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.