Archive for the ‘Rocketry’ category

New Direction for NASA

January 31, 2010

If the rumors of Obama’s NASA budget request are true, then Obama is asking Congress for what I and several other aerospace leaders have asked for. Unfortunately, not everyone is as thrilled about the rumored budget. I am firmly convinced that the rumored budget request is the best thing for NASA, human spaceflight, and the nation as a whole. This is the best approach to achieving the objectives of the former President’s Vision for Space Exploration, which outlines the objectives to reach the one goal that really matters for spaceflight – spread humanity beyond Earth.

Here is the heart of the Vision for Space Exploration from the Goal and Objectives:

The fundamental goal of this vision is to advance U.S. scientific, security, and economic interests through a robust space exploration program.
• Implement a sustained and affordable human and robotic program to explore the solar system and beyond;
• Extend human presence across the solar system, starting with a human return to the Moon by the year 2020, in preparation for human exploration of Mars and other destinations;
• Develop the innovative technologies, knowledge, and infrastructures both to explore and to support decisions about the destinations for human exploration; and
• Promote international and commercial participation in exploration to further U.S. scientific, security, and economic interests.

How do Constellation and the rumored budget proposal stack up? I will take a little risk here and assume that the new direction is the Flexible Path with commercial crew and ISS 2020 option from the Augustine committee report.

Sustained and Affordable

According to the Augustine committee, for Constellation to have any chance of getting to the Moon, we need to terminate all other HSF activities and significantly increase the budget. Even then, this is no sure thing. Constellation has already gutted critical NASA research in other areas. Jeff Greason pointed out during one of the public hearings that if Santa brought us the fully developed Constellation vehicles right now, we could not afford to fly them.

Not only can we not afford Constellation now, but also what happens in say 2030? Constellation is described as Apollo on steroids, so can we expect Congressional cuts on steroids? This seems very likely. What do we do then? Like Apollo, there will be no space faring infrastructure, and the only next step will be too expensive to consider. Constellation is not sustainable or affordable.

Flexible Path combined with new R&D and commercial LEO capability should give us a leg up. Flexible Path encourages and possibly requires the building of space infrastructure. With new (ahem, restored!) R&D money NASA can investigate the use of propellant depots and other on orbit facilities to base beyond LEO capabilities. The ability to do a number of missions to many places and not just the Moon allow NASA to investigate the concerns of long term living beyond the Earth’s influence. The balance of evidence indicates that sustainable and affordable means it must be done by commercial interests expecting to make a profit. With NASA as an anchor tenant, commercial crew providers can expand their offerings to other people, including non-NASA researchers, industry or just tourists. The commercial crew option closes the business case for commercial providers to open up LEO to people beyond NASA astronauts.

Extend Human Presence, Moon by 2020

Constellation, created as the response to this objective, cannot achieve this goal. The Augustine committee determined that by doing nothing else NASA might get back to the moon in the late 2020s. More likely it would be the 2030’s or even later, if ever. Moreover, Constellation does little or nothing for actually extending our reach through the solar system. It can only go to the Moon. Constellation was nominally designed to lead to a Mars system, but it is not clear to this aerospace professional that it does any such thing.

Flexible Path on the other hand explicitly extends our presence throughout the solar system. While it does not return us to the Moon by 2020, Flexible Path gives us the option to land on the Moon and eventually Mars when we are ready to do more than just leave flags and footprints.

Develop the innovative technologies, knowledge, and infrastructures

Constellation was according to its lead architect Mike Griffin, not going to do this at all. It was a return to Apollo era capabilities. The only knowledge development was for NASA to regain its ability to design a launch system.

This leads to a little rant – How is Ares I considered the gold standard of safety? Ares I is being designed by a group of people who have not designed and built a launch system. Ares I has no demonstrated reliability or safety. SpaceX, ULA, and Orbital are full of people who have designed, built and successfully flown orbital launch vehicles in the very recent past. ULA’s Atlas V has a better-demonstrated record than the shuttle. The cold, hard facts are that a ULA, SpaceX, or Orbital launcher is going to be safer than Ares I.

In order to do more than just leave flags and footprints on other worlds we need a space faring infrastructure. Depots and stations strategically located in various orbits around Earth, Luna, Mars and the Sun are necessary to long term exploration and eventual settlement. The Flexible Path is more likely to provide these. Commercial crew development adds the benefit that the commercial providers can get industrial concerns off the Earth and possibly into in situ resource extraction.

Promote international and commercial participation

Constellation effectively slams the door shut on international cooperation. The ISS is the basis of international cooperation in space, yet in order to do Constellation we must de-orbit the ISS in 2015, 5 years prior to the desires of international collaborators. De-orbiting ISS in 2015 will sour our partners on any new partnerships. Besides, there is little or no room for international collaboration within the Constellation architecture. Under Constellation, there is no commercial participation beyond highly directed cost-plus contracts.

Under Flexible Path with commercial crew to LEO, commercial participation is a given. With the extension of ISS to 2020 and possibly beyond, we can continue to work with our international partners, and encourage them to help out with future projects. The Flexible Path is as its name implies, flexible.  International partners can help out in ways that make the most sense for both them and us.

Conclusion

Constellation not only fails to deliver on every single goal of the VSE, it fails to advance the state of Human Spaceflight. If the rumors of the President’s NASA budget request are true, and the President is willing to fight for it in Congress, then our spaceflight future has a reasonable chance of not only surviving, but also growing and becoming much greater than we can now imagine.

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Interstellar Probe How-to Part 2.

June 25, 2009

In part 1 I described what an interstellar probe might contain, and what technologies we’d need. Here I get more into what the trajectory looks like. The calculations and estimates are all back of the envelope – i.e. they are a very rough order of magnitude estimate.

In designing a multistage trajectory, it is often helpful to start at the destination and work backwards along the trajectory to see what is needed. We’ll assume that the Gliese 581 system is our destination. It is 20.3 light years away and well off the Solar ecliptic plane. At Gliese 581 we’ll want a set of science instruments, about 10,000 kg (22,000 lbs) worth. For comparison, the entire Hubble spacecraft is 11,000 kg. We’ll need really good communications, call it 1000 kg, and a power plant to power both the instruments and radio, several small fission reactors should do well, another 10,000 kg. We’ll need a propulsion system, for that we’ll choose a Bussard Ramjet. The Bussard Ramjet is best thought of as an augmented sail. It is not capable of large velocities relative to the local space medium, but it doesn’t need to carry fuel and we’ll mostly be wandering from orbit to orbit within the star system anyway. We’ll give the engineers 20,000 kg for the ramjet. That gives us a total spacecraft mass of 41,000kg (90,000 lbs).

Working backwards, we need to slow down coming into the Gliese 581 system from our interstellar velocity. Again the Bussard Ramjet is perfect, it is just an augmented sail. Our relative ‘airspeed’ is very high, slowing down with the Bussard Ramjet is straightforward. About one half a light year out from the star, we start up the ramjet collector and by the time we cross into the Gliese 581 solar wind, we’ll be at orbital capture speeds. So we don’t need to add any additional mass or capability for this stage.

Working backwards again, we have a long coast phase. We will need small course corrections, again we already have the necessary equipment. A small (in the noise) amount of stored fusion materials can be run through the Bussard Ramjet’s fusion reactor to make any minor course changes.

Now we come back to the boost phases, and we need to work forward. We’ll start at L4. First phase is earth departure, we need to go from Earth orbit to Solar orbit. Then we need to do  plane change to line us up with Gliese 581, then do our solar departure burn. For these phases I calculate that a four stage booster system using nuclear fission fragment engines will be necessary. The gross mass of the vehicle at L4 where it starts will be 13 kilo-tonnes. For reference, this about the same size as 4 Saturn V rockets. Not small. The first stage thrust is fairly small, providing about 60 micro-g of acceleration. And the first stage will be burning for over 36 years! At staging the spacecraft will be nearly 1/2 a light year away (28,000 au) travelling at 2.5% of the speed of light. The first stage is ditched and the second stage starts its burn. After another 36 years the second stage shuts down. The spacecraft is now going about 5% of the speed of light and is 1.35 light years away. At the end of the 38 year third stage burn, the spacecraft is cruising along at 7.5% light speed and a little over 4 light years away. At the end of the 36 year long fourth stage burn, the spacecraft is moving at 10% light speed and is over 7 light years away. At this point the spacecraft coasts for about 124 years, which brings it to within about 1/2 light year of the Gliese 581 system. At this point we kick on the Bussard Ramjet collectors which slows the spacecraft down with a deceleration of 0.1 g. For ten years the spacecraft slows down and enters an elliptical orbit within the Gliese 581 system. Using the ramjet for both power and orbital maneuvering the spacecraft becomes a permanent part of the Gliese 581 system and can systematically find and observe every chunk of rock, snowball, or ball of gas in the system until it wears out.

All told we are looking at 280 years of transit time. At the end of the transit, a scientist will be getting the data she requested as a grad student when she retires! Most importantly, we will have an entirely new view on the universe.

But why only do one?

Interstellar Probe How-to

June 24, 2009

I was listening to the April 22 2009 edition of the Skeptic’s Guide to the Universe podcast a some time ago. They had on Seth Shostak, senior scientist at the SETI Institute, talking about doing an interstellar probe. In addition, Bob Novella did a blog post on the subject. The major point I got from the SGU interview and Bob’s blog post, was that Seth thinks we could do a probe to another solar system. More recently, Matt Springer at Built on Facts had some thoughts on interstellar travel as well. The reason I am only just now blogging about it is because 1. I’ve been busy at work and 2. I wanted to do more than just say I’m very skeptical of the idea. I like the idea, there is nothing physically impossible about it, so why not figure out how to make it happen and see if my feelings of skepticism are merited?

So go read (or reread) Bob’s blog post then come back. I’ll wait. Waiting…Waiting…

Back? Got it? Good.

Now remember, this whole thing is not ready for prime time, it is a crazy idea. But it might just be crazy enough to work.

We want a spacecraft that will be doing one tenth the speed of light, visiting an interesting star system with planets. Turns out there are a few such systems in our stellar neighborhood. We’ll need a really good rocket to get us up to speed.We’ll need lots of support from many people, including scientists and especially certain people in very high places. (more…)

T-7 Days And Counting.

February 28, 2009

Current schedule for the Kepler mission is for launch on March 6. Launch windows are from 10:49 – 10:52 p.m. and 11:13 – 11:16 p.m. EST. Launch is aboard a ULA Delta II.

Kepler got its payload fairing wrapped around it today. Here it is with half of the fairing:
The Kepler spacecraft in its fairing.

The Kepler mission is very important to me. This spacecraft is capable of discovering Earth-like planets around other stars. And that means updates to the Galactic Population Estimate!

Congrats to Iran!

February 4, 2009

Whoa – Iran?
Well, let’s be honest, the troubling thing about Iran is their political and religious leaders, and having spent a number of years living in a glass house, I’m not going to throw stones.

Anyway, they have launched a satellite into orbit. And that deserves congratulations, I am always glad to hear that someone put something into orbit.