The exploration of space is all dependent on the speed of light being a maximum value. It may be possible to warp space, but we don’t have a black hole close by to do it effectively, two colliding only giving a minute ripple in space, and the various LIGO’s not detecting any other space warping that would signify such a transport type signature. The LHC at CERN operates at 6.5 TeV per proton and it hasn’t even detected any warping whatsoever, so things don’t look promising.

Unless there is a back door into physics that nobody has come across in our history that will allow you to side step time it’s unlikely that a trip to even the nearest star would take less than 8 years. An asteroid hollowed out, say a minimum 3 miles across with it’s own self-contained community and next to no entropy from its system integration, powered by solar collectors around earth may stand a chance. But that’s also dependent on a few other factors that haven’t been created yet. It would still probably have to lose probably somewhere near three quarters of its mass in getting there and loading up with the same to return.  as we are still in nearly every case dependent on shoving things out the back as fast as possible.

Mars like the Moon is little more than a barren rock in space. There is no nature, culture, population, and so little atmosphere that you will die within seconds without a spacesuit. The romantic notion of a beautiful planet like earth is really like the difference between an alive animal and a fossil. It’s nothing you can experience except behind a thick piece of plastic or glass, and the reality of finding a burger packet there is probably at a cost of £20,000 to get it there, so discarding things like that is pretty dumb and a waste of scarce resources, probably being the only cardboard within 34 million miles.

Things were left on the Moon as it would cost millions of pounds to bring even some of the smallest things back. With Apollo 11, costing $355 million, the most they could bring back from the Moon was themselves and 48lbs of moon rock, about $500,000 per pound and Mars is at least ten times as expensive.

There’s a lot of difference between imagination and reality. Stainless steel isn’t too good for a spacecraft as it’s so heavy. Stainless steel is about 2.5 times denser than aluminium and nearly twice that of titanium. Most rockets and craft are made of composite materials to keep the weight down. Take the Apollo mission. Saturn V rocket, total weight 3000 tonnes of which 2/3rds is fuel. This will put a 30 tonne Command and service module, design life 11 days combined, plus a 15 tonne lunar module, design life 3.5 days on a path to the moon.  You get there and back, and a Command capsule, design life of about 12 days, weighing 12 tonnes to be returned, about 4%. So effectively you used 2000 tonnes of fuel to get 12 tonnes there and back again. If the return spacecraft was twice as heavy you would not need 4000 tonnes, but an extra 1000 tonnes for lifting the extra fuel off, and an extra 400 tonnes fuel for that fuel and 100 tonnes for that fuel and 25 tonnes for that fuel. So far people have been surprised by Musk getting the Falcon Heavy to work, but the upgrade in scale from low earth orbit is the difference between a bicycle and Ford Mondeo. Possible if you acquired existing experts already in the field, but so much continuity has disappeared.