# Best shape for space ships? **URL:** \ **Category:** Factual Questions\ **Created:** [August 12, 2012, 9:08am UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257 "2012-08-12T09:08:10Z")\ **Posts on this page:** 8\ **Page:** 3
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [August 17, 2012, 11:08pm UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257/41 "2012-08-17T23:08:53Z")
> [@Dr.Strangelove](#): > > The ISV Venture Star–the interstellar ship in _Avatar_–is one of the more plausible interstellar ship designs, and the radiator fins (glowing red) are a prominent part of the design. I love the Venture Star; but with the deceleration motors at the rear pointing forward, everything else is exposed to the drive; this could be a problem unless the ship materials are very resistant to radiation. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [August 17, 2012, 11:44pm UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257/42 "2012-08-17T23:44:28Z")
> [@eburacum45](#): > > I love the Venture Star; but with the deceleration motors at the rear pointing forward, everything else is exposed to the drive; this could be a problem unless the ship materials are very resistant to radiation. It’s all speculative of course, but I’m not sure that a problem. The exhaust is going to be a very thin stream–even though it’s a gas (or plasma), it is moving so quickly (a large fraction of the speed of light) that it wouldn’t have time to expand and impact the crew module. The propellant is hydrogen, so the exhaust itself shouldn’t be radioactive. The dangerous parts are the engines themselves, since they mediate a matter/antimatter reaction. Lots of gamma rays from that, so the engines are as far away from the crew modules as possible. The dragger configuration makes sense since it’s easier to build lightweight tensile structures than compressive ones. ---
**Author:** ![Lust4Life](https://avatars.discourse-cdn.com/v4/letter/l/ecc23a/32.png) [@Lust4Life](https://boards.straightdope.com/u/Lust4Life)\ **Post date:** [August 18, 2012, 4:10pm UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257/43 "2012-08-18T16:10:23Z")
For vessels travelling outwards using the Solar Wind either as their primary motive force, or as an add on to their engines a huge sail would be in order. ---
**Author:** ![md2000](https://avatars.discourse-cdn.com/v4/letter/m/73ab20/32.png) [@md2000](https://boards.straightdope.com/u/md2000)\ **Post date:** [August 18, 2012, 4:43pm UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257/44 "2012-08-18T16:43:46Z")
> [@eburacum45](#): > > I love the Venture Star; but with the deceleration motors at the rear pointing forward, everything else is exposed to the drive; this could be a problem unless the ship materials are very resistant to radiation. Generally, considering weight as a main factor - you would have only one major set of engines. TO decelerate, turn around (easy when aerodynamics is not a factor) and fire the main motors to slow. Even mounting the main motors on full pivots means unnecessary extra hardware and weight. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [August 18, 2012, 7:16pm UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257/45 "2012-08-18T19:16:20Z")
> [@md2000](#): > > Generally, considering weight as a main factor - you would have only one major set of engines. TO decelerate, turn around (easy when aerodynamics is not a factor) and fire the main motors to slow. Even mounting the main motors on full pivots means unnecessary extra hardware and weight. The Venture Star only needed engines for deceleration. To save fuel, it was accelerated via Earth-based laser. For a ship that does need the main engines for both cases, whether you need extra engines or pivots would also depend on shielding. Interstellar ships would need quite a lot of shielding on the forward side. Pivoting the engines might make more sense than other options. Then again, the cruise phase of a journey might well last years. That might be enough time to physically disassemble the ship and reassemble it in a config more suited to the deceleration phase. Of course, you wouldn’t want to step outside the wake left by your shielding mass… ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [August 18, 2012, 7:39pm UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257/46 "2012-08-18T19:39:46Z")
The configuration of the ISV Venture Star’s acceleration sails has never been described in detail; but perhaps they would resemble a very large, circular parachute, many tens of kilometers across, preceding the ship as it leaves the Solar System, with a bright laser light (or maybe several) focused upon it to provide the thrust. The parachute could usefully have a hole in the middle, coinciding with the location of the ship, because you wouldn’t really want to be shining a propulsion laser onto the ship itself. To be honest laser propulsion is not the most efficient of the theoretical propulsion systems; better in many ways is the smart particle concept, where particles with mass are directed towards a magnetic sail and transfer considerably more momentum to the ship. You could still use an annular sail, with a hole for the ship itself, because you defintitely wouldn’t want smart, massive particles impacting the ship at respectable fractions of the speed of light. Jordin Kare’s Sailbeam concept is one of the cleverest of the smart particle systems I’ve heard of; billions of tiny, square, laser-driven light-sails home in upon the ships magsail, having been accelerated by lasers over a relatively long period. They impact the annular magnetic field and turn into energy, which pulls the ship along. I can imagine a ship very like the Venture Star hanging from a magnetic loop as a storm of smart particles rush past it on all sides towards the magsail at the front of the vessel. ---
**Author:** ![eburacum45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eburacum45/32/8690_2.png) [@eburacum45](https://boards.straightdope.com/u/eburacum45)\ **Post date:** [August 18, 2012, 7:52pm UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257/47 "2012-08-18T19:52:55Z")
A more conventional approach is being taken by the people at Project Icarus, a refinement of the old Project Daedalus concept from the seventies; [http://news.discovery.com/space/zooms/project-icarus-mission-analysis-110225.html](http://news.discovery.com/space/zooms/project-icarus-mission-analysis-110225.html) > **[Project Icarus (interstellar)](https://en.wikipedia.org/wiki/Project_Icarus_(Interstellar_Probe_Design_Study))** > > Project Icarus is a theoretical engineering design study aimed at designing a credible, mainly nuclear fusion-based, unmanned interstellar space probe. Project Icarus was an initiative of members of the British Interplanetary Society (BIS) and the Tau Zero Foundation (TZF) started in 2009. The project was under the stewardship of Icarus Interstellar until 2019. It remains a BIS project. > The project was planned to take around five years and began formally on September 30, 2009. An international ... …this is basically a fusion pulse design study, but the use of antimatter or antimatter catalysed fusion isn’t ruled out. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [August 19, 2012, 1:30pm UTC](https://boards.straightdope.com/t/best-shape-for-space-ships/631257/48 "2012-08-19T13:30:45Z")
> [@urban1a](#): > > I think the best, and most practical, design are the city shaped spaceships used by the government (Alliance?) in Firefly. They had skyscrapers and everything. Sorry, I couldn’t find an image to link to. > > Bob [Really?](http://www.pic2fly.com/viewimage/Firefly%20Alliance%20Ships/aHR0cDovL2JldGEuZmlyZWZseWZhbnMubmV0L2JsdWVzdW5pbWFnZXMvMjgzRDdCRUNCRTEwOTRCNTVERTBGNzNBRENCNzFBNkYuanBn) [Previous page](https://boards.straightdope.com/t/best-shape-for-space-ships/631257.md?page=2)