Architects want to hang a skyscraper off an asteroid. Just how mad an idea is it?

Every so often, a story does the rounds on the internet about an upside down skyscraper in New York that would hang from an asteroid.

Yes, a tower full of apartments suspended in mid-air, attached to a giant space rock floating 31,000 miles up.

Presumably everything inside would be the right way up because, you know, gravity.

Commenting on their design most recently, architects at Clouds AO said: ‘Analemma Tower is a proposal for the world’s tallest building ever. Harnessing the power of planetary design thinking, it taps into the desire for extreme height, seclusion and constant mobility. 

‘If the recent boom in residential towers proves that sales price per square foot rises with floor elevation, then Analemma Tower will command record prices, justifying its high cost of construction.’

‘High cost’ may be a bit of an understatement, but we’ll come back to that later.

Putting aside the impracticalities of living in floating skyscraper only accessible by drone, could the incredible feat of capturing an asteroid and hauling it into Earth’s orbit ever really be done?

Well believe it or not, the idea is ‘not completely impossible’, according to Royal Observatory Greenwich astronomer Dr Greg Brown.

‘As ridiculous as it sounds, this is far from the first time that similar projects have been suggested,’ he says. ‘Their concept is similar to the famous “Space Elevator”, the concept for a literal elevator from the ground to space, thereby making space travel considerably simpler… if you could just somehow build the thing in the first place.

‘It would not be completely impossible to capture an asteroid. Some of the moons in the solar system are likely just that, indicating that nature can do it already.’

Humans, too, have already shown they can change an asteroid’s orbit, even if only by a small amount, thanks to Nasa’s Double Asteroid Redirection Test (Dart).

But scaling up from smashing a rocket into an asteroid to capturing one moving at up to 55,000 mph is a matter not only of technical development, but also investment. As a guide, the Dart mission cost more than £255 million.

‘Moving an asteroid into orbit around the Earth [is] a matter of scale and precision, both of which are probably beyond us right now without absolutely vast investment,’ says Dr Brown.

But while the financial aspect might not have been fully thought through, the designers’ plan to hang something off a captured asteroid has taken into account how a geostationary orbit would function in real life. The skyscraper itself would wander around the world in a figure of eight pattern, ‘travelling between the northern and southern hemispheres on a daily loop’. 

Not ideal if you had a noon meeting in Manhattan and find yourself over Mexico City.

However, even factoring in a bit of asteroid wobble, there is a bigger problem to overcome. Creating a giant butterfly net capable of capturing one of the solar system’s 1.3 million asteroids.

‘As to whether the structure is possible – not yet,’ says Dr Brown. ‘There is no material yet produced by humankind that can take the immense strain associated with such a building. In fact, the cabling involved would not be able to hold its own weight, let alone that of a free-hanging skyscraper.’

Slightly off-topic, but the same is true for a King Kong or Godzilla the same size as they appear in the latest films.

‘For now, at least, this design is a cool concept but well beyond the ability of the engineers of the modern day,’ says Dr Brown.

But not to put a total dampener on the idea of using asteroids for humanity’s gain, he adds there are other potential opportunities – including intergalactic travel.

‘The most commonly anticipated use for asteroids is asteroid mining,’ says Dr Brown. ‘As chunks of the leftover material from the formation of the solar system, they are rich in materials that on Earth are relatively rare or buried deep underground. The ethics behind such projects are complex and the idea remains controversial, but certainly it is an idea that individuals are likely to consider in decades to come.

‘As for using them for travel from one place to another, it isn’t impossible but the practicality may again be the biggest issue. Instead of thinking of them as the ship itself, it might be more reasonable to think of them as having a ship latched onto them so that the asteroid can be used for raw materials for the creation of spare parts. 

‘As for whether we’ll be doing it any time soon, again it seems unlikely. We have a decent track record of travelling within our solar system without the use of a rocky companion to get us there.

‘But with a couple of recent detections of interstellar asteroids, like Oumuamua, hitching a ride out into the wider galaxy on one might not be so ridiculous.’

And perhaps a more pressing matter might be dealing with asteroid Bennu. Nasa recently visited the 500m-wide, 78 billion kg asteroid, bringing home samples as part of it’s OSIRIS-REx mission, but in 150 years or so the asteroid could be heading our way, with a 1 in 2,700 chance of colliding with Earth on Tuesday, September 24, 2182.

Exact time TBC.