Kerbal Space Program

Kerbal Space Program

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SSTO Alpha I mk2
   
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Craft
Craft Type: Plane
File Size
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150.991 KB
23 Aug, 2019 @ 2:42pm
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SSTO Alpha I mk2

Description
Kerbin SSTO Alpha I mk2
6.8t to 100km orbit (max mass 30 500 kg)

The Alpha I mk2 spaceplane is a Single-Stage-to-Orbit, probe controlled craft capable of lifting 6.8 tonnes into a 100 km orbit above Kerbin. With the payload and main engines centred the craft is well balanced and easy to control at all stages of flight.

The Alpha I mk2 replaces the J-X4 Turbo Ramjets with CR-7 R.A.P.I.E.R. engines. These more powerful, dual-mode engines mean the LV-T45 rocket can be downgrades to a LV-909. The smaller rocket eliminates the mk1 largest weight imbalance making the mk2 even smother to fly. The extra power also allows for a cargo bay 50% longer.

Flight Notes
While the CR-7s are capable of closed cycle operation, the LV-909 is significantly more fuel efficient. Thus for the final assent and manoeuvres in orbit it is recommended to use the LV-909 only.

Thanks to the Alpha's large wing area it can slow down quickly during re-entry. While the suggested profile is quite shallow to conserve fuel, a steeper path utilizing a higher angle of attack is possible.

The suggests re-entry profile will overshoot the landing site slightly. Once speed drops to mach 4.5 (1500m/s) pitch up to increase drag as needed to reach the target. Fuel margins are tight on the Alpha so it is better to come in a little high and circle down than to need to use the jet engines to travel.

If coming in short and the jets are needed, use them as high up as possible where the atmosphere is thinner to make better use of the limited fuel.

Fuel Balancing
For even better performance, during re-entry watch the control deflection applied by SAS to maintain pitch and trim the centre of mass position by pumping fuel between the forward and aft Mk2 to 1.25 Adapter Long tanks. If SAS is pitching away from prograde, move some fuel aft to lessen how much pitch is needed; however, if SAS starts pitching towards prograde it means the craft is unstable, immediately move fuel forward.

Stats
Payload Capacity: 6.8 t
Cost: 50 162.3

Parts: 56
Mass: 23 658 kg
Height: 4.9 m
Width: 12.5 m
Length: 21.0 m

Jet Engines: 2x CR-7 R.A.P.I.E.R Engines
Rocket Engine: 1x LV-909 “Terrier” Liquid Fuel Engine

RCS: yes
Power generation: OX-STAT solar panels
Reaction wheels torque: 30 pitch, 18 yaw and roll

ACTION GROUPS
4 - cargo bay doors
5 - flaps inner [100%]
6 - flaps/aerolons outer [40%]
7 - intakes
8 - LV-909 engine
9 - CR-7 engines
0 - CR-7 mode & intakes

FLIGHT PROFILE:
- Extend flaps [5, 6]
- Start CR-7s [STAGE]
- Takeoff rotation at 70m/s for full load
- Retract flaps [5, 6]
- 10 degrees pitch until max speed
- Engage LV-909 [STAGE]
- Switch CR-7 to closed cycle and close intakes [0]
- Shutdown CR-7 upon Ap reaching 50km [9]
- Level to prograde upon Ap reaching 60km
- Cut throttle upon Ap reaching desired
- Circularize

RE-ENTRY:
- Lower Pe to 45km over landing site
- Shutdown LV-909 [8]
- 25 degrees pitch until speed drops to mach 4.5 (1500m/s)
- Transfer fuel between fore and aft tanks to trim pitch control
- Restart CR-7s [9]
- Switch CR-7 to air breathing and open intakes [0]
- Deploy Flaps as needed [5, 6]
- Final approach at 75-125m/s
- Aim to land at 40m/s