Space X to build reusable launch vehicle

charliem · Post by **charliem** » Sat Oct 29, 2011 12:20 am

You cannot get much lift from a cylinder. I bet its crossrange is not far from 0:1.

Talking about something else. In the SpaceX website I've found that Falcon 9 "entered space" a few seconds after staging. By that I suppose they mean crossing the Karman line, so the separation does not happen at 120 km but a bit under 100.

The Falcon 1 user manual states that maximum acceleration is 6.4 g, with max peaks of 7.7 g. Most probably Falcon 9 was designed to withstand more or less the same forces. This backs the number of 65 m/s2 (6.6 g) that I obtained with my numerical integration (just before the cut-off of 2 engines).

SpaceX is very private with its numbers. Don't give us much to gnaw ... although EMC2 Corp is even worse in that respect ...

hanelyp · Post by **hanelyp** » Sat Oct 29, 2011 1:52 am

On lift/drag of a cylinder on reentry (related to cross range), I happen to be toying with some algorithms for figuring that kind of thing by the Newtonian Impact Model.

Assuming a 5:1 length:diameter ratio, flat ends, my code projects a peak L/D of almost 0.4 at a 50 degree AoA.

I can share my code if anyone is interested.

Skipjack · Post by **Skipjack** » Sat Oct 29, 2011 1:54 am

On lift/drag of a cylinder on reentry (related to cross range), I happen to be toying with some algorithms for figuring that kind of thing by the Newtonian Impact Model.

Assuming a 5:1 length:diameter ratio, flat ends, my code projects a peak L/D of almost 0.4 at a 50 degree AoA.

That is indeed very interesting!
I have also been wondering why they would have to stick with the shape that they chose for the stage. Make it a little more like the DC-X and you get some nice cross range right there.

charliem · Post by **charliem** » Sat Oct 29, 2011 2:57 am

hanelyp wrote:On lift/drag of a cylinder on reentry (related to cross range), I happen to be toying with some algorithms for figuring that kind of thing by the Newtonian Impact Model.

Assuming a 5:1 length:diameter ratio, flat ends, my code projects a peak L/D of almost 0.4 at a 50 degree AoA.

Interesting, that's more than what I thought. Now the question is, how far could Falcon 9 get with that, falling from 100 km?

Skipjack wrote:I have also been wondering why they would have to stick with the shape that they chose for the stage. Make it a little more like the DC-X and you get some nice cross range right there.

I think it's because the Private Cia vs NASA philosophies I talked about a few posts ago.

In the [not subsidized] private sector they aim for shorter/cheaper hops, and before jumping again try to reuse and extend what they already have, to squeeze the last drop of usefulness from it.

Don't expect SpaceX going back to the drawing table for a radical change in the short term.

Skipjack · Post by **Skipjack** » Sat Oct 29, 2011 2:59 am

Got a point there, but is it really such a huge change compared the to the other things they are already planning on doing?

charliem · Post by **charliem** » Sat Oct 29, 2011 3:24 am

Skipjack wrote:Got a point there, but is it really such a huge change compared the to the other things they are already planning on doing?

I think it would be a big change from a costs point of view.

First the tooling for making cylinders is less complicated (cheaper) than for more exotic shapes.

Then they designed their second stage in a way that let them use the same tooling than for the first. Your suggestion would mean that'd not be possible any more.

And further, they'd have to arrange for a considerable refurbishment of their factory. More money.

All this would go against one of the main declared goals of SpaceX: build cheap.

Skipjack · Post by **Skipjack** » Sat Oct 29, 2011 3:29 am

Good points, charliem.
I would counter that the "build cheap" idea is not so important anymore once you aim for reusability.
Either way, any even miniscule lift/crossrange is in their favor and maybe it is already good enough, or maybe they will use some sort of inflatable ballute, or something like that to help?

charliem · Post by **charliem** » Sat Oct 29, 2011 2:09 pm

Skipjack wrote:I would counter that the "build cheap" idea is not so important anymore once you aim for reusability.

Well, I think "build cheap" is not so important once you achieve reusability, but right now renouncing to it would mean accepting a higher level of risk, something SpaceX seems to be quite reluctant to do.

I'm fascinated by the simplicity of the idea Elon Musk is trying to implement: just apply to space the same simple engineering principles that the automotive industry discovered a century ago in the process of turning cars from luxury to commodity.

It's so simple, so straightforward, that I'm surprised that for the last 50 years no other entrepreneur had it:

1) Simplify
2) Standardize
3) Reuse (from tooling to design, to materials, etc.)
4) Aim for high volume
5) Improve slowly but continuously, make it part of the process
6) Quality control is paramount
And so on.

Nothing new under the sun. Why neither NASA nor ESA or the Russians, or Boeing, or Lockheed Martin, have ever tried it?

P.D. Has anyone researched the possibility of standardizing space probes, to design something that could be used to visit the orbit of Venus, or Mars, the asteroids, sun's polar orbits, a few NEO objects, etc., or an exterior system probe, able to travel to Io, Saturn, or even the Kuiper belt?

Skipjack · Post by **Skipjack** » Sat Oct 29, 2011 4:10 pm

Has anyone researched the possibility of standardizing space probes, to design something that could be used to visit the orbit of Venus, or Mars, the asteroids, sun's polar orbits, a few NEO objects, etc., or an exterior system probe, able to travel to Io, Saturn, or even the Kuiper belt?

Von Braun had some concepts in that direction (use various numbers and combinations of standardized components for interplanetary spacecraft)

Btw, I think you are right about this approach (the 6 points) being the best one and that that is most likely what SpaceX is doing.
So yeah, it would probably not be a good idea to change the shape of the first stage to much.
What about the ballute though?

GIThruster · Post by **GIThruster** » Sat Oct 29, 2011 4:46 pm

charliem wrote:Has anyone researched the possibility of standardizing space probes, to design something that could be used to visit the orbit of Venus, or Mars, the asteroids, sun's polar orbits, a few NEO objects, etc., or an exterior system probe, able to travel to Io, Saturn, or even the Kuiper belt?

Yes. The trouble is with energy and propulsion. The science package can be very close to the same for all these uses and then some, and have a lot of utility added as well. It's the mission profiles that are so very divergent that they require different energy and propulsion. If we had a standard "warp core" or some such that included a power system robust enough to provide all power for say a decade at a time, then we could do just as you say and the savings would be enormous. You would need to start though, with something close to JIMO like abilities.

This is one reason I'm still interested in BLP. If their CIHT reactor were to deliver as promised, a handful would be enough for JIMO type missions and since they produce plasma, they could be used to feed VASIMR. VASIMR's real trouble is its power requirements to create plasma, so these two technologies working together could yield significant synergy. Add to these two an M-E warp core and indeed, you have all the makings in hand to standardize interplanetary and interstellar probes--and you can launch direct from the Earth--no rockets required.

Of course, it's quite possible we'd have M-E inertial thrusters before warp cores, so VASIMR and CIHT might not be needed at all.

GIThruster · Post by **GIThruster** » Sat Oct 29, 2011 4:51 pm

charliem wrote: It's so simple, so straightforward, that I'm surprised that for the last 50 years no other entrepreneur had it:
1) Simplify
2) Standardize
3) Reuse (from tooling to design, to materials, etc.)
4) Aim for high volume
5) Improve slowly but continuously, make it part of the process
6) Quality control is paramount
And so on.
Nothing new under the sun. Why neither NASA nor ESA or the Russians, or Boeing, or Lockheed Martin, have ever tried it?

Because they're spending other people's money. Until recently, ULA has not had to compete, so there was no market force to drive innovation. Probably, anti-trust laws ought to have stopped the unholy alliance between Boeing and L-M and forced them to compete. Now that there are other players like SpaceX, there are market forces working and it seems Boeing is looking at some innovation. Probably L-M is too, but I'm not aware of any specific projects.

Luzr · Post by **Luzr** » Sat Oct 29, 2011 5:26 pm

hanelyp wrote:On lift/drag of a cylinder on reentry (related to cross range), I happen to be toying with some algorithms for figuring that kind of thing by the Newtonian Impact Model.

Assuming a 5:1 length:diameter ratio, flat ends, my code projects a peak L/D of almost 0.4 at a 50 degree AoA.

I can share my code if anyone is interested.

What I would do is to add some small composite wings, possible with symmetrical airfoil (as not to influence the way up too much), at the right place of the cylinder. I believe it could be done with relatively small costs and would increase L/D to 2-3, good enough to make the way back only using the aerodynamics.

Skipjack · Post by **Skipjack** » Sat Oct 29, 2011 5:40 pm

The problem is that everything that adds to lift also adds to drag...
This is why I am thinking about ballutes or something else that is extendable...
Maybe they could do something like the extendable foils that TGC rockets has been proposing for their Michelle B rocket (wonder whatever happened with that).

DeltaV · Post by **DeltaV** » Sat Oct 29, 2011 5:54 pm

Skipjack wrote:The problem is that everything that adds to lift also adds to drag...
This is why I am thinking about ballutes or something else that is extendable...
Maybe they could do something like the extendable foils that TGC rockets has been proposing for their Michelle B rocket (wonder whatever happened with that).

viewtopic.php?p=70833&highlight=#70833

Luzr · Post by **Luzr** » Sat Oct 29, 2011 6:35 pm

Skipjack wrote:The problem is that everything that adds to lift also adds to drag...

That is why I talk about symmetrical section. Those are sections typically designed for tail surfaces, with minimal drag at zero lift at zero angle of attack. But they still can have quite good L/D with non-zero angle, typically about 30.

Something like

http://www.worldofkrauss.com/foils/1856

Adding small delta shaped wings somewhere at CG of stage cylinder with moving surfaces to stear the thing would dramatically increase gliding capabilities without adding much drag on the way up.

Admitedly, the problem is structural integrity and heat on reentry...