Space express airlines orbital tourism challenge closed

[Flying dutchman]

hello everyone.

 

i'm sorry but i would like to close this challenge. i thought that i could review craft on a regular basis, but this it turns out is not for me.

 

i'd like to thank everyone for their greatly innovative submissions and i hope you all had a lot of fun.

 

i'm sorry for letting you down and i hope you all can forgive me.

 

 

greetings and sincere apologies,

 

Flying Dutchman

[AeroGav]

I think it's best to update the first post in the thread as I didn't read all the posts before starting something.      I spent a couple of hours on it trying (once again) to come up with a satisfactory vertical launch spaceplane.

No air breathing engines.     The orbiter itself has a pilot and ten passenger seats. a NERV under each high mount wing.         The main boosters have Reliant engines fed by a pair of FT800 tanks strapped to the sides of the NERV nacelles.    The Reliant stage is not recoverable.     It does not have the TWR for vertical launch however, so the first few seconds are assisted by a pair of Fleas.    The Flea stage have parachutes on them and jettison so low that they can land before the airplane goes out of physics range.   Won't save much money,  bur it's something.

The fleas boost us to an incredible 44 m/s and 160m altitude.. 

Reliant power for the masses.   You can see the separatrons on the nose of the boosters.   They yaw the nose outwards and downwards on separation, which causes aero forces acting on the body of the booster to push it further outward and down.    The boosters get us to an altitude where the NERVs can work well, and through the sound barrier, but that's about  all.

It's not easy to build something out of multiple Big S wing parts that still looks ok.   Dry wings would mean i need cylindrical tanks to store the fuel which would add drag however.

 

Safety Features

There is a ballistic recovery chute mounted to the upper fuselage.   The abort button could be triggered to lower the landing gear, release the chute and fire the separators for all boosters.     Between the recovery chute,  ability of this craft to glide, low stall speed,  landing gear , 40 m/s impact tolerance of crewed parts,   and the crumple zone surrounding the crewed stuff,   loss of all propulsion should be fine whether it happens 3 seconds , 30 seconds or 3 minutes into flight.

There is an inline clamp o tron ahead of the cockpit, which can be used to transfer crew to another vessel should the orbiter have a fault that prevents safe re-entry.   However it is not outfitted with an RCS system which precludes routine use.   The orbiter would simply rendezvous with the rescue vessel and passively allow a full translation space tug dock to it.

 

Design Issues,  work in progress

I really hate seeing wings go unused during the ascent, such a waste of mass ! In this vessel's case,   the lift to drag ratio they have enables it to fly to orbit with a TWR under 0.5 ,   so long as the booster gets it to 400 m/s and 8km altitude.   In turn,  the low TWR requirement means we can use hyper efficient NERV engines,   and put most of our fuel in the wings.

The biggest issue is that the orbiter stage, under nerv power,  flies at a 5 degree angle of attack with the nose about 7 degrees above the horizon, for perhaps a 2 degree climbing angle.    The booster prefers a 30 degree climb angle and of course launch with the fleas is vertical with TWR > 1.   Fairly aggressive maneuvering is required.   Below 100 m/s in the booster phase it wants to lawn dart so full back stick,  then it starts wanting to pitch up more and more due to the lift , and towards the end of the booster phase you need to start flattening out the climb angle to something more suited to flight on NERV power so you're banging the stick forward.  

The wing is mounted high on the fuselage to make room for the boosters, which means most of our fuel is above CoM.  Causing a pitch up effect from the NERVs.   If you climb at too steep an angle,  you'll get into a low dynamic pressure regime (high and slow) and this becomes quite noticeable.   If you climb more shallow aero forces surpress that tendency.    When  circularising it can really pitch up a lot if you bang the throttle open abruptly. 

Flight tips

As I say,  key is to not let it lawn dart after launch (pull up),  then nose down as needed to keep climb to no more than 30 degrees.   Above 7km start to push the nose down to a shallower climb (10-15 degrees).  Once on NERV power,  try to take SAS off and keep it off as long as you can to minimise drag.   It is aerodynamically very stable but the torque from the engines likes to push the nose up a bit.

Use pitch trim to maintain climb angle - ALT + S key.  To begin with, you'll be halfway up the pitch trim scale to get a 5 degree AoA,  as you get into the upper atmosphere,  you'll be winding this off as torque from engines is pushing the nose up plenty all by themselves.

https://www.dropbox.com/s/gwh3fx2dn6xjkwh/EXPRESS2.craft?dl=0