In space vs. In orbit

Somebody asked me a bit ago why getting into space was easier then getting into orbit. The answer is a little complex and requires us to first define what each one actually is.

The actual point at which space begins is different depending on your point of view.
(From http://www.space.edu/projects/book/chapter3.html)
-At 18,000 feet, a pilot in an airplane without supplemental oxygen will begins to suffer hypoxia and be rendered unconscious within 30 minutes.
-At 9 miles altitude (47,520 feet) supplemental oxygen is no longer enough and the cabin of the aircraft (or the pilots flight suit) must be pressurized.
-At 15 miles (79,200 feet) the cabin pressurization is no longer efficient. This is because most aircraft compress outside air and pump it into the cabin or suit. At this altitude, there is not enough oxygen and nitrogen in the outside air to compress and still sustain human life. Therefore any aircraft at this altitude must have its own pressure and oxygen independent from the outside air. As far as a doctor is concerned, this is the beginning of space.
-At 20 miles (105,600 feet) turbojet engines begin to fail. There is not enough air to mix with the fuel for sustained combustion. At this point an aircraft must bring along its own oxidizer to mix with the fuel, and we call these rockets. For somebody working in propulsion, this is the beginning of space
-At 62 miles (327,360 feet) aircraft control surfaces no longer function to control the vehicle as there is not enough air pressure to create lift or drag. From an aerodynamic point of view, this is the beginning of space.

Last year Burt Rutan finally won the Space X-Prize. Some of the requirements for this contest was that the vehicle had to achieve an altitude of 62 miles, land back on earth, and then return to that altitude within 2 weeks, therefore producing a privately funded, reusable earth-to-space vehicle and opening the door to commercial space tourism.

And then last week Space Exploration Technologies made their first attempt at launching a spacecraft into orbit. If (more like, when) they achieve this, it will be another worlds first. It also a much more difficult feat. So how how is this different than what Burt Rutan already accomplished? This is where the definition of “orbit’ comes into play.

Being in orbit is basically falling towards the earth, and missing it each time. Isaac Newton once drew a nice diagram that shows this principal pretty well:

imagine a very large mountain poking up from the earth. On top of this mountain is a huge and infinitely powerful cannon. The person firing the cannon increases the amount of powder with each shot, adding velocity to each successive cannonball. Each time, the ball goes further until finally, at a certain velocity, the ball is moving so fast and going so far that it completely misses hitting the ground, and instead makes a complete circle around the earth.

In order to achieve orbit around Earth, a spacecraft needs to obtain a speed of 17,500 miles per hour or roughly 5 miles per second! At that speed a spacecraft will make one complete orbit of the Earth every 90 minutes, and in any 24 hour period it will orbit 16 times. This is what makes getting a space vehicle into orbit so difficult. The amount of energy required to lift even a small payload into orbit is tremendous. For example, the Saturn V used to launch to Apollo missions to the moon produced 7.6 million pounds of thrust (the Shuttle does not produce nearly as much thrust. The 3 main engines on the shuttle produce 1 million pounds of thrust combined, and each of the solid rocket boosters produce 1.5 million pounds for a combined total 4 million pounds) which is massive compared to, for example, the engines on a Boeing 747 which produce about 56,000 pounds each, or 224,000 pounds total.

In fact, the difficulty in achieving the minimum speed need in order to reach orbit with any significant payload is so great that those launching the rockets take every advantage they can. This is why NASA launches from Florida. Cape Canaveral is the closest point in the USA to the equator. The closer you get to the equator, the faster you are already moving because the Earth is spinning. Think of a bike wheel. If you hold onto the axle and give the wheel a spin, you can tell that the rubber part of the wheel is moving a lot fast than the spokes near your hand. The same principle holds true for the Earth. At the equator, the surface of the earth is moving along at over 1000 mph, in Florida it’s closer to 800 mph. The launch designers use this “free” momentum by launching the rocket in the same direction the Earth is spinning, thereby adding the 800 miles an hour to the craft right away.

Compared to all this, just “getting into space” is relatively easy. In fact pilots have been shooting their rocket powered aircraft (in the form of the X-15) into space for many years before we ever achieved a single actual orbit. They just dropped their planes from the bottom of a B-52, lit the rocket engines, and pulled the stick back. This is essentially what they did with Burt Rutans SpaceShip 1 vehicle as well. The only difference between it and the X-15 flights is that SpaceShip 1 was privately funded.

And who knows, maybe someday we’ll all get to travel into orbit aboard a commercial rocket, how cool would that be?

SpaceX

A few days ago a company named Space Exploration Technologies attempted to launch a brand new lifting vehicle into orbit. Named the SpaceX, this rocket was unique in that it was the first privately funded spacecraft of it kind. Unfortunately, things did not go well for them. Within the first minute of powered flight a fire caused by a fuel leak cut into the helium pneumatic system, which caused the fuel valves to close, shutting down the main engine. The vehicle proceeded to climb for a short period of time due to the momentum it had, but eventually crashed back to earth a mere 250 down range from the launch site. You can see the fire in this image:

It’s too bad the rocket was lost, along with it’s payload. But the company is detiremined to find the cause of the fuel leak, fix it, and get into space. And that’s too cool.

Good luck SpaceX!

NASA’s future

So I’ve been reading on the Bad Astronomy/Universe Today message boards (www.bautforum.com) and have some thoughts on what I hope is the future of NASA. A couple years ago President Bush (in a rare stroke of genius…VERY rare) ordered NASA to send man back to the moon, and beyond to Mars. At the same time, the US government has REDUCED NASA’s budget! (ok this sounds more like the Bush administration, order you to do something and not give you the means to accomplish it), So what does this mean? This means the science mission NASA has been planning are on the cutting block. The money to go to the moon has to come from somewhere, and Griffin is doing what he can.

What I don’t understand is why we are still absolutely throwing money at the STS (Shuttle Transportation System) and the ISS (international Space Station) when they are, really, nothing more than money pits. Here’s why I think that:

The Shuttle fleet is currently not cleared to fly due to issues with the foam insulation on the main tank. NASA is spending millions of dollars fixing the foam when there are not many flights left in the STS program anyway. What will happen if we discontinue the STS program? Well that would be the end of the Hubble Space Telescope for one. The HST depends on shuttle flights to maintain the systems and update the hardware/software. It would also mean there would never again be a full crew on the ISS as the STS is the only system able to put more than a couple astronaut/cosmonauts into LEO (Low Earth Orbit).

This brings us to the ISS. For the last 4 years or so there has only been a maintenance sized crew onboard the ISS. Basically only about 2 people at a time. With that size crew it takes most of their time just maintaining the systems, and the only reason they’re maintaining the systems is to support themselves. Quite a circle. And again we’re dumping millions of dollars into this program. What would be the result of canceling the ISS? Well, we wouldn’t have a permanent human presence in space. And with the STS program cancelled, there wouldn’t be an Americans in space at all. But keep in mind, the Russians are still flying in space (in fact if it weren’t for the Russian space program the ISS would not have been manned at all since the Columbia disaster) and so are the Chinese. Also, it appears Brazil is about to put their first citizen into space, although he will be going up aboard a Russian launched vehicle.

What I wish would happen? I wish NASA would go ahead and cancel the STS and ISS programs. I know that there is a lot of sentimental reasons for keeping these programs going, but the truth is there’s not really any reason for it anymore. These programs have now completed their missions. What NASA needs to do is continue funding the science programs that have taken a back burner. They also need to develop a new Heavy Lift Launch Vehicle (HLLV) in order to make getting back to the moon, and ultimately Mars, more efficient.

We need the science to drive discovery and exploration and to fuel our dreams about intelligent life outside our Solar System. And we need to get to the moon, eventually to Mars in order to make the next Giant Leap for Mankind. I just hope NASA sees this before it’s too late.