materials or do we need domes from earth? Can we generate enough food, water, air, heating and power and so on? The burden on Earth needs to go down, then the size of the outpost can go up.
I expect they'll keep enough emergency supplies and consumables in reserve to survive while they try things out and figure out what works and doesn't. But if it doesn't work, we have to send more supplies and less people or all supplies and no people or in worst case just abandon it. Though I don't really believe that, I mean if they just sit in a bunker and eat canned food like on the ISS it's hard to see any reason why they should be forced to leave. But they also wouldn't really be making any progress towards colonization that way, it'd be just survival. Then again, surviving Mars might in itself be the first step since we haven't actually done that yet either.
Live today, because you never know what tomorrow brings
Parachutes are shit for precision landing. But the reason they can get away with using mostly rocket power to land is that the first stage is mostly empty by that time, and rather light. So a little bit of firing is enough to brake it completely, requiring little fuel. In fact, the first stage is so light that they only use one of the nine engines to propulsively land it.
entropy happens
Sure. But it will do so over the course of many thousands to millions of years, allowing plenty of time for "booster shots" of atmosphere. If we can create it in the first place, maintenance is probably a much easier task.
Even among naturally preserved atmospheres, there are other techniques for generating a magnetosphere should we decide to create one. Venus for example has no magnetic core, and is subjected to a *much* stronger solar wind, yet manages to hold on to it's atmosphere thanks to an induced magnetosphere generated within its ionosphere. Whether a similar process could be induced on Mars, I don't know, but it's proof that there's more than one way to generate a magnetosphere.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
if you rely on your rocket engines entirely to decelerate (as the video clearly shows), you would need roughly double the fuel
No, it can be done with much less than double the fuel. The trick is that the boost-back and landing burns take place after the second stage and payload have separated from the booster. Thus, because the booster is much lighter on the way down than it was on the way up, it can decelerate itself with relatively little fuel. (On a two-stage rocket, the empty first stage typically weighs significantly less than the fully-fuelled second stage and payload.)
SpaceX has already demonstrated this experimentally with the Falcon 9: the payload penalty to orbit for reusing the first stage is only about 30%.
rely on parachutes and air resistance
The ITS surely takes advantage of air resistance to some extent. Having said that, while aerodynamic drag is an excellent way to decelerate small things, it becomes progressively less effective for larger objects due to the fascinating square-cube law.
Air resistance scales linearly with the object's surface area, while the required deceleration force scales linearly with the object's mass. Surface area scales as the square of the object's linear dimension, while mass scales as the cube of the object's linear dimension. Thus, the mass grows faster than the air resistance.
This is why an ant or a cockroach will land completely unharmed even if dropped from the top of the tallest building in the world, whereas a much larger human would die instantly on impact. It's also why small meteorites tend to burn up very high in the atmosphere, whereas large ones may retain enough speed and mass all the way to the ground to make a crater.
yep, all the fire on the bottom of the shuttle, or a mercury capsule means that air resistance is actually slowing the spacecraft down
The ITS first stage dwarfs the Mercury capsules. Even so, the Mercury capsules had to land in the ocean because their parachutes couldn't slow them down enough to land softly on land. That's very bad for reusability, because sea water is corrosive.
The Space Shuttle Orbiter is much closer in size, but still only massed maybe 1/3rd as much. While it was able to slow itself via aerodynamic forces alone, giving that capability to such a large vessel was extremely expensive in a variety of ways. I won't side-track this post with a full explanation right now, but suffice it to say that the decision to make the Orbiter a giant winged vehicle was a major contributor to all fourteen crew deaths, and to the massive cost overruns.
(There is a reason that neither NASA nor anyone else wants to build a new Space Shuttle - it was a failed design. Dream Chaser may look superficially similar, but it is much smaller and thereby avoids many problems.)
For the ITS, specifically, a winged setup would have the additional problem that it could not return the booster directly to the launch site. Instead it would have to land on an extremely large runway somewhere down-range. Both the launch site and the landing site would need to be on the coast, since the booster is far too big to travel any other way, than by ship.
And yes, I learned this playing Kerbal Space Program
Kerbal Space Program is great. You have to really work at it to accurately model a system like this though - you need to use all the realism mods, build the system at full size, and use a competent auto-pilot for the landing burn. (Manual landings are difficult and waste a lot of fuel compared to a computerized "suicide burn".)
Do it right, and you'll find that Elon's scheme actually works pretty well.