Saturday, October 15, 2011

An All-Solid-Upper-Stages Booster



An All-Solid-Upper-Stages Booster
By Ed LeBouthillier

I don't want anyone to think that I'm picking on solids as being incapable for booster stages. To the contrary, they're very capable and offer many benefits of their own over liquid stages. To show their capability (and some aspects of their requirements), I'm going to do a quick analysis of an all-solid-upper-stages booster utilizing off-the-shelf solid rockets.

ATK [http://www.atk.com/corporateoverview/corpover_missiongroup.asp] produces some very high quality solid motors which are used in various military and space applications. Their 2008 catalog can be found online [
http://www.atk.com/capabilities_space/documents/atk_catalog_may_2008.pdf] so I thought I'd look at their offerings to look at what a solid-upper-stages booster might look like. Now, before you start saying "cool! let's do it," I should point out that these motors are what many of us would call "very expensive." But, they provide some ideas on what a small orbital launcher using solid upper stages might look like.

I've selected 3 ATK solid motors for the upper stages: the Star 5C, the Star 9 and the Star 15g as being representative of good solid motors suitable for this task.

This analysis has a number of caveats worth considering:

1. DELTA-V - I've only allowed for about 24500 fps (7467.6 m/s) for upper stages
2. CONTROL - I haven't included any weight for control systems (i.e. TVC)
3. GUIDANCE - No weight has been included for a guidance system

The idea in this analysis is merely to show what a small orbital vehicle might look like in a rough way.

Here are the results that I get:


Stage 4
Stage 3
Stage 2
Stage 1

Oxidizer
AP
AP
AP
Lox

Fuel
HTPB/Al
HTPB/Al
HTPB/Al
Propane


Star 5C
Star 9
Star 15G


Payload
0.250
10.110
51.111
257.707
lbs
OF Ratio
6.400
6.400
6.400
2.200

Oxidizer Density
121.700
121.700
121.700
71.23
lbs/cuft
Fuel Density
68.498
68.498
68.498
33.36
lbs/cuft
Avg Density
114.511
114.511
114.511
59.396
lbs/cuft
Average Isp
268.1
289.1
281.8
250
Seconds
Desired DeltaV
4928.1
9102
10674
10409
FPS
Body:Fuel Mass
1.2409
0.2853
0.1587
0.2467

Thrust
450
1200
1000
6350
lb-f






Payload Ratio
0.025
0.247
0.247
0.105

Structural Coef
0.554
0.222
0.137
0.198

Propellant Ratio
0.446
0.778
0.863
0.802

Mf/Me Ratio
1.771
2.661
3.245
3.648







Propellant Mass
4.400
31.900
178.300
1967.312
lbs
Oxidizer Mass
3.805
27.589
154.205
1352.527
lbs
Fuel Mass
0.595
4.311
24.095
614.785
lbs
Oxidizer Volume
0.031
0.227
1.267
18.988
cuft
Fuel Volume
0.009
0.063
0.352
18.429
cuft
Stage Weight
9.860
41.001
206.596
2452.648
lbs
MT
5.460
9.101
28.296
485.336
lbs
Me
5.710
19.211
79.407
743.042
lbs
Mf
10.110
51.111
257.707
2710.354
lbs






Max G's
78.811
62.464
12.593
8.546
g's
Cum Delta V
4928.050
14029.800
24703.410
35112.410


So, the Gross Lift Off Weight (GLOW) is about 2710 lbs (1011 kg). The payload experiences upwards of 79 g’s as the final stage is nearing empty (presuming a fairly constant near-average thrust which is what the thrust curve does show).

But, as a feasibility or model of a possible launcher, it shows what is possible. The first stage is a scaled-up Aerobee 150 sustainer. The body diameter is 20 inches, the finspan is 3 feet 11 inches and the total height is about 24 feet 2 inches.



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