The THS Spaceship Thread

[Nelson Cunnington]

Originally Posted by thtraveller

How do you make a ship that is balanced for one drive also be balanced for two? If the thrust axis for one drive is through the middle of ship how can the thrust axis for the other (and both) also be through the middle of the ship? Especially when the drives have different thrusts.

I wonder why everybody assumes that when you buy the drives for a large spacecraft, they necessarily have to be large single units. If the usual arrangement is actually four drives mounted in a square formation, then in this case the vessel might have 4 of one type and 4 of another, alternating around an octagon. (Or maybe a tight packed square for one type surrounded by a looser square of the other.)

Actually, my prefered arrangement would be five drives in a cross, normally. That way, the craft can accellerate using one drive (the centre one), two drives (either balanced pair of the outer drives), three (combination of the previous two options), four (all the outer drives), or five (all the drives). This would allow some acceleration even if one or two drives were inoperable, for example.

I wouldn't anticipate that constructive interference would be any more of a problem than it is for maritime ships with more than one engine. Even a single engine would have to be mounted in such a way as to minimise vibration to the craft as a whole. Still, "tuning" the drives might be worthwhile....

[thtraveller]

Originally Posted by Nelson Cunnington

I wonder why everybody assumes that when you buy the drives for a large spacecraft, they necessarily have to be large single units.

Because realistically each NP engine needs a very large drive bell to shape the magnetic field - without itself melting from the radiated heat.

Multiple engines imply a huge backend to the spacecraft so that the drive bells can be spaced far enough apart to not interfere with each other magnetically or cause hot spots that would melt the bell. That means additional mass and additional engineering problems.

[Nelson Cunnington]

Originally Posted by thtraveller

Because realistically each NP engine needs a very large drive bell to shape the magnetic field - without itself melting from the radiated heat.

Multiple engines imply a huge backend to the spacecraft so that the drive bells can be spaced far enough apart to not interfere with each other magnetically or cause hot spots that would melt the bell. That means additional mass and additional engineering problems.

That may be realistic -- not being a fusion drive engineer, I can't really say -- but the TS spacecraft design system allows you to buy a 1-ton fusion drive, and even with a higher lower limit, SDVs are one of the larger classes out there, so one could still reasonably expect that smaller engines would be available than one enormous SDV-sized drive.

Spacing several drives far apart shouldn't imply any larger mass than one centrally located. Maybe less so, considering that the effective weight of the craft will be borne at several points rather than just one.

As to magnetic effects, I think that if there's enough engineering nous available to build a 1-ton drive, there should be enough to design the fields so that they don't interfere with each other, maybe just by making sure that they aren't all on for the same 0.001 second period of pellet ignition. (Actually, I think the effective ignition period is less than that, but I can't find my Project Orion book just now....)

[Kitsune]

Another spacecraft design. This time an AKV, a little competition for the ubiquitous Nanodynamics SIM-7 Predator. :)
Numbers and values are checked and should be in order.


System Technologies spaceship construction sub-division Astrion had been founded as part of the consolidation of the transnational. The first spaceship design it created was the MRF-1 Griffin (or Greif) which was ready for sale from 2096 on, and is meant as a direct competitor for the famous Nanodynamics Predator. Compared to this AKV the Griffin has a slightly improved sensorsuite and higher maneuverability at the cost of overall armor protection.
The Griffin design is a smoothly streamlined, slightly flattened cylinder (to fit better onto external cradles), 43 feet long with an average diameter of 10 feet, the foldable radiator wings are 30 feet times 25 feet in area. The size proved to be somewhat of a problem: the Griffin is about 15% larger than the Predator (five and a half feet longer) and the AKV holding bays of many military spaceships are designed with the exact size of the Predator in mind. The usual payload of a Griffin AKV is 9.5 tons (one coilgun ammunitions pack, either KKMP or XLMP).


System Technologies Astrion MRF-1 Griffin (Greif)

Crew:
Unmanned. Infomorph uses Astrogation, Electronics Operation (Communications), Electronics Operation (Sensors), Gunner (Railgun) and Piloting (High Performance Spacecraft). Infomorph occupies the mainframe in the unmanned controls.

Design:
Streamlined cylinder hull (10’ x 43’, 6.88 spaces, nanocomposite, extra-heavy frame, smart); cDR/cPF 70/5F, 5/1S, 10/1B (nanocomposite armor). Hull radiators (1.25 ksf), folding radiator wings (30' x 25', 1.5 ksf). Chameleon surface.

Modules:
New unmanned controls; small fixed ladar [F]; small fixed radar [F]; small PESA; coilgun [F]; 3.5 compact HT fusion pulse drive; 1.5 tanks (ultralight, nuclear pellets).

Statistics:
EMass 75.35t. CMass 93.85t. LMass 102.85t. Cost 32.08 M€. cHP 90. Size Modifier [Hull] +2/+5, [Radiators] +4. HT 12. Maintenance Interval 7.06 hours. RRA 2.5.

Performance: sAcc 0.45 G. Burn Endurance 1.79 hours. Burn points 2900. Delta-V 8.8 mps. No airspeed.