Spaceship Landing

[BackworldTraveller]

So, is spaceship landing something that happens by VTOL because they have M-Drives or does it require rolling down a runway?

I ask because many of the OTU starports seem to show runways. And yet the ships appear not to have wheels on their landing gear.

Also, if your starship lands, and has the powerplant shut down, how do you move it to the maintenance shed? Is there a ground-movement option at the bigger ports or do the maintenance guys come to the ship?

 

[coliver988]

I've always done VTOL with grav drives (and sometimes, if we're using minis, complete with whooshing sounds as they take off or land. I am easily amused)

I usually lay out at least 1 strip as the port may also be used for more normal aircraft for cargo handling. You may have a TL-12 ship with grav thrusters, but here in TL-6, cargo jets still rule for moving things a long ways away.

And out of game, they probably based the ports on existing airports as, prior to GURPS having city-sized ports, most ports in the TU I think were the small ship universe type. Need to dig up my Judges Guild Starports Guide - it had a bunch of pre-made ports. It is in that pile behind me someplace!

 

[Condottiere]

They probably have tractors with repulsor beam equipment, to move grounded spacecraft around.

 

[Xerxeskingofking]

So, is spaceship landing something that happens by VTOL because they have M-Drives or does it require rolling down a runway?

I ask because many of the OTU starports seem to show runways. And yet the ships appear not to have wheels on their landing gear.

Also, if your starship lands, and has the powerplant shut down, how do you move it to the maintenance shed? Is there a ground-movement option at the bigger ports or do the maintenance guys come to the ship?

i personally follow the way that BattleTech does it, in that different types of DropShip make different approaches to the port. depending on if they are aerodyne (plane like) or spheroid (ie fully or partially streamlined).

aerodyne type ones tend to make rolling, airplane style landings which requires a little less engine power for the lower altitudes as you can use aerodynamic lift to support you (to a degree), and aerodyne craft have the control at low speed and altitude to actually make a rolling landing. However, most aerodyne designs have the thrust power to make a VTOL type landing if needed, as not everywhere has a atmosphere that can support flight. Also, in real life at least, VTOL aircraft can take off at a heavier weight using a rolling start than they can via a VTOL take off, so heavier ships with less powerful engines might find it beneficial to make a rolling takeoff.

spheroid type ships basically have to land like the Apollo landers or the SpaceX rockets, riding their drives down into a vertical landing on the pad. it requires some pretty careful piloting for the final touch down, and if its not properly balanced it might fall over (although this is more a problem with tall thin "tail sitter" designs in real life than most traveller ships), and a 1G drive craft might need to overclock slightly on the approach to slow down enough (or rely on aero-breaking to slow, with all the issues with heat build up that go with that).

Once a semi-steamlined ship has entered the atmosphere they don't really have the control ability to radically alter their coruse like a plane could, they are basically on a ballistic course to their destination, or if they have the thrust they can abort back to orbit. If you have ever played Kerbal Space Program, it would be like that: you can adjust "long" or "short" fairly easily (assuming you have the 2 or 3G engines) but a significant change "left" or "right" would require a lot of engine power, burn time, and may simply not be possible at lower altidudes because youd need to thrust that far off-axis your craft would tumble and lose control.

Assuming you've come down on target you would be approaching the spaceport in a near-vertical drop, with fairly little relative movement sideways, and you'd basically plan to drop more or less straight down into your landing bay.

now, the two methord have very different approach routes form orbit, and it might be beneficial to have the options to support both approaches as a way of controlling traffic, letting you get more ships down faster as you can have two queues coming in to land, one to the runway and one to the vertical pads.

 

[AnotherDilbert]

So, is spaceship landing something that happens by VTOL because they have M-Drives or does it require rolling down a runway?

Either.

You normally need more thrust than local gravity to land or take-off. Worlds size 8+ has 1+ G local gravity. No normal populated world has 2 G or higher. Spacecraft with 1 G have a problem.

Winged spacecraft can suppleant aerodynamic lift for missing drive lift, about an additional 1 G lift.

So to land everywhere you basically need 1 G + wings or 2 G. Landing with wings require a landing strip.

Spacecraft might be able to land anyway, but very, very slowly and carefully, although I have no idea how that happens.

See e.g. T5.10 B2p103.

 

[Condottiere]

Depending on whether you believe ten percent vectoring is possible vertically, the more probable solution would have been auxiliary gravitational motors configured as lifters.

 

[BRover]

. . .
You normally need more thrust than local gravity to land or take-off. Worlds size 8+ has 1+ G local gravity. No normal populated world has 2 G or higher. Spacecraft with 1 G have a problem.

Winged spacecraft can suppleant aerodynamic lift for missing drive lift, about an additional 1 G lift.

So to land everywhere you basically need 1 G + wings or 2 G. Landing with wings require a landing strip. . . .

This is exactly why I find the 20 dTon Lifeboat/Launch rather unlikely. A 30 ton Ship's Boat can do 6G, and the 20 ton craft is limited to 1G? Why?? At least give it 2G, and a much improved survivability.

Especially if, (LBB2 '81), the Boat and Slow Boat cost MCr 16-15, and the Launch only MCr 14. So, for a whole MCr1 cheaper, you lose 2G and 10 tons of ship.

 

[aramis]

Runways make a great backup for aerodyne takeoffs...

 

[AnotherDilbert]

This is exactly why I find the 20 dTon Lifeboat/Launch rather unlikely. A 30 ton Ship's Boat can do 6G, and the 20 ton craft is limited to 1G?

Agreed, that is very limiting.

As a Lifeboat it is perhaps not intended to land. Fill it with low berths, kick it out into space, deploy some solar panels, and it can survive for decades.

Yes, the cost is puzzling, as it would cost MCr 5.5 with identical performance if made with LBB5, as the LBB2'81 small craft seems to be. And it would only cost 0.2 Dton to increase acceleration to 2 G.

A reasonable small utility craft would be something like this:
20 Dt, 2 G, 12.5 Dt passengers/cargo/fuel, MCr 6 in quantity.

GL-0202201-000000-00000-0        MCr 5,8          20 Dton
bearing                                            Crew=1
batteries                                            TL=9
                          Cargo=0 Fuel=1 EP=0,4 Agility=2

Single Occupancy                                    0,2       7,2
                                     USP    #     Dton       Cost
Hull, Streamlined   Custom             0           20            
Configuration       Cone               2                      2,2
                                                                 
Manoeuvre D                            2    1       1         0,7
Power Plant                            2    1       1,2       3,6
Fuel, #J, #weeks    J-0, 4 weeks                    1            
                                                                 
Bridge                                      1       4         0,1
Computer            m/0                0    0                    
                                                                 
Couch                                      25      12,5       0,6
                                                                 
Cargo                                               0,2          
Collapsible Tanks   13 Dton                 1       0,1       0,0
                                                                 
Nominal Cost        MCr 7,23             Sum:       0,2       7,2
Class Cost          MCr 1,52            Valid      ≥0          ≥0
Ship Cost           MCr 5,79

 

[BackworldTraveller]

How much space would landing gear need for the small craft?

For a large craft (e.g. 10,000dtons) would this scale linearly?

Would the FFS wheeled suspension work as an estimate? Is it part of "Bridge".

 

[AnotherDilbert]

How much space would landing gear need for the small craft?

Depending on edition: CT-T4 doesn't bother with such small details (cost = 0 Dt), T5 has specified costs for different types of landing gear.

FFS Wheeled suspensions is for vehicles, e.g. armoured cars. I would not apply that to spacecraft landing gear.

The bridge is C³I equipment and crew stations, not landing gear.

 

[AnotherDilbert]

Depending on edition: CT-T4 doesn't bother with such small details (cost = 0 Dt), T5 has specified costs for different types of landing gear.

FFS Wheeled suspensions is for vehicles, e.g. armoured cars. I would not apply that to spacecraft landing gear.

The bridge is C³I equipment and crew stations, not landing gear.

I would say that folding landing gear is a part of the cost of streamlining.

 

[Condottiere]

You could have tugs and rocket assist.

In the end, you probably needed to make an cost benefit study as to which performance configuration optimizes return on investment.

 

[BackworldTraveller]

This also begs the question of Gas Giant refuelling...There is a widespread assumption that just anyone can do this, but I suspect that, for anyone with less than 2G acceleration, this is a one-way trip to hell - and with only 2G its a hazardous procedure with overloaded drives trying to battle against gravity.

How does everyone else play this?

 

[mike wightman]

All you are doing is adjusting your orbit so it passes through the upper atmosphere of the gas giant. This doesn't require much in the way of deltaV to achieve, and even a 1g magic maneuver drive is more than sufficient for the task.

 

[AnotherDilbert]

You do not stop in the GG, you just make a high speed pass through the upper atmosphere.

Gas Giant Fuel Skimming is orbital in nature; the ship is not landing and restrictions based on drive acceleration do not apply.

Basically you can start with a circular orbit, manoeuvre to make the orbit elliptical so that a small part of the orbit dips into the atmosphere. You follow an orbit that will lift you out of the atmosphere even without applying more acceleration, despite the aerobraking.

Vaguely like this:

 

[BackworldTraveller]

I'd have thought that if you are going fast enough to escape and you go deep enough to gather a meaningful volume of fuel, the drag is high enough to (a) slow you below the critical value and (b) melt you due to friction. The energy transferred from the atmosphere to the ship looks to me not so far off that that which a weapon would inflict.

 

[AnotherDilbert]

It's a balance: the upper atmosphere is very thin, only the speed makes you pass through enough of it to collect enough fuel.

Go through to high and the atmosphere is too thin; you can't get enough fuel.

Go too low and the atmosphere is too thick; the friction kills your speed and heats your hull too much.

 

[G. Kashkanun Anderson]

It also really depends on the gas giant. Most 'gas giants', in the Traveller sense, are actually ice giants (Uranians and Neptunes), with relatively puffy atmospheres and reasonably navigable gravity wells. Jovians are relatively rare in the universe (about one in ten for a Sol-like star, significantly less for anything smaller); and even then, there is likely to be an ice giant in the system as well. So you would typically have choices available to match your ship's capabilities, though some of that may well depend on how far out into the system you are willing to venture.

Ice giants like Neptune should be pretty trivial for a properly equipped 1g craft to handle. Even Saturn should be fairly easy, as its 'surface' gravity is not much more than Earth's. Jupiter is where it gets challenging, as a 1g ship would have to rely on momentum or a good lifting body in order to get anything done. Anything above Jupiter would require stronger engines or a crazy-good pilot, and anything well into the superjovian range (above 3 Jupiter masses or so) would be regarded as near-suicidal at current Imperial tech levels, as the usable atmosphere on those worlds rests deep inside their gravity wells,* where the g's are at double digits.

*Except for Hot Jupiters, which are likely unusable for other reasons.

 

[Condottiere]

One gee would probably have been short haul commercial.

But with a gravitationally motivated constant acceleration, it should compensate as you ellipse around the free gas watering hole.