KerbalX

Details

• Type: SPH
• Class: spaceplane
• Part Count: 354
• Pure Stock

Hearts Chevron 96 Intro

Hearts Chevron 96 Cargo Lifter. Hearts Chevron is named by the shape of the engine blocks that form a heart or chevron pattern. In flight it forms this unique contrail pattern. The 75MC version standing for 7.5meter center referring to the 7.5m fairing center cargo hold.
It has 96 rapier engines hence the number 96. It can lift up and carry 1450Ton+ to orbit with a payload fraction of 51,5%
One rapier will carry 28.5Ton of weight.
I made this space plane so I can use a single version to haul almost any volume or weight to LKO for superb fuel economy. It is only meant to be used as such, namely a cargo SSTO to and from LKO. Only intend to haul cargo to 71-75/71-75km orbits unless you can’t resist.
Make sure the cargo is distributed evenly and that it is moved so that the center of mass is below the center of lift (directly).

IMPORTANT

Read instructions down below to fly successfully.

Flying the vessel could be easier, however, my intention was to make a cargo SSTO that can haul cargo of most shapes and sizes.
Some cargo have a very wide construction with very heavy weight on one side.

Or your cargo makes the CoM jump down due to very low hanging mass, odd shape or design construction.

Therefore I mad a engine bay in the middle to allow Center of Thrust control to accommodate aerodynamic unbalance if custom cargo is of odd design. Several action groups control the thrust setup that complicate the piloting.
Because of this setup the wings are placed high and the flight characteristics are a little different whereby aerobraking requires special input to control properly, but is ultimately very straightforward.

Securing vessel rigidity may become riskful using stock SAS when using fast and immediate turns or control input at high speeds especially when payloads
past 1100Ton are used. While it is safe to use the max payload it requires you to pitch gently through the course of the flight using the below instructions.
For that reason it is best to use Mechjeb Smart A.S.S. Surface mode to navigate the space plane to orbit. The instructions below are written for stock.

INSTRUCTIONS

Instructions are a little sensitively written because sudden control inputs at high velocities using MAX cargo can result in sudden RUD. This vessel is also intended to be STOCK only so everyone can use it, using SAS only it requires proper piloting

1. Always put cargo under CoM similar to the custom cargo. Otherwise you’ll suffer pitching momentum and balance issues at takeoff. Custom cargo does not require the following. However, depending on custom cargo you may want to Hold Left Alt + W to trim the pitch down so the nose stays level after takeoff. (use Left Shift + W on Unix)
2. Full throttle and accelerate past the last 2 blocks at the end of the runway and hold S to takeoff. Get the nose as far as possible while holding down S to clear the terrain after exiting the runway. Stay near sea level to accelerate without using SAS (shouldn’t be difficult as the aerodynamics are balanced.
3. When reaching 350m/s (Trim the pitch backif used)
4. Use/Hold W, S thereafter to stay level at 0° and hold SAS stability assist and use W,S until it settles at 0°.
5. Keep accelerating but don’t touch any controls (unless you’ll rollshouldn’t happen normally) until you reach 9km altitude.
6. At 9km the nose would have naturally risen up to about 8-10°. Activate Lights Action group to deploy front spoilers for pitching balance. Pitch the nose down to 2-5° by holding W. Keep tapping and holding W but don’t hold longer then 2 seconds not to cause sudden pitch, repeat until it settles at 2-5°.
7. Keep accelerating to 20-23km altitude with the intention to achieve ~1600m/s+
8. Activate RCS to toggle fuel cells for EC generations and Action group 1 to toggle all rapiers to closed cycle mode, activate light action group again to toggle spoilers off at the front and rise nose to 10°
9. Keep at 10° until vertical climb is at 300m/s+ and hold prograde (hold S and/or W to follow prograde as SAS is stubborn.
10. Activate RCS action group to toggle Fuel cells for EC generation.
11.Use action group 3 and/or 6 to toggle engines for Center of thrust if Space plane tends to pitch up or down (depending on payload) This usually happens when nearing orbital velocity or above 31km altitude.

Tip: Spaceplane has very little cross section with a lot of weight and doesn’t slow down easily. You can get MECO at a Apoapsis of 70+ Km as low as 34Km altitude and then drift to Apoapsis without losing to much velocity.

12. Use Action group 2 through 6 i[/i] while throttling at Apoapsis to circularize. i[/i]

Tip: Keep toggling any of the engines modes on/off to keep the nose at prograde when payload requires it as there is no other means to stay oriented in the upper atmosphere/space.

Explanation

The reason I chose this method of controlling pitch on the space plane is because for large cargo, excellent performance and balanced stability throughout flight while including universal cargo types insisted to use a engine placement that was mid center.
The unfortunate side effect is that you will have to do a little bit of practice to do it right. It is very easy and straightforward when getting the hang of it. Just F5 and reload if you mess up.

13. Use the last stage to decouple cargo i[/i]
14. Rotate retrograde. Toggle off action group 3, 5 and 6 and toggle between 2 and 4 while throttling to stay balanced.
15. Dive your Periapsis as low as you want (can)
There are 2 ways to do a re-entry.
a. You can dive to your Pe while holding prograde. Wing incidence makes the space plane skip the atmosphere. If you want to reverse that effect you can roll the spaceplace on the side or back and vice versa. The spaceplane can get below 25km altitude due to heat resistance.
This way you can aim your way over the KSC and then use the brake action group to activate spoilers on all control surfaces u[/u] Alternatively you can do a Flat body aerobrake also.
b. Use 90° through 50° degree AoA depending on atmospheric height using SAS stability assist.

IMPORTANT

You will not be able to push the nose down after a flat body aerobraking unless you do the following.
Use Action group 8 to Deploy rear mounted fairing adapter and elevons near the main landing gear and push W to lower the nose then pull up using S all the way to 90° if possible and then hold W until the nose dips down to prograde.
If you don’t do this you will be in a irrecoverable flat body stall until below 200m/s. Best is to get to prograde when at or below 1400m/s. Below that speed you may need to repeat the pushing and pulling sequence a 2nd time. Think about a swing that needs to wind a 2nd time.
Activate Brake action group to deploy spoilers on all elevons before landing to lose the last 100 m/s or more.

Tip: You should be able to navigate to KSC using the methods easily, in a emergency the space plane can land on water when empty.