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In my Sci-Fi universe, I want humans to, initially, have two traits to their spaceship building:

  1. Really good drive systems, at least compared to other races.
  2. Complete and utter lack of any sci-fi "Deflectors"

From everything I know, this leads to a ship needing a heavily armored prow to withstand any sort of extended mission. Any sort of satellite debris hitting the ship when entering orbit needs to be absorbed and/or deflected, and the occasional errant object in interplanetary travel needs to be able to be withstood as well. And that's before we even get to military ships.

The question I have is What is required for a "High-speed" spacecraft without shields? What is a reasonable "Speed Limit" for such vessels, keeping potential damage to a minimum? Being able to withstand impacts is great, but if you have to replace and repair the front of your ship after every trip, it's not really that useful (Although a courier vessel could take advantage of such a scheme).

To be entirely clear, I do not want alternate deflectors, or EM fields, or whatever. These ships operate like a celestial snowplow - If it's in front of them, it gets run over.

Additionally, the ships are not "Torch Drive" ships that are continually thrusting. They accelerate up to travel speed, coast towards their destination, and then slow down on arrival. I expect trips to take weeks or months. High Fractional-C velocities are, frankly, unwanted. At even 5-10% of light speed, the energies involved are enormous.

This is also for sub-light travel, not faster-than-light. FTL is accomplished in a completely different method, where such things are not something that needs to be worried about. Generally speaking, this is for travel within a system.

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    $\begingroup$ I am puzzled. "Fractional-C velocities are, frankly, unwanted." Unless these spaceships travel faster-than-lightspeed, then on every trip their velocities will will be fractions of c. Otherwise they can only to the planets of the solar system, more likely Mars or Venus, because they're the only planets that can be reached in weeks or months without using torchships (though this depends on the length of the acceleration phase). Or have I completely misunderstood your question? $\endgroup$ – a4android Jul 30 '17 at 8:51
  • $\begingroup$ There is a lot of useful information here: en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) $\endgroup$ – user9981 Jul 30 '17 at 14:54
  • $\begingroup$ @a4android I'll clarify in the question, but I was more referring to high-fractional-C velocities. Going even 10% of lightspeed means even the smallest object will impact with a lot of mass. $\endgroup$ – Andon Jul 30 '17 at 17:23
  • $\begingroup$ Thank you for the clarification. The form of words was somewhat paradoxical, not that I don't enjoy a good paradox, but fixing it makes the question better. $\endgroup$ – a4android Jul 31 '17 at 2:46
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Since you mention other races (species), your ships will be probably be travelling between solar systems. Assuming that these solar systems are at least light years apart, your desire for week/month trip lengths implies that you want FTL travel.

So you want a method for FTL travel which can operate without shields?

Have your ships traverse most of each journey's distance in an alternate dimension where matter is not encouraged to exist.

Start each journey by flying up from the planet's surface to a maximum non-orbital height; a height where the atmosphere is just thick enough to slow down would-be orbital objects and cause them to plummet downward. From the safe zone, use your ship's scanners and computers to plot a debris-free course up out of the planet's gravity well. When the window opens for that course, rocket your ship upward to the comparative safety of interplanetary space.

Once there, open a dimensional doorway and slip your ship into the non-material dimension. This alternative dimension does not actually forbid matter, it just doesn't have any of its own. Your ship does not dissolve upon entry. It is just alone in an infinite empty space. Another unusual attribute of this other dimension is that it does not enforce the light speed barrier, so your ship can travel as fast as your scientists can figure out how to go.

Within this empty space, you can use your super-fast human-made drives to move your ship to a location within the emptiness which is equivalent to a point just outside the gravity well of your destination planet. There, you simply open another dimensional doorway and slip back into our matter friendly realm.

Landing simply requires a reversal of the steps taken during lift off. Find a debris-free course from the gravity well's edge to the new planet's maximum non-orbital altitude, rocket in and then fly down from there.

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  • $\begingroup$ FTL is accomplished in a completely different manner. This is for slower-than-light travel within system. I'll clarify the question. $\endgroup$ – Andon Jul 30 '17 at 17:21
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Shape the ship! Make it like a needle, with a very long (mile long) prow. Various materials are harder than diamond (See Here), I would suggest something like #1, carbyne, at 200 times the strength of steel and much harder than diamond.

This shape won't deflect anything much bigger than your ship, of course: But you should be able to see those large objects, things larger than your ship, in plenty of time to change course. You probably also don't want to run into anything more massive than about 5% of your ship's mass.

Your prow can be a combination of shock absorber and physical deflector that comes to a "sharp" point (relatively speaking; perhaps a dome a few feet wide), it is a cone ramping to wider than the width of your ship. It clears the way of any small debris, like satellite size or big rock size; such debris tumbles down the spear point and past your ship.

This is to keep you from running into things small enough that you cannot see them in time to change course. Your sensors, of course, will be mounted near the tip of this prow. Since you are traveling at sub-light speed, there should be plenty of time for you to see very large things and avoid them.

One more feature you can add is that this prow is not even attached to your ship; it is an independent path-clearing piece of equipment that you launch and then follow behind. In the event it does ram into something large and stops; your follow distance can be many miles (even a thousand miles), far enough that the cleared space cannot be filled with anything damaging after the cone passes, but long enough that, should the cone hit something big, your ship has plenty of time to react and not crash into the mess created; by stopping or veering off for safety. Given the hardness of the cone (which you can increase by sci-fi hand-waving), chances are it shattered or penetrated into anything it did hit; which should be very rare. But for safety, let it do its work separated from the ship itself.

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/ Being able to withstand impacts is great, but if you have to replace and repair the front of your ship after every trip, it's not really that useful/

No, that is exactly what you do. With whatever junk you can find, scavenge or steal. The Improvised Armor trope is an awesome one!

http://tvtropes.org/pmwiki/pmwiki.php/Main/ImprovisedArmour

The term "Hillbilly Armor" is from the Iraq war when soldiers were Mad Maxing up their poorly armored vehicles with whatever they could scrounge up. But soldiers have been doing that a long time. enter image description here https://www.pinterest.com/pin/496873771361431089/

If it gets too bunged up, detach it and find more. Or find some new stuff and stick it on in front. In space you do not need to worry about aerodynamics. Something from the planet surface. Someone else's ship that they left unattended. A wad of comet, steaming off ice and methane in your wake. Some hunk of stuff you found in space. A random asteroid that happened by.

Depicted: the Endurance from Seveneves by Neil Stephenson. enter image description here

https://www.quora.com/What-science-fiction-media-features-realistic-spacecraft

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  • $\begingroup$ Ad-hoc armor is great for military vessels or, say, a scavenger fleet. However, a shipping company isn't going to buy a ship if they have to then immediately modify it to be capable of doing it's job. They'd insist that it be designed up to spec. That's what I'm going for here. $\endgroup$ – Andon Jul 30 '17 at 17:30
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    $\begingroup$ Put the cargo in front then. Sand, coal, ore and durable stuff in front. A few impacts will not depreciate that. If the foremost container is so riddled with holes it will not hold ore, fill it with ice and rocks. Fine china goes in back. $\endgroup$ – Willk Jul 30 '17 at 18:11
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    $\begingroup$ @Andon I wouldn't consider this to be "modification". It's just topping off expendable the supply of expendable components, a regular maintenance requirement according to the design spec, no different from filling the fuel tank or oiling door hinges. $\endgroup$ – Logan R. Kearsley Jul 30 '17 at 18:32
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Based on the description, you are looking at an STL system. Although the common sense answer is to simply coat the ships hull with metres of ice to absorb the radiation and impacts of interstellar dust and gas molecules, you clearly are looking for a different answer.

The answer is actually two fold. Make the ships light sails, and use the drive beam to clear a path for the ship to go through. There are several possible approaches, but essentially using an immense laser or perhaps an immense mirror to focus the light from the home star, you can put a huge amount of energy on the sail. Shining the beam into space years ahead of time can ionize the gas and push interstellar dust out of the way, creating a clear path for the ship to follow through.

One potential method is Jordin Kare's "Sailbeam" concept, using the momentum of tiny sails accelerated to immense velocity to drive the spacecraft.

enter image description here

Sailbeam concept

More speculative is the suggestion that "Tabby's Star" has a mirror two light seconds in diameter, which can direct the light from the star to push huge lightsails, even ones towing interstellar arcs. The mirror could theoretically focus the beam 1700 light years away to vapourize the Earth, so being good neighbours is always a good plan.

enter image description here

The building permit took a long time to arrange

So the essential thing is to use the energy of the beam to clear the way so the spacecraft can dispense with the armour or shielding needed for interstellar travel.

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Just declare that your system of travelling faster than light has the properties that you want. You need FTL travel for the universe you want, there's no really scientifically respectable way of achieving it based on what we currently know, and so you can have your ships sideslip into another universe where there's no debris and no light speed limit, or whatever else you want.

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  • $\begingroup$ This is for slower-than light travel. $\endgroup$ – Andon Jul 30 '17 at 16:52
  • $\begingroup$ @Andon Not with aliens and trips taking weeks or months, it isn't. If you want aliens and slower-than-light travel, your trips will take years at best, and often decades, centuries or even millennia. If you really want your trips to take months at the longest, you're confined to our solar system. $\endgroup$ – Mike Scott Jul 30 '17 at 17:21
  • $\begingroup$ Oh, it absolutely is. FTL is accomplished in a completely different manner. This is for interplanetary travel within a system. $\endgroup$ – Andon Jul 30 '17 at 17:27
  • $\begingroup$ In that case, it's even easier. Just give your humans a top speed of 0.001c in normal space, and everyone else a top speed of 0.0005 c. That's not fast enough to worry about debris, but easily fast enough to get round a solar system in months. $\endgroup$ – Mike Scott Jul 30 '17 at 17:30
  • $\begingroup$ Ah, but even at normal orbital velocities, things can get dangerous. Take, for example, this test by the ESA $\endgroup$ – Andon Jul 30 '17 at 17:32
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This was asked many months ago, but I just saw it while googling something related, and thought I would add in my own two cents:

The way I see it, you can try to brute force your way through stellar debris, or you can minimize how much those impacts matter.

Most of the impacts will be relatively small. Design your ship to simply allow them to pass all the way through and then patch the holes. Self-sealing tech would work here well. In some universes, like BattleTech, they have substances that are used especially for this sort of breach. BattleTech calls their substance HarJet if you want to read up on that. You can also have a shell of liquid around your ship, between the inner and outer hulls, this would help absorb impacts and prevent hard structures from getting shattered by the sudden jolt on the ship.

In this case you would want two features for your internal systems. The first would be massive redundancy. If an impact punched through something, you would want back up systems to come online, and back-ups for the back-ups. You would also want automated repair systems, robots that can handle repairs in damaged sections, or even remote drones.

Personally, I would have the outer hull have a water shell just inside it, and have a water shell around every vital component's area, and inside the habitable areas. In fact I would have the spaces inside bulkheads across the ship filled with water as well. This would serve to seriously bleed off kinetic energy as whatever piece of space dust that is hitting your transfers a ton of it into each water pocket it encounters.

All of that water would also have additional utility in being able to help maintain hydroponics, and being able to be converted easily into hydrogen fuel.

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Most of the shielding in place on existing spacecraft isn't to protect against space debris, which is extremely rare.

Shielding is in place is to protect the astronauts against various forms of solar radiation, which can kill the occupants. On earth, the layers of atmosphere, plus the earth's magnetic field, plus the Van Allen radiation belts, stop that radiation before it gets to the surface. The primary reason earth has a thick atmosphere while Mars has very little is, Mars doesn't have a strong magnetic core that deflects the solar wind.

We on earth are living near a giant, unshielded fusion reactor. Once outside of the protective layers around earth, you'll get the full blast.

So, unless you will have your travelers always wearing anti-radiation suits, which will limit their mobility, you will need some form of radiation shielding, or they won't be able to approach any solar systems... which presumably would be the purpose of their travel.

Keep in mind when thinking of armor plating to deflect or withstand meteor collisions that the spacecraft will decelerate when hit, while the occupants won't... until they slam into the interior of the spacecraft. Newton's law, and all of that. Even with armor plating, a collision with a large enough meteor could prove fatal to the travelers.

Better to put on some form of detection system to identify and avoid larger meteors. That, plus the maneuvering fuel, would still weigh a lot less than armor plating. Maybe a directed energy weapon to break up smaller meteors that threaten the spacecraft.

In any case, the chance of encountering a free traveling meteor is quite rare. Most have been captured by the gravitational fields of suns or planets.

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