LEO is the most expensive part, but we know how to do it pretty well at this point. Landing something big enough to carry humans on Mars, on the other hand, is a problem we haven't solved yet.
Landing won't be the hardest part - any Earth-rated capsule with rockets like the human-rated Dragon can do the last leg provided you are leaving Martian orbit with some rocket to slow you down. You may need parachutes to slow the craft to the point the rockets can make their part. Curiosity was complicated because they didn't want to touchdown on rockets.
Now, accelerating a Mir-sized craft towards Mars and decelerating it to orbit while keeping the crew alive for a year outside the Earth's benevolent magnetic field and having enough fuel to accelerate back to Earth (even assuming we'll throw out the interplanetary craft and get to Earth on a capsule) is quite an impressive engineering feat. I'm inclined to suggest that, instead of building a vehicle like that we build one or more cyclers that will orbit the Earth-Mars-Sun system periodically and astronauts would only need to reach them in order to get back and forth. This way we pack all shielding for the long-duration trip into the cyclers and astronauts only need to carry the consumables they'll use. Since reaching them would be time-critical (they won't stop), I would suggest building a similar one that could be stationed in Martian orbit to serve as a fallback plan in case a crew misses the one cycler and has to wait a couple months for the next bus home. These two spacecraft are, essentially, space stations with clever orbits we could maintain with regular resupply missions just as we do with the ISS, but we'd need beefier rockets because the delta-v is the same as a craft going to Mars (because that's what it's doing). Luckily, we'd only need to accelerate the resupply craft - living space is "free" after the first burn.
I am uncertain if these craft are more or less complicated than building and landing the Mars ascent vehicle (much worse than landing a crew capsule, for sure). This sounds very complicated to me.
> accelerating a Mir-sized craft towards Mars and decelerating it to orbit while keeping the crew alive ... and having enough fuel to accelerate back to Earth ...
You don't need to ship enough fuel to return to Earth in the same trip as a manned crew.
You can send orbital depots for return fuel and ascent\descent vehicles ahead of time in unmanned missions. This could be done multiple years in advance.
When you are launching the crew and interplanetary habitat, you only need to bring enough fuel for a one way trip.
It's true, and a clever approach. Since the orbiting propellant depots on Mars would have gotten there with engines, the simplest approach would be to dock the Mars departure vehicle (which could just be the service module of the Mars ascent vehicle) and dock it to the propellant depot and use it as a propulsion stage to match the trajectory of the next cycler passing by. Docking that vehicle with the cycler would allow any extra fuel to be used for trajectory corrections. As long as the mass you are adding to the cycler has propellant and an engine, there is no big issue with adding it.
LEO by far isn't the most difficult part, not if you are aiming for moon/inter-planetary transport.
LEO is ridiculously easy to get too, The ISS is at 340KM, GEO orbit is 35,000 you can put payload in LEO with "amateur" rockets, GEO/HEO is a completely different story, it's extremely hard and you need a heck of a rocket to do it with any substantial payload.
Now from GEO/HEO to anywhere else it's quite easy to get because you are pretty much near the escape velocity so it takes almost no delta-v to get pretty much anywhere you want in the solar system, at least as far as getting to a higher solar orbit goes as the closer you get the faster your solar orbital velocity is so using that speed to get even to the edges of the solar system takes very little energy.
If we talk about say a mars shot then most of the energy in that trip goes to 2 things, getting to high earth orbit, and then slowing down for a mars capture the amount of fuel needed to do the martian orbit transfer is almost negligible.
The concept of LEO being "ridiculously easy to get too" is mad.
No amateur rocket has made orbit or even come close. The difficulty of building a vehicle to make LEO is not comparable to building one to raise altitude once in orbit. LEO to GEO is less than half the delta-v of surface to LEO. It is routinely done by satellites alone. The only reason getting to GEO is particularly hard is because you have to get to LEO first.
https://en.wikipedia.org/wiki/Civilian_Space_eXploration_Tea...
Their "go fast rocket" got to about half the altitude of Sputnik so if you got the cash you don't need to scale "go fast rocket" up by that much to put a cube-sat / micro-satellite up there.
It only takes 2 km/s to get to 100 km altitude on a ballistic hop. But the gravity pulls you down.
It takes a 8 km/s horizontal velocity just to stay in orbit. That is in addition to the 2 km/s to just get to the right altitude.
So just by speed ratios orbit is 5x the difficulty of a space hop. In reality rocket scaling is exponential (you need more fuel to carry more fuel...)
Anyway, I do think nowadays "amateurs" actually could build orbital rockets with budgets in the low millions class. Modern electronics and GPS make it a bit easier than a few decades ago.
The MTCR has 34 members, basically the G20 minus China and India. Since the MTCR doesn't have any provisions for enforcement, (It's "an informal and voluntary partnership") its US equivalent is the International Traffic In Arms Regulations Act. (Category XV, Section c, if you want to read how the US statute words it. In imperial units, of course, just to make things simple.)
Not sure what your math is, but mine is about 20% larger rocket to get to 160KM and have enough speed for orbit, at least as far as cube-sats that can skip on the atmosphere for a bit go.
There's also https://en.wikipedia.org/wiki/Copenhagen_Suborbitals with their plans for a manned suborbital flight, their rocket (although it blew up) could also be used as a base for amateur orbital flights.
I'm not entirely sure what is so surprising here, it's a question of money at this point, but amateur rockets are quick close to being able to reach space, this doesn't mean that they will be commercial viable or even viable for any non-anecdotal use.
What's surprising is that amateur rockets can reach space on suborbital trajectories but none of them come even remotely close to orbit.
Altitude is the easy part, relatively speaking. Getting the speed for LEO is the hard part. The GoFast rocket you linked to has demonstrated up to 4,200MPH. Low earth orbit requires about 17,000MPH.
That factor of ~4 requires massively larger rockets, because the rocket equation is cruel. Each incremental increase in final speed requires an exponential (actually using this word correctly, for once) increase in the amount of fuel. Fuel in return requires more hardware like tanks and engines, which means yet more fuel is required, etc.
Edit: using RP-1 as the fuel in a single stage, getting to 4,200MPH requires that 45% of your total rocket mass be fuel at launch. Getting to LEO requires 94% of the mass to be fuel.
Yes I understand it quite well, ~20% scale up which is 20% longer, and 20% wider is quite a big change in mass.
The big problem is either staging or being able to shift it to a shallow enough trajectory and get enough velocity, but it might be solvable if you can do a zoom climb type launch from an aircraft similar to how Pegasus/SpaceShip One do it.
https://en.wikipedia.org/wiki/Pegasus_(rocket)
How is a 20% scale up going to get you anywhere close to the extra dv needed? 20% on each dimension is still only 70% more rocket, where you need something more like 10x more rocket to make that leap.
That's 1.2^3, or 70% more... not even close. Also remember that making the rocket bigger also increases the dry mass, which further increases the fuel requirements.
The difference in ISP between a liquid-fueled rocket (say 450s for LH2/LO2, 350s for RP1/LO2) and solid propellant (250s) makes a huge difference to your prop fraction. To get, say 8km/s delta-v, just plug it into the rocket equation:
Standing on the surface of the Earth your potential energy relative to infinity is −62.6 MJ/kg. If you were standing still 160 km up, you've added roughly 1.6 MJ/kg. (You climbed 160,000 meters against a force of 9.8 Newtons per meter.)
To then go into orbit you have to add a sideways velocity of about 7800 m/s. Apply the famous kinetic energy = 0.5mv^2 and going into orbit requires 30.4 MJ/kg of energy. That's 19x more energy than is required to get to altitude!
But it gets worse! If you're going to go into orbit, you need to think about getting down. Going up we go straight up out of the air and then add sideways velocity. Going down we let the atmosphere do most of the work of slowing us down. But in order to survive that you need a much more rugged device with a heavy heat shield. You're now both doing more work per mass lifted AND you're lifting more mass!
But we're not done with the bad news. A fundamental fact about rockets is that you have to lift the fuel you use later in the launch. That means that as you're increasing the final velocity you're getting an ever-decreasing ratio of energy expended to useful kinetic energy for your payload.
Put it all together and actual rocket scientists have told me that it is about 100x easier to get to orbital altitude than it is to actually get into orbit.
That said, LEO is the half-way point. Getting into LEO takes about as much energy as it does to launch from LEO entirely out of Earth's orbit.
A 160km altitude cubesat would require a minimum 7.8km/s of delta-v. Anything less than that and it will burn up in the atmosphere after a few orbits. GoFast Rocket achieved a top speed of 1.6 km/s (3580 mph).
It needs to go 4 times faster, and no, a 20% larger rocket won't cut it. 20000% larger by mass would be more like it. It also needs a 2nd stage burning liquid propellant with high specific impulse which is way, way harder to build than a dumb solid propellant rocket.
Noone (not even governments) has been able to send a single stage rocket to orbit.
Israel and India use 3 stage HTPB solid rockets for space launches you don't need to have a 2nd stage liquid fuel rocket to get to orbit.
Also 20000% larger by mass? want to be a bit more serious? if you scale this rocket by 35-40% you get to about the size of the first stage of the Shavit solid fuel space launcher which is a commercial space launcher.
You do understand how scaling works on 3 dimensional objects right?
Based on my previous conversations with this guy, this seems to be a recurring pattern. I do hope that he's using these conversations to recognize and fill in the holes in his knowledge. :)
What good does it do to scale something up to the size of the first stage of a four stage rocket? Those other three stages are pretty important to that whole putting-stuff-in-orbit business.
Edit: I see Shavit can also launch in a three stage configuration. My overall point remains.
LEO difficulty is mostly speed, not height. SpaceShipOne flew above 100 km - but it's a long way to reach Vostok-1 performance, as delta-V for SS1 is more than four times less than for Vostok-1.
